[PATCH] x86/cpu: Reinitialize IA32_FEAT_CTL MSR on BSP during wakeup

Sean Christopherson
2020-06-05T20:07:32Z

Reinitialize IA32_FEAT_CTL on the BSP during wakeup to handle the case
where firmware doesn't initialize or save/restore across S3. This fixes
a bug where IA32_FEAT_CTL is left uninitialized and results in VMXON
taking a #GP due to VMX not being fully enabled, i.e. breaks KVM.

Use init_ia32_feat_ctl() to "restore" IA32_FEAT_CTL as it already deals
with the case where the MSR is locked, and because APs already redo
init_ia32_feat_ctl() during suspend by virtue of the SMP boot flow being
used to reinitialize APs upon wakeup. Do the call in the early wakeup
flow to avoid dependencies in the syscore_ops chain, e.g. simply adding
a resume hook is not guaranteed to work, as KVM does VMXON in its own
resume hook, kvm_resume(), when KVM has active guests.

Reported-by: Brad Campbell <lists2009@fnarfbargle.com>
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Fixes: 21bd3467a58e ("KVM: VMX: Drop initialization of IA32_FEAT_CTL MSR")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/cpu.h | 5 +++++
arch/x86/kernel/cpu/cpu.h | 4 ----
arch/x86/power/cpu.c | 6 ++++++
3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index dd17c2da1af5..da78ccbd493b 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -58,4 +58,9 @@ static inline bool handle_guest_split_lock(unsigned long ip)
return false;
}
#endif
+#ifdef CONFIG_IA32_FEAT_CTL
+void init_ia32_feat_ctl(struct cpuinfo_x86 *c);
+#else
+static inline void init_ia32_feat_ctl(struct cpuinfo_x86 *c) {}
+#endif
#endif /* _ASM_X86_CPU_H */
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
index 37fdefd14f28..38ab6e115eac 100644
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -80,8 +80,4 @@ extern void x86_spec_ctrl_setup_ap(void);

extern u64 x86_read_arch_cap_msr(void);

-#ifdef CONFIG_IA32_FEAT_CTL
-void init_ia32_feat_ctl(struct cpuinfo_x86 *c);
-#endif
-
#endif /* ARCH_X86_CPU_H */
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index aaff9ed7ff45..b0d3c5ca6d80 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -193,6 +193,8 @@ static void fix_processor_context(void)
*/
static void notrace __restore_processor_state(struct saved_context *ctxt)
{
+ struct cpuinfo_x86 *c;
+
if (ctxt->misc_enable_saved)
wrmsrl(MSR_IA32_MISC_ENABLE, ctxt->misc_enable);
/*
@@ -263,6 +265,10 @@ static void notrace __restore_processor_state(struct saved_context *ctxt)
mtrr_bp_restore();
perf_restore_debug_store();
msr_restore_context(ctxt);
+
+ c = &cpu_data(smp_processor_id());
+ if (cpu_has(c, X86_FEATURE_MSR_IA32_FEAT_CTL))
+ init_ia32_feat_ctl(c);
}

/* Needed by apm.c */
--
2.26.0