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Message-ID: <2025091155-audition-nimble-4958@gregkh>
Date: Thu, 11 Sep 2025 18:20:55 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org,
akpm@...ux-foundation.org,
torvalds@...ux-foundation.org,
stable@...r.kernel.org
Cc: lwn@....net,
jslaby@...e.cz,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: Linux 5.15.193
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 0301ac606cdd..2c78f932a956 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -526,6 +526,7 @@ What: /sys/devices/system/cpu/vulnerabilities
/sys/devices/system/cpu/vulnerabilities/srbds
/sys/devices/system/cpu/vulnerabilities/tsa
/sys/devices/system/cpu/vulnerabilities/tsx_async_abort
+ /sys/devices/system/cpu/vulnerabilities/vmscape
Date: January 2018
Contact: Linux kernel mailing list <linux-kernel@...r.kernel.org>
Description: Information about CPU vulnerabilities
diff --git a/Documentation/admin-guide/hw-vuln/index.rst b/Documentation/admin-guide/hw-vuln/index.rst
index dc69ba0b05e4..4f6c1a695fa9 100644
--- a/Documentation/admin-guide/hw-vuln/index.rst
+++ b/Documentation/admin-guide/hw-vuln/index.rst
@@ -23,3 +23,4 @@ are configurable at compile, boot or run time.
srso
reg-file-data-sampling
indirect-target-selection
+ vmscape
diff --git a/Documentation/admin-guide/hw-vuln/vmscape.rst b/Documentation/admin-guide/hw-vuln/vmscape.rst
new file mode 100644
index 000000000000..d9b9a2b6c114
--- /dev/null
+++ b/Documentation/admin-guide/hw-vuln/vmscape.rst
@@ -0,0 +1,110 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+VMSCAPE
+=======
+
+VMSCAPE is a vulnerability that may allow a guest to influence the branch
+prediction in host userspace. It particularly affects hypervisors like QEMU.
+
+Even if a hypervisor may not have any sensitive data like disk encryption keys,
+guest-userspace may be able to attack the guest-kernel using the hypervisor as
+a confused deputy.
+
+Affected processors
+-------------------
+
+The following CPU families are affected by VMSCAPE:
+
+**Intel processors:**
+ - Skylake generation (Parts without Enhanced-IBRS)
+ - Cascade Lake generation - (Parts affected by ITS guest/host separation)
+ - Alder Lake and newer (Parts affected by BHI)
+
+Note that, BHI affected parts that use BHB clearing software mitigation e.g.
+Icelake are not vulnerable to VMSCAPE.
+
+**AMD processors:**
+ - Zen series (families 0x17, 0x19, 0x1a)
+
+** Hygon processors:**
+ - Family 0x18
+
+Mitigation
+----------
+
+Conditional IBPB
+----------------
+
+Kernel tracks when a CPU has run a potentially malicious guest and issues an
+IBPB before the first exit to userspace after VM-exit. If userspace did not run
+between VM-exit and the next VM-entry, no IBPB is issued.
+
+Note that the existing userspace mitigation against Spectre-v2 is effective in
+protecting the userspace. They are insufficient to protect the userspace VMMs
+from a malicious guest. This is because Spectre-v2 mitigations are applied at
+context switch time, while the userspace VMM can run after a VM-exit without a
+context switch.
+
+Vulnerability enumeration and mitigation is not applied inside a guest. This is
+because nested hypervisors should already be deploying IBPB to isolate
+themselves from nested guests.
+
+SMT considerations
+------------------
+
+When Simultaneous Multi-Threading (SMT) is enabled, hypervisors can be
+vulnerable to cross-thread attacks. For complete protection against VMSCAPE
+attacks in SMT environments, STIBP should be enabled.
+
+The kernel will issue a warning if SMT is enabled without adequate STIBP
+protection. Warning is not issued when:
+
+- SMT is disabled
+- STIBP is enabled system-wide
+- Intel eIBRS is enabled (which implies STIBP protection)
+
+System information and options
+------------------------------
+
+The sysfs file showing VMSCAPE mitigation status is:
+
+ /sys/devices/system/cpu/vulnerabilities/vmscape
+
+The possible values in this file are:
+
+ * 'Not affected':
+
+ The processor is not vulnerable to VMSCAPE attacks.
+
+ * 'Vulnerable':
+
+ The processor is vulnerable and no mitigation has been applied.
+
+ * 'Mitigation: IBPB before exit to userspace':
+
+ Conditional IBPB mitigation is enabled. The kernel tracks when a CPU has
+ run a potentially malicious guest and issues an IBPB before the first
+ exit to userspace after VM-exit.
+
+ * 'Mitigation: IBPB on VMEXIT':
+
+ IBPB is issued on every VM-exit. This occurs when other mitigations like
+ RETBLEED or SRSO are already issuing IBPB on VM-exit.
+
+Mitigation control on the kernel command line
+----------------------------------------------
+
+The mitigation can be controlled via the ``vmscape=`` command line parameter:
+
+ * ``vmscape=off``:
+
+ Disable the VMSCAPE mitigation.
+
+ * ``vmscape=ibpb``:
+
+ Enable conditional IBPB mitigation (default when CONFIG_MITIGATION_VMSCAPE=y).
+
+ * ``vmscape=force``:
+
+ Force vulnerability detection and mitigation even on processors that are
+ not known to be affected.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f12ba5c12b91..25e07ac5c1ca 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3107,6 +3107,7 @@
ssbd=force-off [ARM64]
nospectre_bhb [ARM64]
tsx_async_abort=off [X86]
+ vmscape=off [X86]
Exceptions:
This does not have any effect on
@@ -6399,6 +6400,16 @@
vmpoff= [KNL,S390] Perform z/VM CP command after power off.
Format: <command>
+ vmscape= [X86] Controls mitigation for VMscape attacks.
+ VMscape attacks can leak information from a userspace
+ hypervisor to a guest via speculative side-channels.
+
+ off - disable the mitigation
+ ibpb - use Indirect Branch Prediction Barrier
+ (IBPB) mitigation (default)
+ force - force vulnerability detection even on
+ unaffected processors
+
vsyscall= [X86-64]
Controls the behavior of vsyscalls (i.e. calls to
fixed addresses of 0xffffffffff600x00 from legacy
diff --git a/Makefile b/Makefile
index 1d707d015784..bc6478fae988 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
VERSION = 5
PATCHLEVEL = 15
-SUBLEVEL = 192
+SUBLEVEL = 193
EXTRAVERSION =
NAME = Trick or Treat
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3b9ba4b227d5..68a7a1d989f9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2537,6 +2537,15 @@ config MITIGATION_TSA
security vulnerability on AMD CPUs which can lead to forwarding of
invalid info to subsequent instructions and thus can affect their
timing and thereby cause a leakage.
+
+config MITIGATION_VMSCAPE
+ bool "Mitigate VMSCAPE"
+ depends on KVM
+ default y
+ help
+ Enable mitigation for VMSCAPE attacks. VMSCAPE is a hardware security
+ vulnerability on Intel and AMD CPUs that may allow a guest to do
+ Spectre v2 style attacks on userspace hypervisor.
endif
config ARCH_HAS_ADD_PAGES
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index b8d945d8d34f..9fe8a408f182 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -439,6 +439,7 @@
#define X86_FEATURE_TSA_SQ_NO (21*32+11) /* "" AMD CPU not vulnerable to TSA-SQ */
#define X86_FEATURE_TSA_L1_NO (21*32+12) /* "" AMD CPU not vulnerable to TSA-L1 */
#define X86_FEATURE_CLEAR_CPU_BUF_VM (21*32+13) /* "" Clear CPU buffers using VERW before VMRUN */
+#define X86_FEATURE_IBPB_EXIT_TO_USER (21*32+14) /* Use IBPB on exit-to-userspace, see VMSCAPE bug */
/*
* BUG word(s)
@@ -492,4 +493,5 @@
#define X86_BUG_ITS X86_BUG(1*32 + 5) /* CPU is affected by Indirect Target Selection */
#define X86_BUG_ITS_NATIVE_ONLY X86_BUG(1*32 + 6) /* CPU is affected by ITS, VMX is not affected */
#define X86_BUG_TSA X86_BUG(1*32+ 9) /* "tsa" CPU is affected by Transient Scheduler Attacks */
+#define X86_BUG_VMSCAPE X86_BUG(1*32+10) /* "vmscape" CPU is affected by VMSCAPE attacks from guests */
#endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h
index f27d6cecd803..4ab6de4682de 100644
--- a/arch/x86/include/asm/entry-common.h
+++ b/arch/x86/include/asm/entry-common.h
@@ -86,6 +86,13 @@ static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
* 6 (ia32) bits.
*/
choose_random_kstack_offset(rdtsc() & 0xFF);
+
+ /* Avoid unnecessary reads of 'x86_ibpb_exit_to_user' */
+ if (cpu_feature_enabled(X86_FEATURE_IBPB_EXIT_TO_USER) &&
+ this_cpu_read(x86_ibpb_exit_to_user)) {
+ indirect_branch_prediction_barrier();
+ this_cpu_write(x86_ibpb_exit_to_user, false);
+ }
}
#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index b62ce153a3c4..0a366da54087 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -396,6 +396,8 @@ void alternative_msr_write(unsigned int msr, u64 val, unsigned int feature)
extern u64 x86_pred_cmd;
+DECLARE_PER_CPU(bool, x86_ibpb_exit_to_user);
+
static inline void indirect_branch_prediction_barrier(void)
{
alternative_msr_write(MSR_IA32_PRED_CMD, x86_pred_cmd, X86_FEATURE_USE_IBPB);
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9e313ee9ba66..1628c0014589 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -50,6 +50,7 @@ static void __init gds_select_mitigation(void);
static void __init srso_select_mitigation(void);
static void __init its_select_mitigation(void);
static void __init tsa_select_mitigation(void);
+static void __init vmscape_select_mitigation(void);
/* The base value of the SPEC_CTRL MSR without task-specific bits set */
u64 x86_spec_ctrl_base;
@@ -59,6 +60,14 @@ EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);
DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
EXPORT_SYMBOL_GPL(x86_spec_ctrl_current);
+/*
+ * Set when the CPU has run a potentially malicious guest. An IBPB will
+ * be needed to before running userspace. That IBPB will flush the branch
+ * predictor content.
+ */
+DEFINE_PER_CPU(bool, x86_ibpb_exit_to_user);
+EXPORT_PER_CPU_SYMBOL_GPL(x86_ibpb_exit_to_user);
+
u64 x86_pred_cmd __ro_after_init = PRED_CMD_IBPB;
EXPORT_SYMBOL_GPL(x86_pred_cmd);
@@ -185,6 +194,7 @@ void __init cpu_select_mitigations(void)
gds_select_mitigation();
its_select_mitigation();
tsa_select_mitigation();
+ vmscape_select_mitigation();
}
/*
@@ -2036,10 +2046,6 @@ static void update_mds_branch_idle(void)
}
}
-#define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
-#define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n"
-#define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n"
-
#undef pr_fmt
#define pr_fmt(fmt) "Transient Scheduler Attacks: " fmt
@@ -2128,80 +2134,6 @@ static void __init tsa_select_mitigation(void)
pr_info("%s\n", tsa_strings[tsa_mitigation]);
}
-void cpu_bugs_smt_update(void)
-{
- mutex_lock(&spec_ctrl_mutex);
-
- if (sched_smt_active() && unprivileged_ebpf_enabled() &&
- spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
- pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
-
- switch (spectre_v2_user_stibp) {
- case SPECTRE_V2_USER_NONE:
- break;
- case SPECTRE_V2_USER_STRICT:
- case SPECTRE_V2_USER_STRICT_PREFERRED:
- update_stibp_strict();
- break;
- case SPECTRE_V2_USER_PRCTL:
- case SPECTRE_V2_USER_SECCOMP:
- update_indir_branch_cond();
- break;
- }
-
- switch (mds_mitigation) {
- case MDS_MITIGATION_FULL:
- case MDS_MITIGATION_VMWERV:
- if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY))
- pr_warn_once(MDS_MSG_SMT);
- update_mds_branch_idle();
- break;
- case MDS_MITIGATION_OFF:
- break;
- }
-
- switch (taa_mitigation) {
- case TAA_MITIGATION_VERW:
- case TAA_MITIGATION_UCODE_NEEDED:
- if (sched_smt_active())
- pr_warn_once(TAA_MSG_SMT);
- break;
- case TAA_MITIGATION_TSX_DISABLED:
- case TAA_MITIGATION_OFF:
- break;
- }
-
- switch (mmio_mitigation) {
- case MMIO_MITIGATION_VERW:
- case MMIO_MITIGATION_UCODE_NEEDED:
- if (sched_smt_active())
- pr_warn_once(MMIO_MSG_SMT);
- break;
- case MMIO_MITIGATION_OFF:
- break;
- }
-
- switch (tsa_mitigation) {
- case TSA_MITIGATION_USER_KERNEL:
- case TSA_MITIGATION_VM:
- case TSA_MITIGATION_FULL:
- case TSA_MITIGATION_UCODE_NEEDED:
- /*
- * TSA-SQ can potentially lead to info leakage between
- * SMT threads.
- */
- if (sched_smt_active())
- static_branch_enable(&cpu_buf_idle_clear);
- else
- static_branch_disable(&cpu_buf_idle_clear);
- break;
- case TSA_MITIGATION_NONE:
- break;
- }
-
- mutex_unlock(&spec_ctrl_mutex);
-}
-
#undef pr_fmt
#define pr_fmt(fmt) "Speculative Store Bypass: " fmt
@@ -2890,9 +2822,172 @@ static void __init srso_select_mitigation(void)
x86_pred_cmd = PRED_CMD_SBPB;
}
+#undef pr_fmt
+#define pr_fmt(fmt) "VMSCAPE: " fmt
+
+enum vmscape_mitigations {
+ VMSCAPE_MITIGATION_NONE,
+ VMSCAPE_MITIGATION_AUTO,
+ VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER,
+ VMSCAPE_MITIGATION_IBPB_ON_VMEXIT,
+};
+
+static const char * const vmscape_strings[] = {
+ [VMSCAPE_MITIGATION_NONE] = "Vulnerable",
+ /* [VMSCAPE_MITIGATION_AUTO] */
+ [VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER] = "Mitigation: IBPB before exit to userspace",
+ [VMSCAPE_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT",
+};
+
+static enum vmscape_mitigations vmscape_mitigation __ro_after_init =
+ IS_ENABLED(CONFIG_MITIGATION_VMSCAPE) ? VMSCAPE_MITIGATION_AUTO : VMSCAPE_MITIGATION_NONE;
+
+static int __init vmscape_parse_cmdline(char *str)
+{
+ if (!str)
+ return -EINVAL;
+
+ if (!strcmp(str, "off")) {
+ vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
+ } else if (!strcmp(str, "ibpb")) {
+ vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER;
+ } else if (!strcmp(str, "force")) {
+ setup_force_cpu_bug(X86_BUG_VMSCAPE);
+ vmscape_mitigation = VMSCAPE_MITIGATION_AUTO;
+ } else {
+ pr_err("Ignoring unknown vmscape=%s option.\n", str);
+ }
+
+ return 0;
+}
+early_param("vmscape", vmscape_parse_cmdline);
+
+static void __init vmscape_select_mitigation(void)
+{
+ if (cpu_mitigations_off() ||
+ !boot_cpu_has_bug(X86_BUG_VMSCAPE) ||
+ !boot_cpu_has(X86_FEATURE_IBPB)) {
+ vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
+ return;
+ }
+
+ if (vmscape_mitigation == VMSCAPE_MITIGATION_AUTO)
+ vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER;
+
+ if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB ||
+ srso_mitigation == SRSO_MITIGATION_IBPB_ON_VMEXIT)
+ vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_ON_VMEXIT;
+
+ if (vmscape_mitigation == VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER)
+ setup_force_cpu_cap(X86_FEATURE_IBPB_EXIT_TO_USER);
+
+ pr_info("%s\n", vmscape_strings[vmscape_mitigation]);
+}
+
#undef pr_fmt
#define pr_fmt(fmt) fmt
+#define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
+#define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n"
+#define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n"
+#define VMSCAPE_MSG_SMT "VMSCAPE: SMT on, STIBP is required for full protection. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/vmscape.html for more details.\n"
+
+void cpu_bugs_smt_update(void)
+{
+ mutex_lock(&spec_ctrl_mutex);
+
+ if (sched_smt_active() && unprivileged_ebpf_enabled() &&
+ spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
+ pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
+
+ switch (spectre_v2_user_stibp) {
+ case SPECTRE_V2_USER_NONE:
+ break;
+ case SPECTRE_V2_USER_STRICT:
+ case SPECTRE_V2_USER_STRICT_PREFERRED:
+ update_stibp_strict();
+ break;
+ case SPECTRE_V2_USER_PRCTL:
+ case SPECTRE_V2_USER_SECCOMP:
+ update_indir_branch_cond();
+ break;
+ }
+
+ switch (mds_mitigation) {
+ case MDS_MITIGATION_FULL:
+ case MDS_MITIGATION_VMWERV:
+ if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY))
+ pr_warn_once(MDS_MSG_SMT);
+ update_mds_branch_idle();
+ break;
+ case MDS_MITIGATION_OFF:
+ break;
+ }
+
+ switch (taa_mitigation) {
+ case TAA_MITIGATION_VERW:
+ case TAA_MITIGATION_UCODE_NEEDED:
+ if (sched_smt_active())
+ pr_warn_once(TAA_MSG_SMT);
+ break;
+ case TAA_MITIGATION_TSX_DISABLED:
+ case TAA_MITIGATION_OFF:
+ break;
+ }
+
+ switch (mmio_mitigation) {
+ case MMIO_MITIGATION_VERW:
+ case MMIO_MITIGATION_UCODE_NEEDED:
+ if (sched_smt_active())
+ pr_warn_once(MMIO_MSG_SMT);
+ break;
+ case MMIO_MITIGATION_OFF:
+ break;
+ }
+
+ switch (tsa_mitigation) {
+ case TSA_MITIGATION_USER_KERNEL:
+ case TSA_MITIGATION_VM:
+ case TSA_MITIGATION_FULL:
+ case TSA_MITIGATION_UCODE_NEEDED:
+ /*
+ * TSA-SQ can potentially lead to info leakage between
+ * SMT threads.
+ */
+ if (sched_smt_active())
+ static_branch_enable(&cpu_buf_idle_clear);
+ else
+ static_branch_disable(&cpu_buf_idle_clear);
+ break;
+ case TSA_MITIGATION_NONE:
+ break;
+ }
+
+ switch (vmscape_mitigation) {
+ case VMSCAPE_MITIGATION_NONE:
+ case VMSCAPE_MITIGATION_AUTO:
+ break;
+ case VMSCAPE_MITIGATION_IBPB_ON_VMEXIT:
+ case VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER:
+ /*
+ * Hypervisors can be attacked across-threads, warn for SMT when
+ * STIBP is not already enabled system-wide.
+ *
+ * Intel eIBRS (!AUTOIBRS) implies STIBP on.
+ */
+ if (!sched_smt_active() ||
+ spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT ||
+ spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED ||
+ (spectre_v2_in_eibrs_mode(spectre_v2_enabled) &&
+ !boot_cpu_has(X86_FEATURE_AUTOIBRS)))
+ break;
+ pr_warn_once(VMSCAPE_MSG_SMT);
+ break;
+ }
+
+ mutex_unlock(&spec_ctrl_mutex);
+}
+
#ifdef CONFIG_SYSFS
#define L1TF_DEFAULT_MSG "Mitigation: PTE Inversion"
@@ -3138,6 +3233,11 @@ static ssize_t tsa_show_state(char *buf)
return sysfs_emit(buf, "%s\n", tsa_strings[tsa_mitigation]);
}
+static ssize_t vmscape_show_state(char *buf)
+{
+ return sysfs_emit(buf, "%s\n", vmscape_strings[vmscape_mitigation]);
+}
+
static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
char *buf, unsigned int bug)
{
@@ -3202,6 +3302,9 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
case X86_BUG_TSA:
return tsa_show_state(buf);
+ case X86_BUG_VMSCAPE:
+ return vmscape_show_state(buf);
+
default:
break;
}
@@ -3291,4 +3394,9 @@ ssize_t cpu_show_tsa(struct device *dev, struct device_attribute *attr, char *bu
{
return cpu_show_common(dev, attr, buf, X86_BUG_TSA);
}
+
+ssize_t cpu_show_vmscape(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ return cpu_show_common(dev, attr, buf, X86_BUG_VMSCAPE);
+}
#endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index b16a77386236..96643de567d8 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1148,42 +1148,51 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
#define ITS_NATIVE_ONLY BIT(9)
/* CPU is affected by Transient Scheduler Attacks */
#define TSA BIT(10)
+/* CPU is affected by VMSCAPE */
+#define VMSCAPE BIT(11)
static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
- VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS),
- VULNBL_INTEL_STEPPINGS(HASWELL, X86_STEPPING_ANY, SRBDS),
- VULNBL_INTEL_STEPPINGS(HASWELL_L, X86_STEPPING_ANY, SRBDS),
- VULNBL_INTEL_STEPPINGS(HASWELL_G, X86_STEPPING_ANY, SRBDS),
- VULNBL_INTEL_STEPPINGS(HASWELL_X, X86_STEPPING_ANY, MMIO),
- VULNBL_INTEL_STEPPINGS(BROADWELL_D, X86_STEPPING_ANY, MMIO),
- VULNBL_INTEL_STEPPINGS(BROADWELL_G, X86_STEPPING_ANY, SRBDS),
- VULNBL_INTEL_STEPPINGS(BROADWELL_X, X86_STEPPING_ANY, MMIO),
- VULNBL_INTEL_STEPPINGS(BROADWELL, X86_STEPPING_ANY, SRBDS),
- VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPINGS(0x0, 0x5), MMIO | RETBLEED | GDS),
- VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | ITS),
- VULNBL_INTEL_STEPPINGS(SKYLAKE_L, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS),
- VULNBL_INTEL_STEPPINGS(SKYLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS),
- VULNBL_INTEL_STEPPINGS(KABYLAKE_L, X86_STEPPINGS(0x0, 0xb), MMIO | RETBLEED | GDS | SRBDS),
- VULNBL_INTEL_STEPPINGS(KABYLAKE_L, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | ITS),
- VULNBL_INTEL_STEPPINGS(KABYLAKE, X86_STEPPINGS(0x0, 0xc), MMIO | RETBLEED | GDS | SRBDS),
- VULNBL_INTEL_STEPPINGS(KABYLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | ITS),
- VULNBL_INTEL_STEPPINGS(CANNONLAKE_L, X86_STEPPING_ANY, RETBLEED),
+ VULNBL_INTEL_STEPPINGS(SANDYBRIDGE_X, X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SANDYBRIDGE, X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(IVYBRIDGE_X, X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(HASWELL, X86_STEPPING_ANY, SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(HASWELL_L, X86_STEPPING_ANY, SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(HASWELL_G, X86_STEPPING_ANY, SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(HASWELL_X, X86_STEPPING_ANY, MMIO | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(BROADWELL_D, X86_STEPPING_ANY, MMIO | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(BROADWELL_X, X86_STEPPING_ANY, MMIO | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(BROADWELL_G, X86_STEPPING_ANY, SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(BROADWELL, X86_STEPPING_ANY, SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPINGS(0x0, 0x5), MMIO | RETBLEED | GDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE_X, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE_L, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SKYLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE_L, X86_STEPPINGS(0x0, 0xb), MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE_L, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE, X86_STEPPINGS(0x0, 0xc), MMIO | RETBLEED | GDS | SRBDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(KABYLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | SRBDS | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(CANNONLAKE_L, X86_STEPPING_ANY, RETBLEED | VMSCAPE),
VULNBL_INTEL_STEPPINGS(ICELAKE_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | ITS_NATIVE_ONLY),
VULNBL_INTEL_STEPPINGS(ICELAKE_D, X86_STEPPING_ANY, MMIO | GDS | ITS | ITS_NATIVE_ONLY),
VULNBL_INTEL_STEPPINGS(ICELAKE_X, X86_STEPPING_ANY, MMIO | GDS | ITS | ITS_NATIVE_ONLY),
- VULNBL_INTEL_STEPPINGS(COMETLAKE, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
- VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPINGS(0x0, 0x0), MMIO | RETBLEED | ITS),
- VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS),
+ VULNBL_INTEL_STEPPINGS(COMETLAKE, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPINGS(0x0, 0x0), MMIO | RETBLEED | ITS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(COMETLAKE_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED | GDS | ITS | VMSCAPE),
VULNBL_INTEL_STEPPINGS(TIGERLAKE_L, X86_STEPPING_ANY, GDS | ITS | ITS_NATIVE_ONLY),
VULNBL_INTEL_STEPPINGS(TIGERLAKE, X86_STEPPING_ANY, GDS | ITS | ITS_NATIVE_ONLY),
VULNBL_INTEL_STEPPINGS(LAKEFIELD, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED),
VULNBL_INTEL_STEPPINGS(ROCKETLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS | ITS | ITS_NATIVE_ONLY),
- VULNBL_INTEL_STEPPINGS(ALDERLAKE, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(ALDERLAKE_L, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(RAPTORLAKE, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(RAPTORLAKE_P, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(RAPTORLAKE_S, X86_STEPPING_ANY, RFDS),
- VULNBL_INTEL_STEPPINGS(ALDERLAKE_N, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE_L, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE_N, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE_P, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE_S, X86_STEPPING_ANY, RFDS | VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(LUNARLAKE_M, X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(SAPPHIRERAPIDS_X,X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(GRANITERAPIDS_X, X86_STEPPING_ANY, VMSCAPE),
+ VULNBL_INTEL_STEPPINGS(EMERALDRAPIDS_X, X86_STEPPING_ANY, VMSCAPE),
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RFDS),
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_D, X86_STEPPING_ANY, MMIO | RFDS),
VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RFDS),
@@ -1193,9 +1202,9 @@ static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_AMD(0x15, RETBLEED),
VULNBL_AMD(0x16, RETBLEED),
- VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO),
- VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO),
- VULNBL_AMD(0x19, SRSO | TSA),
+ VULNBL_AMD(0x17, RETBLEED | SMT_RSB | SRSO | VMSCAPE),
+ VULNBL_HYGON(0x18, RETBLEED | SMT_RSB | SRSO | VMSCAPE),
+ VULNBL_AMD(0x19, SRSO | TSA | VMSCAPE),
{}
};
@@ -1410,6 +1419,14 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
}
}
+ /*
+ * Set the bug only on bare-metal. A nested hypervisor should already be
+ * deploying IBPB to isolate itself from nested guests.
+ */
+ if (cpu_matches(cpu_vuln_blacklist, VMSCAPE) &&
+ !boot_cpu_has(X86_FEATURE_HYPERVISOR))
+ setup_force_cpu_bug(X86_BUG_VMSCAPE);
+
if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
return;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 52c59c3bcb91..2ba297da7bde 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10023,6 +10023,15 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
static_call(kvm_x86_handle_exit_irqoff)(vcpu);
+ /*
+ * Mark this CPU as needing a branch predictor flush before running
+ * userspace. Must be done before enabling preemption to ensure it gets
+ * set for the CPU that actually ran the guest, and not the CPU that it
+ * may migrate to.
+ */
+ if (cpu_feature_enabled(X86_FEATURE_IBPB_EXIT_TO_USER))
+ this_cpu_write(x86_ibpb_exit_to_user, true);
+
/*
* Consume any pending interrupts, including the possible source of
* VM-Exit on SVM and any ticks that occur between VM-Exit and now.
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 0e7f7f54665d..64d270ba759f 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -605,6 +605,10 @@ ssize_t __weak cpu_show_tsa(struct device *dev, struct device_attribute *attr, c
{
return sysfs_emit(buf, "Not affected\n");
}
+ssize_t __weak cpu_show_vmscape(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "Not affected\n");
+}
static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
@@ -622,6 +626,7 @@ static DEVICE_ATTR(spec_rstack_overflow, 0444, cpu_show_spec_rstack_overflow, NU
static DEVICE_ATTR(reg_file_data_sampling, 0444, cpu_show_reg_file_data_sampling, NULL);
static DEVICE_ATTR(indirect_target_selection, 0444, cpu_show_indirect_target_selection, NULL);
static DEVICE_ATTR(tsa, 0444, cpu_show_tsa, NULL);
+static DEVICE_ATTR(vmscape, 0444, cpu_show_vmscape, NULL);
static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_meltdown.attr,
@@ -640,6 +645,7 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_reg_file_data_sampling.attr,
&dev_attr_indirect_target_selection.attr,
&dev_attr_tsa.attr,
+ &dev_attr_vmscape.attr,
NULL
};
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index ab1b88b16982..5640c3617a7b 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -79,6 +79,7 @@ extern ssize_t cpu_show_reg_file_data_sampling(struct device *dev,
extern ssize_t cpu_show_indirect_target_selection(struct device *dev,
struct device_attribute *attr, char *buf);
extern ssize_t cpu_show_tsa(struct device *dev, struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_vmscape(struct device *dev, struct device_attribute *attr, char *buf);
extern __printf(4, 5)
struct device *cpu_device_create(struct device *parent, void *drvdata,
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