KVM: CPUID: add support for supervisor states

Current CPUID 0xd enumeration code does not support supervisor
states, because KVM only supports setting IA32_XSS to zero.
Change it instead to use a new variable supported_xss, to be
set from the hardware_setup callback which is in charge of CPU
capabilities.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index cc8b24b..78d461b 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -642,15 +642,22 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 
                cpuid_entry_override(entry, CPUID_D_1_EAX);
                if (entry->eax & (F(XSAVES)|F(XSAVEC)))
-                       entry->ebx = xstate_required_size(supported_xcr0, true);
-               else
+                       entry->ebx = xstate_required_size(supported_xcr0 | supported_xss,
+                                                         true);
+               else {
+                       WARN_ON_ONCE(supported_xss != 0);
                        entry->ebx = 0;
-               /* Saving XSS controlled state via XSAVES isn't supported. */
-               entry->ecx = 0;
-               entry->edx = 0;
+               }
+               entry->ecx &= supported_xss;
+               entry->edx &= supported_xss >> 32;
 
                for (i = 2; i < 64; ++i) {
-                       if (!(supported_xcr0 & BIT_ULL(i)))
+                       bool s_state;
+                       if (supported_xcr0 & BIT_ULL(i))
+                               s_state = false;
+                       else if (supported_xss & BIT_ULL(i))
+                               s_state = true;
+                       else
                                continue;
 
                        entry = do_host_cpuid(array, function, i);
@@ -659,17 +666,16 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 
                        /*
                         * The supported check above should have filtered out
-                        * invalid sub-leafs as well as sub-leafs managed by
-                        * IA32_XSS MSR.  Only XCR0-managed sub-leafs should
+                        * invalid sub-leafs.  Only valid sub-leafs should
                         * reach this point, and they should have a non-zero
-                        * save state size.
+                        * save state size.  Furthermore, check whether the
+                        * processor agrees with supported_xcr0/supported_xss
+                        * on whether this is an XCR0- or IA32_XSS-managed area.
                         */
-                       if (WARN_ON_ONCE(!entry->eax || (entry->ecx & 1))) {
+                       if (WARN_ON_ONCE(!entry->eax || (entry->ecx & 0x1) != s_state)) {
                                --array->nent;
                                continue;
                        }
-
-                       entry->ecx = 0;
                        entry->edx = 0;
                }
                break;

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index c6e9910..4dca357 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1371,6 +1371,8 @@ static __init void svm_set_cpu_caps(void)
 {
        kvm_set_cpu_caps();
 
+       supported_xss = 0;
+
        /* CPUID 0x80000001 and 0x8000000A (SVM features) */
        if (nested) {
                kvm_cpu_cap_set(X86_FEATURE_SVM);

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e91a84b..8001070 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7126,6 +7126,7 @@ static __init void vmx_set_cpu_caps(void)
                kvm_cpu_cap_set(X86_FEATURE_UMIP);
 
        /* CPUID 0xD.1 */
+       supported_xss = 0;
        if (!vmx_xsaves_supported())
                kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
 

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d2f1b47..96e897d 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -190,6 +190,8 @@ u64 __read_mostly host_efer;
 EXPORT_SYMBOL_GPL(host_efer);
 
 static u64 __read_mostly host_xss;
+u64 __read_mostly supported_xss;
+EXPORT_SYMBOL_GPL(supported_xss);
 
 struct kvm_stats_debugfs_item debugfs_entries[] = {
        { "pf_fixed", VCPU_STAT(pf_fixed) },
@@ -2827,7 +2829,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                 * IA32_XSS[bit 8]. Guests have to use RDMSR/WRMSR rather than
                 * XSAVES/XRSTORS to save/restore PT MSRs.
                 */
-               if (data != 0)
+               if (data & ~supported_xss)
                        return 1;
                vcpu->arch.ia32_xss = data;
                break;
@@ -9617,10 +9619,16 @@ int kvm_arch_hardware_setup(void)
 
        rdmsrl_safe(MSR_EFER, &host_efer);
 
+       if (boot_cpu_has(X86_FEATURE_XSAVES))
+               rdmsrl(MSR_IA32_XSS, host_xss);
+
        r = kvm_x86_ops->hardware_setup();
        if (r != 0)
                return r;
 
+       if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
+               supported_xss = 0;
+
        cr4_reserved_bits = kvm_host_cr4_reserved_bits(&boot_cpu_data);
 
        if (kvm_has_tsc_control) {
@@ -9637,9 +9645,6 @@ 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 4d890bf..c1954e2 100644 (file)
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -272,6 +272,7 @@ enum exit_fastpath_completion handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vc
 
 extern u64 host_xcr0;
 extern u64 supported_xcr0;
+extern u64 supported_xss;
 
 static inline bool kvm_mpx_supported(void)
 {