Re: [PATCH v3 4/8] KVM: X86: Split kvm_update_cpuid()

From: Xiaoyao Li
Date: Wed Jul 08 2020 - 09:27:39 EST

On 7/8/2020 8:41 PM, Paolo Bonzini wrote:
On 08/07/20 14:33, Xiaoyao Li wrote:
On 7/8/2020 8:06 PM, Paolo Bonzini wrote:
On 08/07/20 08:50, Xiaoyao Li wrote:
Split the part of updating vcpu model out of kvm_update_cpuid(), and put
it into a new kvm_update_vcpu_model(). So it's more clear that
kvm_update_cpuid() is to update guest CPUID settings, while
kvm_update_vcpu_model() is to update vcpu model (settings) based on the
updated CPUID settings.

Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>

I would prefer to keep the kvm_update_cpuid name for what you called
kvm_update_vcpu_model(), and rename the rest to
kvm_update_cpuid_runtime().

But there is no CPUID being updated in kvm_update_cpuid(), after
kvm_update_cpuid_runtime() is split out. This is confusing, IMO.

Then what about kvm_vcpu_after_set_cpuid()? It's the "model" that is
not clear.

I'm ok with kvm_vcpu_after_set_cpuid().

BTW there is an unknown for me regarding enter_smm(). Currently, it calls kvm_update_cpuid(). I'm not sure which part it really needs, update CPUID or update vcpu state based on CPUID? maybe both?
So in this Patch, after splitting kvm_update_cpuid(), I keep both functions there to ensure no functional change in enter_smm().
So using the name "kvm_vcpu_after_set_cpuid" seems weird in that function.

Thanks,

Paolo

Paolo

---
 arch/x86/kvm/cpuid.c | 38 ++++++++++++++++++++++++--------------
 arch/x86/kvm/cpuid.h | 1 +
 arch/x86/kvm/x86.c | 1 +
 3 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index a825878b7f84..001f5a94880e 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -76,7 +76,6 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
 void kvm_update_cpuid(struct kvm_vcpu *vcpu)
 {
ÂÂÂÂÂ struct kvm_cpuid_entry2 *best;
-ÂÂÂ struct kvm_lapic *apic = vcpu->arch.apic;
 Â best = kvm_find_cpuid_entry(vcpu, 1, 0);
ÂÂÂÂÂ if (best) {
@@ -89,26 +88,14 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
ÂÂÂÂÂ }
 - if (best && apic) {
-ÂÂÂÂÂÂÂ if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
-ÂÂÂÂÂÂÂÂÂÂÂ apic->lapic_timer.timer_mode_mask = 3 << 17;
-ÂÂÂÂÂÂÂ else
-ÂÂÂÂÂÂÂÂÂÂÂ apic->lapic_timer.timer_mode_mask = 1 << 17;
-ÂÂÂ }
-
ÂÂÂÂÂ best = kvm_find_cpuid_entry(vcpu, 7, 0);
ÂÂÂÂÂ if (best && boot_cpu_has(X86_FEATURE_PKU) && best->function ==
0x7)
ÂÂÂÂÂÂÂÂÂ cpuid_entry_change(best, X86_FEATURE_OSPKE,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ kvm_read_cr4_bits(vcpu, X86_CR4_PKE));
 Â best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
-ÂÂÂ if (!best) {
-ÂÂÂÂÂÂÂ vcpu->arch.guest_supported_xcr0 = 0;
-ÂÂÂ } else {
-ÂÂÂÂÂÂÂ vcpu->arch.guest_supported_xcr0 =
-ÂÂÂÂÂÂÂÂÂÂÂ (best->eax | ((u64)best->edx << 32)) & supported_xcr0;
+ÂÂÂ if (best)
ÂÂÂÂÂÂÂÂÂ best->ebx = xstate_required_size(vcpu->arch.xcr0, false);
-ÂÂÂ }
 Â best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
ÂÂÂÂÂ if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
@@ -127,6 +114,27 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vcpu->arch.ia32_misc_enable_msr &
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ MSR_IA32_MISC_ENABLE_MWAIT);
ÂÂÂÂÂ }
+}
+
+void kvm_update_vcpu_model(struct kvm_vcpu *vcpu)
+{
+ÂÂÂ struct kvm_lapic *apic = vcpu->arch.apic;
+ÂÂÂ struct kvm_cpuid_entry2 *best;
+
+ÂÂÂ best = kvm_find_cpuid_entry(vcpu, 1, 0);
+ÂÂÂ if (best && apic) {
+ÂÂÂÂÂÂÂ if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
+ÂÂÂÂÂÂÂÂÂÂÂ apic->lapic_timer.timer_mode_mask = 3 << 17;
+ÂÂÂÂÂÂÂ else
+ÂÂÂÂÂÂÂÂÂÂÂ apic->lapic_timer.timer_mode_mask = 1 << 17;
+ÂÂÂ }
+
+ÂÂÂ best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
+ÂÂÂ if (!best)
+ÂÂÂÂÂÂÂ vcpu->arch.guest_supported_xcr0 = 0;
+ÂÂÂ else
+ÂÂÂÂÂÂÂ vcpu->arch.guest_supported_xcr0 =
+ÂÂÂÂÂÂÂÂÂÂÂ (best->eax | ((u64)best->edx << 32)) & supported_xcr0;
 Â /* Note, maxphyaddr must be updated before tdp_level. */
ÂÂÂÂÂ vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
@@ -218,6 +226,7 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
ÂÂÂÂÂ kvm_apic_set_version(vcpu);
ÂÂÂÂÂ kvm_x86_ops.cpuid_update(vcpu);
ÂÂÂÂÂ kvm_update_cpuid(vcpu);
+ÂÂÂ kvm_update_vcpu_model(vcpu);
 Â kvfree(cpuid_entries);
 out:
@@ -247,6 +256,7 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
ÂÂÂÂÂ kvm_apic_set_version(vcpu);
ÂÂÂÂÂ kvm_x86_ops.cpuid_update(vcpu);
ÂÂÂÂÂ kvm_update_cpuid(vcpu);
+ÂÂÂ kvm_update_vcpu_model(vcpu);
 out:
ÂÂÂÂÂ return r;
 }
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index f136de1debad..45e3643e2fba 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -10,6 +10,7 @@ extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
 void kvm_set_cpu_caps(void);
  void kvm_update_cpuid(struct kvm_vcpu *vcpu);
+void kvm_update_vcpu_model(struct kvm_vcpu *vcpu);
 struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ u32 function, u32 index);
 int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 09ee54f5e385..6f376392e6e6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8184,6 +8184,7 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 #endif
 Â kvm_update_cpuid(vcpu);
+ÂÂÂ kvm_update_vcpu_model(vcpu);
ÂÂÂÂÂ kvm_mmu_reset_context(vcpu);
 }