x86/bugs, KVM: Support the combination of guest and host IBRS

[mirror_ubuntu-artful-kernel.git] / arch / x86 / kvm / svm.c

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index af256b786a70cccd14906fe926e2b790156967a4..f9e7ddd56ea6e480fe41bd290884fd401c6bd93b 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -45,6 +45,7 @@
 #include <asm/debugreg.h>
 #include <asm/kvm_para.h>
 #include <asm/irq_remapping.h>
+#include <asm/nospec-branch.h>
 
 #include <asm/virtext.h>
 #include "trace.h"
@@ -175,6 +176,8 @@ struct vcpu_svm {
 
        u64 next_rip;
 
+       u64 spec_ctrl;
+
        u64 host_user_msrs[NR_HOST_SAVE_USER_MSRS];
        struct {
                u16 fs;
@@ -248,6 +251,8 @@ static const struct svm_direct_access_msrs {
        { .index = MSR_CSTAR,                           .always = true  },
        { .index = MSR_SYSCALL_MASK,                    .always = true  },
 #endif
+       { .index = MSR_IA32_SPEC_CTRL,                  .always = true },
+       { .index = MSR_IA32_PRED_CMD,                   .always = true },
        { .index = MSR_IA32_LASTBRANCHFROMIP,           .always = false },
        { .index = MSR_IA32_LASTBRANCHTOIP,             .always = false },
        { .index = MSR_IA32_LASTINTFROMIP,              .always = false },
@@ -514,6 +519,8 @@ struct svm_cpu_data {
        struct kvm_ldttss_desc *tss_desc;
 
        struct page *save_area;
+
+       struct vmcb *current_vmcb;
 };
 
 static DEFINE_PER_CPU(struct svm_cpu_data *, svm_data);
@@ -1681,11 +1688,19 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
        __free_pages(virt_to_page(svm->nested.msrpm), MSRPM_ALLOC_ORDER);
        kvm_vcpu_uninit(vcpu);
        kmem_cache_free(kvm_vcpu_cache, svm);
+
+       /*
+        * The VMCB could be recycled, causing a false negative in svm_vcpu_load;
+        * block speculative execution.
+        */
+       if (ibpb_inuse)
+               wrmsrl(MSR_IA32_PRED_CMD, FEATURE_SET_IBPB);
 }
 
 static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
+       struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
        int i;
 
        if (unlikely(cpu != vcpu->cpu)) {
@@ -1714,6 +1729,12 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
        if (static_cpu_has(X86_FEATURE_RDTSCP))
                wrmsrl(MSR_TSC_AUX, svm->tsc_aux);
 
+       if (sd->current_vmcb != svm->vmcb) {
+               sd->current_vmcb = svm->vmcb;
+               if (ibpb_inuse)
+                       wrmsrl(MSR_IA32_PRED_CMD, FEATURE_SET_IBPB);
+       }
+
        avic_vcpu_load(vcpu, cpu);
 }
 
@@ -3545,6 +3566,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
        case MSR_VM_CR:
                msr_info->data = svm->nested.vm_cr_msr;
                break;
+       case MSR_IA32_SPEC_CTRL:
+               msr_info->data = svm->spec_ctrl;
+               break;
        case MSR_IA32_UCODE_REV:
                msr_info->data = 0x01000065;
                break;
@@ -3693,6 +3717,9 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
        case MSR_VM_IGNNE:
                vcpu_unimpl(vcpu, "unimplemented wrmsr: 0x%x data 0x%llx\n", ecx, data);
                break;
+       case MSR_IA32_SPEC_CTRL:
+               svm->spec_ctrl = data;
+               break;
        case MSR_IA32_APICBASE:
                if (kvm_vcpu_apicv_active(vcpu))
                        avic_update_vapic_bar(to_svm(vcpu), data);
@@ -4874,6 +4901,9 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
 
        local_irq_enable();
 
+       /* SMB: Don't care about ibrs_inuse but rely on guest value */
+       x86_spec_ctrl_set_guest(svm->spec_ctrl);
+
        asm volatile (
                "push %%" _ASM_BP "; \n\t"
                "mov %c[rbx](%[svm]), %%" _ASM_BX " \n\t"
@@ -4917,6 +4947,25 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
                "mov %%r13, %c[r13](%[svm]) \n\t"
                "mov %%r14, %c[r14](%[svm]) \n\t"
                "mov %%r15, %c[r15](%[svm]) \n\t"
+#endif
+               /*
+               * Clear host registers marked as clobbered to prevent
+               * speculative use.
+               */
+               "xor %%" _ASM_BX ", %%" _ASM_BX " \n\t"
+               "xor %%" _ASM_CX ", %%" _ASM_CX " \n\t"
+               "xor %%" _ASM_DX ", %%" _ASM_DX " \n\t"
+               "xor %%" _ASM_SI ", %%" _ASM_SI " \n\t"
+               "xor %%" _ASM_DI ", %%" _ASM_DI " \n\t"
+#ifdef CONFIG_X86_64
+               "xor %%r8, %%r8 \n\t"
+               "xor %%r9, %%r9 \n\t"
+               "xor %%r10, %%r10 \n\t"
+               "xor %%r11, %%r11 \n\t"
+               "xor %%r12, %%r12 \n\t"
+               "xor %%r13, %%r13 \n\t"
+               "xor %%r14, %%r14 \n\t"
+               "xor %%r15, %%r15 \n\t"
 #endif
                "pop %%" _ASM_BP
                :
@@ -4947,6 +4996,11 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
 #endif
                );
 
+       /* Eliminate branch target predictions from guest mode */
+       vmexit_fill_RSB();
+
+       x86_spec_ctrl_restore_host(svm->spec_ctrl);
+
 #ifdef CONFIG_X86_64
        wrmsrl(MSR_GS_BASE, svm->host.gs_base);
 #else