[PATCH v7 1/7] KVM: CPUID: Fix IA32_XSS support in CPUID(0xd,i) enumeration

Yang Weijiang
2019-09-27T02:17:46Z

The control bits in IA32_XSS MSR are being used for new features,
but current CPUID(0xd,i) enumeration code doesn't support them, so
fix existing code first.

The supervisor states in IA32_XSS haven't been used in public
KVM code, so set KVM_SUPPORTED_XSS to 0 now, anyone who's developing
IA32_XSS related feature may expand the macro to add the CPUID support,
otherwise, CPUID(0xd,i>1) always reports 0 of the subleaf to guest.

Extracted old code into a new filter and keep it same flavor as others.

This patch passed selftest on a few Intel platforms.

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/cpuid.c | 94 +++++++++++++++++++++------------
arch/x86/kvm/svm.c | 7 +++
arch/x86/kvm/vmx/vmx.c | 6 +++
arch/x86/kvm/x86.h | 7 +++
5 files changed, 82 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 74e88e5edd9c..d018df8c5f32 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1209,6 +1209,7 @@ struct kvm_x86_ops {
uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);

bool (*need_emulation_on_page_fault)(struct kvm_vcpu *vcpu);
+ u64 (*supported_xss)(void);
};

struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 22c2720cd948..9d282fec0a62 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -62,6 +62,11 @@ u64 kvm_supported_xcr0(void)
return xcr0;
}

+u64 kvm_supported_xss(void)
+{
+ return KVM_SUPPORTED_XSS & kvm_x86_ops->supported_xss();
+}
+
#define F(x) bit(X86_FEATURE_##x)

int kvm_update_cpuid(struct kvm_vcpu *vcpu)
@@ -414,6 +419,50 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
}
}

+static inline void do_cpuid_0xd_mask(struct kvm_cpuid_entry2 *entry, int index)
+{
+ unsigned int f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;
+ /* cpuid 0xD.1.eax */
+ const u32 kvm_cpuid_D_1_eax_x86_features =
+ F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | f_xsaves;
+ u64 u_supported = kvm_supported_xcr0();
+ u64 s_supported = kvm_supported_xss();
+ u64 supported;
+
+ switch (index) {
+ case 0:
+ entry->eax &= u_supported;
+ entry->ebx = xstate_required_size(u_supported, false);
+ entry->ecx = entry->ebx;
+ entry->edx = 0;
+ break;
+ case 1:
+ supported = u_supported | s_supported;
+ entry->eax &= kvm_cpuid_D_1_eax_x86_features;
+ cpuid_mask(&entry->eax, CPUID_D_1_EAX);
+ entry->ebx = 0;
+ entry->edx = 0;
+ entry->ecx &= s_supported;
+ if (entry->eax & (F(XSAVES) | F(XSAVEC)))
+ entry->ebx = xstate_required_size(supported, true);
+
+ break;
+ default:
+ supported = (entry->ecx & 1) ? s_supported : u_supported;
+ if (!(supported & ((u64)1 << index))) {
+ entry->eax = 0;
+ entry->ebx = 0;
+ entry->ecx = 0;
+ entry->edx = 0;
+ return;
+ }
+ if (entry->ecx)
+ entry->ebx = 0;
+ entry->edx = 0;
+ break;
+ }
+}
+
static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
int *nent, int maxnent)
{
@@ -428,7 +477,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
unsigned f_lm = 0;
#endif
unsigned f_rdtscp = kvm_x86_ops->rdtscp_supported() ? F(RDTSCP) : 0;
- unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;
unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? F(INTEL_PT) : 0;

/* cpuid 1.edx */
@@ -482,10 +530,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
F(ACE2) | F(ACE2_EN) | F(PHE) | F(PHE_EN) |
F(PMM) | F(PMM_EN);

- /* cpuid 0xD.1.eax */
- const u32 kvm_cpuid_D_1_eax_x86_features =
- F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | f_xsaves;
-
/* all calls to cpuid_count() should be made on the same cpu */
get_cpu();

@@ -622,38 +666,22 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
break;
}
case 0xd: {
- int idx, i;
- u64 supported = kvm_supported_xcr0();
-
- entry->eax &= supported;
- entry->ebx = xstate_required_size(supported, false);
- entry->ecx = entry->ebx;
- entry->edx &= supported >> 32;
- if (!supported)
- break;
+ int i, idx;

- for (idx = 1, i = 1; idx < 64; ++idx) {
- u64 mask = ((u64)1 << idx);
+ do_cpuid_0xd_mask(&entry[0], 0);
+ for (i = 1, idx = 1; idx < 64; ++idx) {
if (*nent >= maxnent)
goto out;
-
do_host_cpuid(&entry[i], function, idx);
- if (idx == 1) {
- entry[i].eax &= kvm_cpuid_D_1_eax_x86_features;
- cpuid_mask(&entry[i].eax, CPUID_D_1_EAX);
- entry[i].ebx = 0;
- if (entry[i].eax & (F(XSAVES)|F(XSAVEC)))
- entry[i].ebx =
- xstate_required_size(supported,
- true);
- } else {
- if (entry[i].eax == 0 || !(supported & mask))
- continue;
- if (WARN_ON_ONCE(entry[i].ecx & 1))
- continue;
- }
- entry[i].ecx = 0;
- entry[i].edx = 0;
+ if (entry[i].eax == 0 && entry[i].ebx == 0 &&
+ entry[i].ecx == 0 && entry[i].edx == 0)
+ continue;
+
+ do_cpuid_0xd_mask(&entry[i], idx);
+ if (entry[i].eax == 0 && entry[i].ebx == 0 &&
+ entry[i].ecx == 0 && entry[i].edx == 0)
+ continue;
+
++*nent;
++i;
}
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index e0368076a1ef..be967bf9a81d 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7193,6 +7193,11 @@ static bool svm_need_emulation_on_page_fault(struct kvm_vcpu *vcpu)
return false;
}

+static u64 svm_supported_xss(void)
+{
+ return 0;
+}
+
static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
.cpu_has_kvm_support = has_svm,
.disabled_by_bios = is_disabled,
@@ -7329,6 +7334,8 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
.nested_get_evmcs_version = NULL,

.need_emulation_on_page_fault = svm_need_emulation_on_page_fault,
+
+ .supported_xss = svm_supported_xss,
};

static int __init svm_init(void)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c6f6b05004d9..a84198cff397 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1651,6 +1651,11 @@ static inline bool vmx_feature_control_msr_valid(struct kvm_vcpu *vcpu,
return !(val & ~valid_bits);
}

+static inline u64 vmx_supported_xss(void)
+{
+ return host_xss;
+}
+
static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
{
switch (msr->index) {
@@ -7799,6 +7804,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
.nested_enable_evmcs = NULL,
.nested_get_evmcs_version = NULL,
.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
+ .supported_xss = vmx_supported_xss,
};

static void vmx_cleanup_l1d_flush(void)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 6594020c0691..fbffabad0370 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -293,6 +293,13 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
| XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
| XFEATURE_MASK_PKRU)
+
+/*
+ * Right now, no XSS states are used on x86 platform,
+ * expand the macro for new features.
+ */
+#define KVM_SUPPORTED_XSS (0)
+
extern u64 host_xcr0;

extern u64 kvm_supported_xcr0(void);
--
2.17.2