lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20230306163425.8324-6-jgross@suse.com>
Date:   Mon,  6 Mar 2023 17:34:18 +0100
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, xen-devel@...ts.xenproject.org
Subject: [PATCH v4 05/12] x86/xen: set MTRR state when running as Xen PV initial domain

When running as Xen PV initial domain (aka dom0), MTRRs are disabled
by the hypervisor, but the system should nevertheless use correct
cache memory types. This has always kind of worked, as disabled MTRRs
resulted in disabled PAT, too, so that the kernel avoided code paths
resulting in inconsistencies. This bypassed all of the sanity checks
the kernel is doing with enabled MTRRs in order to avoid memory
mappings with conflicting memory types.

This has been changed recently, leading to PAT being accepted to be
enabled, while MTRRs stayed disabled. The result is that
mtrr_type_lookup() no longer is accepting all memory type requests,
but started to return WB even if UC- was requested. This led to
driver failures during initialization of some devices.

In reality MTRRs are still in effect, but they are under complete
control of the Xen hypervisor. It is possible, however, to retrieve
the MTRR settings from the hypervisor.

In order to fix those problems, overwrite the MTRR state via
mtrr_overwrite_state() with the MTRR data from the hypervisor, if the
system is running as a Xen dom0.

Fixes: 72cbc8f04fe2 ("x86/PAT: Have pat_enabled() properly reflect state when running on Xen")
Signed-off-by: Juergen Gross <jgross@...e.com>
---
V2:
- new patch
V3:
- move the call of mtrr_overwrite_state() to xen_pv_init_platform()
V4:
- only call mtrr_overwrite_state() if any MTRR got from Xen
  (Boris Ostrovsky)
---
 arch/x86/xen/enlighten_pv.c | 52 +++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index bb59cc6ddb2d..12e6b6845870 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -68,6 +68,7 @@
 #include <asm/reboot.h>
 #include <asm/hypervisor.h>
 #include <asm/mach_traps.h>
+#include <asm/mtrr.h>
 #include <asm/mwait.h>
 #include <asm/pci_x86.h>
 #include <asm/cpu.h>
@@ -119,6 +120,54 @@ static int __init parse_xen_msr_safe(char *str)
 }
 early_param("xen_msr_safe", parse_xen_msr_safe);
 
+/* Get MTRR settings from Xen and put them into mtrr_state. */
+static void __init xen_set_mtrr_data(void)
+{
+#ifdef CONFIG_MTRR
+	struct xen_platform_op op = {
+		.cmd = XENPF_read_memtype,
+		.interface_version = XENPF_INTERFACE_VERSION,
+	};
+	unsigned int reg;
+	unsigned long mask;
+	uint32_t eax, width;
+	static struct mtrr_var_range var[MTRR_MAX_VAR_RANGES] __initdata;
+
+	/* Get physical address width (only 64-bit cpus supported). */
+	width = 36;
+	eax = cpuid_eax(0x80000000);
+	if ((eax >> 16) == 0x8000 && eax >= 0x80000008) {
+		eax = cpuid_eax(0x80000008);
+		width = eax & 0xff;
+	}
+
+	for (reg = 0; reg < MTRR_MAX_VAR_RANGES; reg++) {
+		op.u.read_memtype.reg = reg;
+		if (HYPERVISOR_platform_op(&op))
+			break;
+
+		/*
+		 * Only called in dom0, which has all RAM PFNs mapped at
+		 * RAM MFNs, and all PCI space etc. is identity mapped.
+		 * This means we can treat MFN == PFN regarding MTTR settings.
+		 */
+		var[reg].base_lo = op.u.read_memtype.type;
+		var[reg].base_lo |= op.u.read_memtype.mfn << PAGE_SHIFT;
+		var[reg].base_hi = op.u.read_memtype.mfn >> (32 - PAGE_SHIFT);
+		mask = ~((op.u.read_memtype.nr_mfns << PAGE_SHIFT) - 1);
+		mask &= (1UL << width) - 1;
+		if (mask)
+			mask |= 1 << 11;
+		var[reg].mask_lo = mask;
+		var[reg].mask_hi = mask >> 32;
+	}
+
+	/* Only overwrite MTRR state if any MTRR could be got from Xen. */
+	if (reg)
+		mtrr_overwrite_state(var, reg, MTRR_TYPE_UNCACHABLE);
+#endif
+}
+
 static void __init xen_pv_init_platform(void)
 {
 	/* PV guests can't operate virtio devices without grants. */
@@ -135,6 +184,9 @@ static void __init xen_pv_init_platform(void)
 
 	/* pvclock is in shared info area */
 	xen_init_time_ops();
+
+	if (xen_initial_domain())
+		xen_set_mtrr_data();
 }
 
 static void __init xen_pv_guest_late_init(void)
-- 
2.35.3

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ