KVM: VMX: Enable XSAVE/XRSTOR for guest

This patch enable guest to use XSAVE/XRSTOR instructions.

We assume that host_xcr0 would use all possible bits that OS supported.

And we loaded xcr0 in the same way we handled fpu - do it as late as we can.

Signed-off-by: Dexuan Cui <dexuan.cui@intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

6 files changed, 146 insertions, 8 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0cd0f2923af5..91631b8b2090 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -302,6 +302,7 @@ struct kvm_vcpu_arch {
         } update_pte;
 
         struct fpu guest_fpu;
+        u64 xcr0;
 
         gva_t mmio_fault_cr2;
         struct kvm_pio_request pio;
@@ -605,6 +606,7 @@ int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val);
 unsigned long kvm_get_cr8(struct kvm_vcpu *vcpu);
 void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw);
 void kvm_get_cs_db_l_bits(struct kvm_vcpu *vcpu, int *db, int *l);
+int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr);
 
 int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
 int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data);
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 96a5886d384e..9f0cbd987d50 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -267,6 +267,7 @@ enum vmcs_field {
 #define EXIT_REASON_EPT_VIOLATION       48
 #define EXIT_REASON_EPT_MISCONFIG       49
 #define EXIT_REASON_WBINVD              54
+#define EXIT_REASON_XSETBV              55
 
 /*
  * Interruption-information format
diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h
index d2a98f8f9af5..6491ac8e755b 100644
--- a/arch/x86/kvm/kvm_cache_regs.h
+++ b/arch/x86/kvm/kvm_cache_regs.h
@@ -71,4 +71,10 @@ static inline ulong kvm_read_cr4(struct kvm_vcpu *vcpu)
         return kvm_read_cr4_bits(vcpu, ~0UL);
 }
 
+static inline u64 kvm_read_edx_eax(struct kvm_vcpu *vcpu)
+{
+        return (kvm_register_read(vcpu, VCPU_REGS_RAX) & -1u)
+                | ((u64)(kvm_register_read(vcpu, VCPU_REGS_RDX) & -1u) << 32);
+}
+
 #endif
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 26ba61d6af8c..864a1b6d155a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -37,6 +37,8 @@
 #include <asm/vmx.h>
 #include <asm/virtext.h>
 #include <asm/mce.h>
+#include <asm/i387.h>
+#include <asm/xcr.h>
 
 #include "trace.h"
 
@@ -3390,6 +3392,16 @@ static int handle_wbinvd(struct kvm_vcpu *vcpu)
         return 1;
 }
 
+static int handle_xsetbv(struct kvm_vcpu *vcpu)
+{
+        u64 new_bv = kvm_read_edx_eax(vcpu);
+        u32 index = kvm_register_read(vcpu, VCPU_REGS_RCX);
+
+        if (kvm_set_xcr(vcpu, index, new_bv) == 0)
+                skip_emulated_instruction(vcpu);
+        return 1;
+}
+
 static int handle_apic_access(struct kvm_vcpu *vcpu)
 {
         return emulate_instruction(vcpu, 0, 0, 0) == EMULATE_DONE;
@@ -3668,6 +3680,7 @@ static int (*kvm_vmx_exit_handlers[])(struct kvm_vcpu *vcpu) = {
         [EXIT_REASON_TPR_BELOW_THRESHOLD]     = handle_tpr_below_threshold,
         [EXIT_REASON_APIC_ACCESS]             = handle_apic_access,
         [EXIT_REASON_WBINVD]                  = handle_wbinvd,
+        [EXIT_REASON_XSETBV]                  = handle_xsetbv,
         [EXIT_REASON_TASK_SWITCH]             = handle_task_switch,
         [EXIT_REASON_MCE_DURING_VMENTRY]      = handle_machine_check,
         [EXIT_REASON_EPT_VIOLATION]           = handle_ept_violation,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b08c0052e332..b5e644701cc1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -65,6 +65,7 @@
         (~(unsigned long)(X86_CR4_VME | X86_CR4_PVI | X86_CR4_TSD | X86_CR4_DE\
                           | X86_CR4_PSE | X86_CR4_PAE | X86_CR4_MCE     \
                           | X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR  \
+                          | X86_CR4_OSXSAVE \
                           | X86_CR4_OSXMMEXCPT | X86_CR4_VMXE))
 
 #define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
@@ -150,6 +151,13 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { NULL }
 };
 
+u64 __read_mostly host_xcr0;
+
+static inline u32 bit(int bitno)
+{
+        return 1 << (bitno & 31);
+}
+
 static void kvm_on_user_return(struct user_return_notifier *urn)
 {
         unsigned slot;
@@ -474,6 +482,61 @@ void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
 }
 EXPORT_SYMBOL_GPL(kvm_lmsw);
 
+int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
+{
+        u64 xcr0;
+
+        /* Only support XCR_XFEATURE_ENABLED_MASK(xcr0) now  */
+        if (index != XCR_XFEATURE_ENABLED_MASK)
+                return 1;
+        xcr0 = xcr;
+        if (kvm_x86_ops->get_cpl(vcpu) != 0)
+                return 1;
+        if (!(xcr0 & XSTATE_FP))
+                return 1;
+        if ((xcr0 & XSTATE_YMM) && !(xcr0 & XSTATE_SSE))
+                return 1;
+        if (xcr0 & ~host_xcr0)
+                return 1;
+        vcpu->arch.xcr0 = xcr0;
+        vcpu->guest_xcr0_loaded = 0;
+        return 0;
+}
+
+int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
+{
+        if (__kvm_set_xcr(vcpu, index, xcr)) {
+                kvm_inject_gp(vcpu, 0);
+                return 1;
+        }
+        return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_set_xcr);
+
+static bool guest_cpuid_has_xsave(struct kvm_vcpu *vcpu)
+{
+        struct kvm_cpuid_entry2 *best;
+
+        best = kvm_find_cpuid_entry(vcpu, 1, 0);
+        return best && (best->ecx & bit(X86_FEATURE_XSAVE));
+}
+
+static void update_cpuid(struct kvm_vcpu *vcpu)
+{
+        struct kvm_cpuid_entry2 *best;
+
+        best = kvm_find_cpuid_entry(vcpu, 1, 0);
+        if (!best)
+                return;
+
+        /* Update OSXSAVE bit */
+        if (cpu_has_xsave && best->function == 0x1) {
+                best->ecx &= ~(bit(X86_FEATURE_OSXSAVE));
+                if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE))
+                        best->ecx |= bit(X86_FEATURE_OSXSAVE);
+        }
+}
+
 int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 {
         unsigned long old_cr4 = kvm_read_cr4(vcpu);
@@ -482,6 +545,9 @@ int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
         if (cr4 & CR4_RESERVED_BITS)
                 return 1;
 
+        if (!guest_cpuid_has_xsave(vcpu) && (cr4 & X86_CR4_OSXSAVE))
+                return 1;
+
         if (is_long_mode(vcpu)) {
                 if (!(cr4 & X86_CR4_PAE))
                         return 1;
@@ -498,6 +564,9 @@ int __kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
         if ((cr4 ^ old_cr4) & pdptr_bits)
                 kvm_mmu_reset_context(vcpu);
 
+        if ((cr4 ^ old_cr4) & X86_CR4_OSXSAVE)
+                update_cpuid(vcpu);
+
         return 0;
 }
 
@@ -666,11 +735,6 @@ int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
 }
 EXPORT_SYMBOL_GPL(kvm_get_dr);
 
-static inline u32 bit(int bitno)
-{
-        return 1 << (bitno & 31);
-}
-
 /*
  * List of msr numbers which we expose to userspace through KVM_GET_MSRS
  * and KVM_SET_MSRS, and KVM_GET_MSR_INDEX_LIST.
@@ -1814,6 +1878,7 @@ static int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
         r = 0;
         kvm_apic_set_version(vcpu);
         kvm_x86_ops->cpuid_update(vcpu);
+        update_cpuid(vcpu);
 
 out_free:
         vfree(cpuid_entries);
@@ -1837,6 +1902,7 @@ static int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
         vcpu->arch.cpuid_nent = cpuid->nent;
         kvm_apic_set_version(vcpu);
         kvm_x86_ops->cpuid_update(vcpu);
+        update_cpuid(vcpu);
         return 0;
 
 out:
@@ -1917,7 +1983,7 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
                 0 /* Reserved */ | F(CX16) | 0 /* xTPR Update, PDCM */ |
                 0 /* Reserved, DCA */ | F(XMM4_1) |
                 F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) |
-                0 /* Reserved, XSAVE, OSXSAVE */;
+                0 /* Reserved, AES */ | F(XSAVE) | 0 /* OSXSAVE */;
         /* cpuid 0x80000001.ecx */
         const u32 kvm_supported_word6_x86_features =
                 F(LAHF_LM) | F(CMP_LEGACY) | F(SVM) | 0 /* ExtApicSpace */ |
@@ -1932,7 +1998,7 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 
         switch (function) {
         case 0:
-                entry->eax = min(entry->eax, (u32)0xb);
+                entry->eax = min(entry->eax, (u32)0xd);
                 break;
         case 1:
                 entry->edx &= kvm_supported_word0_x86_features;
@@ -1990,6 +2056,20 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
                 }
                 break;
         }
+        case 0xd: {
+                int i;
+
+                entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+                for (i = 1; *nent < maxnent; ++i) {
+                        if (entry[i - 1].eax == 0 && i != 2)
+                                break;
+                        do_cpuid_1_ent(&entry[i], function, i);
+                        entry[i].flags |=
+                               KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
+                        ++*nent;
+                }
+                break;
+        }
         case KVM_CPUID_SIGNATURE: {
                 char signature[12] = "KVMKVMKVM\0\0";
                 u32 *sigptr = (u32 *)signature;
@@ -4125,6 +4205,9 @@ int kvm_arch_init(void *opaque)
 
         perf_register_guest_info_callbacks(&kvm_guest_cbs);
 
+        if (cpu_has_xsave)
+                host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
+
         return 0;
 
 out:
@@ -4523,6 +4606,25 @@ static void inject_pending_event(struct kvm_vcpu *vcpu)
         }
 }
 
+static void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu)
+{
+        if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&
+                        !vcpu->guest_xcr0_loaded) {
+                /* kvm_set_xcr() also depends on this */
+                xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
+                vcpu->guest_xcr0_loaded = 1;
+        }
+}
+
+static void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu)
+{
+        if (vcpu->guest_xcr0_loaded) {
+                if (vcpu->arch.xcr0 != host_xcr0)
+                        xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0);
+                vcpu->guest_xcr0_loaded = 0;
+        }
+}
+
 static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 {
         int r;
@@ -4568,6 +4670,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
         kvm_x86_ops->prepare_guest_switch(vcpu);
         if (vcpu->fpu_active)
                 kvm_load_guest_fpu(vcpu);
+        kvm_load_guest_xcr0(vcpu);
 
         atomic_set(&vcpu->guest_mode, 1);
         smp_wmb();
@@ -5124,6 +5227,11 @@ int fx_init(struct kvm_vcpu *vcpu)
 
         fpu_finit(&vcpu->arch.guest_fpu);
 
+        /*
+         * Ensure guest xcr0 is valid for loading
+         */
+        vcpu->arch.xcr0 = XSTATE_FP;
+
         vcpu->arch.cr0 |= X86_CR0_ET;
 
         return 0;
@@ -5140,6 +5248,12 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
         if (vcpu->guest_fpu_loaded)
                 return;
 
+        /*
+         * Restore all possible states in the guest,
+         * and assume host would use all available bits.
+         * Guest xcr0 would be loaded later.
+         */
+        kvm_put_guest_xcr0(vcpu);
         vcpu->guest_fpu_loaded = 1;
         unlazy_fpu(current);
         fpu_restore_checking(&vcpu->arch.guest_fpu);
@@ -5148,6 +5262,8 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 
 void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
 {
+        kvm_put_guest_xcr0(vcpu);
+
         if (!vcpu->guest_fpu_loaded)
                 return;
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2c62319727ef..2d96555cd4ed 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -88,7 +88,7 @@ struct kvm_vcpu {
         int srcu_idx;
 
         int fpu_active;
-        int guest_fpu_loaded;
+        int guest_fpu_loaded, guest_xcr0_loaded;
         wait_queue_head_t wq;
         int sigset_active;
         sigset_t sigset;