Commit 2a9758c5 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

target/i386: add support for MSR_IA32_TSX_CTRL 



The MSR_IA32_TSX_CTRL MSR can be used to hide TSX (also known as the
Trusty Side-channel Extension).  By virtualizing the MSR, KVM guests
can disable TSX and avoid paying the price of mitigating TSX-based
attacks on microarchitectural side channels.

Reviewed-by: default avatarEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 0723cc8a

target/i386/cpu.c

+1 −1
Original line number Diff line number Diff line
@@ -1204,7 +1204,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = { 
        .type = MSR_FEATURE_WORD,

        .feat_names = {

            "rdctl-no", "ibrs-all", "rsba", "skip-l1dfl-vmentry",

            "ssb-no", "mds-no", "pschange-mc-no", NULL,

            "ssb-no", "mds-no", "pschange-mc-no", "tsx-ctrl",

            "taa-no", NULL, NULL, NULL,

            NULL, NULL, NULL, NULL,

            NULL, NULL, NULL, NULL,

target/i386/cpu.h

+5 −0
Original line number Diff line number Diff line
@@ -349,7 +349,11 @@ typedef enum X86Seg { 
#define MSR_VIRT_SSBD                   0xc001011f

#define MSR_IA32_PRED_CMD               0x49

#define MSR_IA32_CORE_CAPABILITY        0xcf



#define MSR_IA32_ARCH_CAPABILITIES      0x10a

#define ARCH_CAP_TSX_CTRL_MSR		(1<<7)



#define MSR_IA32_TSX_CTRL		0x122

#define MSR_IA32_TSCDEADLINE            0x6e0



#define FEATURE_CONTROL_LOCKED                    (1<<0)
@@ -1449,6 +1453,7 @@ typedef struct CPUX86State { 
    uint64_t msr_smi_count;



    uint32_t pkru;

    uint32_t tsx_ctrl;



    uint64_t spec_ctrl;

    uint64_t virt_ssbd;

target/i386/kvm.c

+13 −0
Original line number Diff line number Diff line
@@ -97,6 +97,7 @@ static bool has_msr_hv_reenlightenment; 
static bool has_msr_xss;

static bool has_msr_umwait;

static bool has_msr_spec_ctrl;

static bool has_msr_tsx_ctrl;

static bool has_msr_virt_ssbd;

static bool has_msr_smi_count;

static bool has_msr_arch_capabs;
@@ -2036,6 +2037,9 @@ static int kvm_get_supported_msrs(KVMState *s) 
            case MSR_IA32_SPEC_CTRL:

                has_msr_spec_ctrl = true;

                break;

            case MSR_IA32_TSX_CTRL:

                has_msr_tsx_ctrl = true;

                break;

            case MSR_VIRT_SSBD:

                has_msr_virt_ssbd = true;

                break;
@@ -2694,6 +2698,9 @@ static int kvm_put_msrs(X86CPU *cpu, int level) 
    if (has_msr_spec_ctrl) {

        kvm_msr_entry_add(cpu, MSR_IA32_SPEC_CTRL, env->spec_ctrl);

    }

    if (has_msr_tsx_ctrl) {

        kvm_msr_entry_add(cpu, MSR_IA32_TSX_CTRL, env->tsx_ctrl);

    }

    if (has_msr_virt_ssbd) {

        kvm_msr_entry_add(cpu, MSR_VIRT_SSBD, env->virt_ssbd);

    }
@@ -3110,6 +3117,9 @@ static int kvm_get_msrs(X86CPU *cpu) 
    if (has_msr_spec_ctrl) {

        kvm_msr_entry_add(cpu, MSR_IA32_SPEC_CTRL, 0);

    }

    if (has_msr_tsx_ctrl) {

        kvm_msr_entry_add(cpu, MSR_IA32_TSX_CTRL, 0);

    }

    if (has_msr_virt_ssbd) {

        kvm_msr_entry_add(cpu, MSR_VIRT_SSBD, 0);

    }
@@ -3502,6 +3512,9 @@ static int kvm_get_msrs(X86CPU *cpu) 
        case MSR_IA32_SPEC_CTRL:

            env->spec_ctrl = msrs[i].data;

            break;

        case MSR_IA32_TSX_CTRL:

            env->tsx_ctrl = msrs[i].data;

            break;

        case MSR_VIRT_SSBD:

            env->virt_ssbd = msrs[i].data;

            break;

target/i386/machine.c

+20 −0
Original line number Diff line number Diff line
@@ -1293,6 +1293,25 @@ static const VMStateDescription vmstate_efer32 = { 
};

#endif



static bool msr_tsx_ctrl_needed(void *opaque)

{

    X86CPU *cpu = opaque;

    CPUX86State *env = &cpu->env;



    return env->features[FEAT_ARCH_CAPABILITIES] & ARCH_CAP_TSX_CTRL_MSR;

}



static const VMStateDescription vmstate_msr_tsx_ctrl = {

    .name = "cpu/msr_tsx_ctrl",

    .version_id = 1,

    .minimum_version_id = 1,

    .needed = msr_tsx_ctrl_needed,

    .fields = (VMStateField[]) {

        VMSTATE_UINT32(env.tsx_ctrl, X86CPU),

        VMSTATE_END_OF_LIST()

    }

};



VMStateDescription vmstate_x86_cpu = {

    .name = "cpu",

    .version_id = 12,
@@ -1427,6 +1446,7 @@ VMStateDescription vmstate_x86_cpu = { 
#ifdef CONFIG_KVM

        &vmstate_nested_state,

#endif

        &vmstate_msr_tsx_ctrl,

        NULL

    }

};