[Patch 2/6] KVM: VMX: Use wrmsr for switching between guest and host IA32_XSS

Aaron Lewis
2019-10-09T00:41:57Z

Set IA32_XSS for the guest and host during VM Enter and VM Exit
transitions rather than by using the MSR-load areas.

Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
---
arch/x86/kvm/svm.c | 4 ++--
arch/x86/kvm/vmx/vmx.c | 14 ++------------
arch/x86/kvm/x86.c | 25 +++++++++++++++++++++----
arch/x86/kvm/x86.h | 4 ++--
4 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index f8ecb6df5106..e2d7a7738c76 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5628,7 +5628,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
svm->vmcb->save.cr2 = vcpu->arch.cr2;

clgi();
- kvm_load_guest_xcr0(vcpu);
+ kvm_load_guest_xsave_controls(vcpu);

if (lapic_in_kernel(vcpu) &&
vcpu->arch.apic->lapic_timer.timer_advance_ns)
@@ -5778,7 +5778,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
if (unlikely(svm->vmcb->control.exit_code == SVM_EXIT_NMI))
kvm_before_interrupt(&svm->vcpu);

- kvm_put_guest_xcr0(vcpu);
+ kvm_load_host_xsave_controls(vcpu);
stgi();

/* Any pending NMI will happen here */
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 409e9a7323f1..ff5ba28abecb 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -106,8 +106,6 @@ module_param(enable_apicv, bool, S_IRUGO);
static bool __read_mostly nested = 1;
module_param(nested, bool, S_IRUGO);

-static u64 __read_mostly host_xss;
-
bool __read_mostly enable_pml = 1;
module_param_named(pml, enable_pml, bool, S_IRUGO);

@@ -2074,11 +2072,6 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (data != 0)
return 1;
vcpu->arch.ia32_xss = data;
- if (vcpu->arch.ia32_xss != host_xss)
- add_atomic_switch_msr(vmx, MSR_IA32_XSS,
- vcpu->arch.ia32_xss, host_xss, false);
- else
- clear_atomic_switch_msr(vmx, MSR_IA32_XSS);
break;
case MSR_IA32_RTIT_CTL:
if ((pt_mode != PT_MODE_HOST_GUEST) ||
@@ -6540,7 +6533,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
vmx_set_interrupt_shadow(vcpu, 0);

- kvm_load_guest_xcr0(vcpu);
+ kvm_load_guest_xsave_controls(vcpu);

if (static_cpu_has(X86_FEATURE_PKU) &&
kvm_read_cr4_bits(vcpu, X86_CR4_PKE) &&
@@ -6647,7 +6640,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
__write_pkru(vmx->host_pkru);
}

- kvm_put_guest_xcr0(vcpu);
+ kvm_load_host_xsave_controls(vcpu);

vmx->nested.nested_run_pending = 0;
vmx->idt_vectoring_info = 0;
@@ -7599,9 +7592,6 @@ static __init int hardware_setup(void)
WARN_ONCE(host_bndcfgs, "KVM: BNDCFGS in host will be lost");
}

- if (boot_cpu_has(X86_FEATURE_XSAVES))
- rdmsrl(MSR_IA32_XSS, host_xss);
-
if (!cpu_has_vmx_vpid() || !cpu_has_vmx_invvpid() ||
!(cpu_has_vmx_invvpid_single() || cpu_has_vmx_invvpid_global()))
enable_vpid = 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 661e2bf38526..e90e658fd8a9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -176,6 +176,8 @@ struct kvm_shared_msrs {
static struct kvm_shared_msrs_global __read_mostly shared_msrs_global;
static struct kvm_shared_msrs __percpu *shared_msrs;

+static u64 __read_mostly host_xss;
+
struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "pf_fixed", VCPU_STAT(pf_fixed) },
{ "pf_guest", VCPU_STAT(pf_guest) },
@@ -812,27 +814,39 @@ void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
}
EXPORT_SYMBOL_GPL(kvm_lmsw);

-void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu)
+void kvm_load_guest_xsave_controls(struct kvm_vcpu *vcpu)
{
if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&
!vcpu->guest_xcr0_loaded) {
/* kvm_set_xcr() also depends on this */
if (vcpu->arch.xcr0 != host_xcr0)
xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
+
+ if (kvm_x86_ops->xsaves_supported() &&
+ guest_cpuid_has(vcpu, X86_FEATURE_XSAVES) &&
+ vcpu->arch.ia32_xss != host_xss)
+ wrmsrl(MSR_IA32_XSS, vcpu->arch.ia32_xss);
+
vcpu->guest_xcr0_loaded = 1;
}
}
-EXPORT_SYMBOL_GPL(kvm_load_guest_xcr0);
+EXPORT_SYMBOL_GPL(kvm_load_guest_xsave_controls);

-void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu)
+void kvm_load_host_xsave_controls(struct kvm_vcpu *vcpu)
{
if (vcpu->guest_xcr0_loaded) {
if (vcpu->arch.xcr0 != host_xcr0)
xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0);
+
+ if (kvm_x86_ops->xsaves_supported() &&
+ guest_cpuid_has(vcpu, X86_FEATURE_XSAVES) &&
+ vcpu->arch.ia32_xss != host_xss)
+ wrmsrl(MSR_IA32_XSS, host_xss);
+
vcpu->guest_xcr0_loaded = 0;
}
}
-EXPORT_SYMBOL_GPL(kvm_put_guest_xcr0);
+EXPORT_SYMBOL_GPL(kvm_load_host_xsave_controls);

static int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
{
@@ -9293,6 +9307,9 @@ int kvm_arch_hardware_setup(void)
kvm_default_tsc_scaling_ratio = 1ULL << kvm_tsc_scaling_ratio_frac_bits;
}

+ if (boot_cpu_has(X86_FEATURE_XSAVES))
+ rdmsrl(MSR_IA32_XSS, host_xss);
+
kvm_init_msr_list();
return 0;
}
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index dbf7442a822b..0d04e865665b 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -366,7 +366,7 @@ static inline bool kvm_pat_valid(u64 data)
return (data | ((data & 0x0202020202020202ull) << 1)) == data;
}

-void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu);
-void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu);
+void kvm_load_guest_xsave_controls(struct kvm_vcpu *vcpu);
+void kvm_load_host_xsave_controls(struct kvm_vcpu *vcpu);

#endif
--
2.23.0.581.g78d2f28ef7-goog