linux-kernel - [tip: x86/urgent] x86/pm: Add enumeration check before spec MSRs save/restore setup

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Message-ID: <166903694145.4906.11522120467874564275.tip-bot2@tip-bot2>
Date:   Mon, 21 Nov 2022 13:22:21 -0000
From:   "tip-bot2 for Pawan Gupta" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Borislav Petkov <bp@...e.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        <stable@...nel.org>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/pm: Add enumeration check before spec MSRs
 save/restore setup

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     50bcceb7724e471d9b591803889df45dcbb584bc
Gitweb:        https://git.kernel.org/tip/50bcceb7724e471d9b591803889df45dcbb584bc
Author:        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
AuthorDate:    Tue, 15 Nov 2022 11:17:06 -08:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Mon, 21 Nov 2022 14:16:16 +01:00

x86/pm: Add enumeration check before spec MSRs save/restore setup

pm_save_spec_msr() keeps a list of all the MSRs which _might_ need
to be saved and restored at hibernate and resume. However, it has
zero awareness of CPU support for these MSRs. It mostly works by
unconditionally attempting to manipulate these MSRs and relying on
rdmsrl_safe() being able to handle a #GP on CPUs where the support is
unavailable.

However, it's possible for reads (RDMSR) to be supported for a given MSR
while writes (WRMSR) are not. In this case, msr_build_context() sees
a successful read (RDMSR) and marks the MSR as valid. Then, later, a
write (WRMSR) fails, producing a nasty (but harmless) error message.
This causes restore_processor_state() to try and restore it, but writing
this MSR is not allowed on the Intel Atom N2600 leading to:

  unchecked MSR access error: WRMSR to 0x122 (tried to write 0x0000000000000002) \
     at rIP: 0xffffffff8b07a574 (native_write_msr+0x4/0x20)
  Call Trace:
   <TASK>
   restore_processor_state
   x86_acpi_suspend_lowlevel
   acpi_suspend_enter
   suspend_devices_and_enter
   pm_suspend.cold
   state_store
   kernfs_fop_write_iter
   vfs_write
   ksys_write
   do_syscall_64
   ? do_syscall_64
   ? up_read
   ? lock_is_held_type
   ? asm_exc_page_fault
   ? lockdep_hardirqs_on
   entry_SYSCALL_64_after_hwframe

To fix this, add the corresponding X86_FEATURE bit for each MSR.  Avoid
trying to manipulate the MSR when the feature bit is clear. This
required adding a X86_FEATURE bit for MSRs that do not have one already,
but it's a small price to pay.

  [ bp: Move struct msr_enumeration inside the only function that uses it. ]

Fixes: 73924ec4d560 ("x86/pm: Save the MSR validity status at context setup")
Reported-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: <stable@...nel.org>
Link: https://lore.kernel.org/r/c24db75d69df6e66c0465e13676ad3f2837a2ed8.1668539735.git.pawan.kumar.gupta@linux.intel.com
---
 arch/x86/power/cpu.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 4cd39f3..93ae332 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -513,16 +513,23 @@ static int pm_cpu_check(const struct x86_cpu_id *c)
 
 static void pm_save_spec_msr(void)
 {
-	u32 spec_msr_id[] = {
-		MSR_IA32_SPEC_CTRL,
-		MSR_IA32_TSX_CTRL,
-		MSR_TSX_FORCE_ABORT,
-		MSR_IA32_MCU_OPT_CTRL,
-		MSR_AMD64_LS_CFG,
-		MSR_AMD64_DE_CFG,
+	struct msr_enumeration {
+		u32 msr_no;
+		u32 feature;
+	} msr_enum[] = {
+		{ MSR_IA32_SPEC_CTRL,	 X86_FEATURE_MSR_SPEC_CTRL },
+		{ MSR_IA32_TSX_CTRL,	 X86_FEATURE_MSR_TSX_CTRL },
+		{ MSR_TSX_FORCE_ABORT,	 X86_FEATURE_TSX_FORCE_ABORT },
+		{ MSR_IA32_MCU_OPT_CTRL, X86_FEATURE_SRBDS_CTRL },
+		{ MSR_AMD64_LS_CFG,	 X86_FEATURE_LS_CFG_SSBD },
+		{ MSR_AMD64_DE_CFG,	 X86_FEATURE_LFENCE_RDTSC },
 	};
+	int i;
 
-	msr_build_context(spec_msr_id, ARRAY_SIZE(spec_msr_id));
+	for (i = 0; i < ARRAY_SIZE(msr_enum); i++) {
+		if (boot_cpu_has(msr_enum[i].feature))
+			msr_build_context(&msr_enum[i].msr_no, 1);
+	}
 }
 
 static int pm_check_save_msr(void)