x86/cpu: Reinitialize IA32_FEAT_CTL MSR on BSP during wakeup

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.

Fixes: 21bd346 ("KVM: VMX: Drop initialization of IA32_FEAT_CTL MSR")
Reported-by: Brad Campbell <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Liam Merwick <[email protected]>
Reviewed-by: Maxim Levitsky <[email protected]>
Tested-by: Brad Campbell <[email protected]>
Cc: [email protected] # v5.6
Link: https://lkml.kernel.org/r/[email protected]

Author: Sean Christopherson

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 */

arch/x86/kernel/cpu/centaur.c

@@ -3,6 +3,7 @@
 #include <linux/sched.h>
 #include <linux/sched/clock.h>
 
+#include <asm/cpu.h>
 #include <asm/cpufeature.h>
 #include <asm/e820/api.h>
 #include <asm/mtrr.h>

arch/x86/kernel/cpu/cpu.h

@@ -81,8 +81,4 @@ extern void update_srbds_msr(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 */

arch/x86/kernel/cpu/zhaoxin.c

@@ -2,6 +2,7 @@
 #include <linux/sched.h>
 #include <linux/sched/clock.h>
 
+#include <asm/cpu.h>
 #include <asm/cpufeature.h>
 
 #include "cpu.h"

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 */