Re: [PATCH v7 03/15] KVM: x86: Add Arch LBR MSRs to msrs_to_save_all list

From: Like Xu
Date: Mon Aug 09 2021 - 09:07:14 EST


On 6/8/2021 3:42 pm, Yang Weijiang wrote:
Arch LBR MSR_ARCH_LBR_DEPTH and MSR_ARCH_LBR_CTL are {saved|restored}
by userspace application if they're available.

Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4116567f3d44..4ae173ab2208 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1327,6 +1327,7 @@ static const u32 msrs_to_save_all[] = {
MSR_ARCH_PERFMON_EVENTSEL0 + 12, MSR_ARCH_PERFMON_EVENTSEL0 + 13,
MSR_ARCH_PERFMON_EVENTSEL0 + 14, MSR_ARCH_PERFMON_EVENTSEL0 + 15,
MSR_ARCH_PERFMON_EVENTSEL0 + 16, MSR_ARCH_PERFMON_EVENTSEL0 + 17,
+ MSR_ARCH_LBR_CTL, MSR_ARCH_LBR_DEPTH,

Hi Jim,

Do you have a particular reason for not putting the set of
MSR_ARCH_LBR_{FROM, TO, INFO} into msrs_to_save_all[]
for {saved|restored} by user space ?

};
static u32 msrs_to_save[ARRAY_SIZE(msrs_to_save_all)];
@@ -6229,6 +6230,11 @@ static void kvm_init_msr_list(void)
min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp))
continue;
break;
+ case MSR_ARCH_LBR_DEPTH:
+ case MSR_ARCH_LBR_CTL:
+ if (!kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR))
+ continue;
+ break;
default:
break;
}