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KVM: SVM: Add initial support for a VMGEXIT VMEXIT
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SEV-ES adds a new VMEXIT reason code, VMGEXIT. Initial support for a
VMGEXIT includes mapping the GHCB based on the guest GPA, which is
obtained from a new VMCB field, and then validating the required inputs
for the VMGEXIT exit reason.

Since many of the VMGEXIT exit reasons correspond to existing VMEXIT
reasons, the information from the GHCB is copied into the VMCB control
exit code areas and KVM register areas. The standard exit handlers are
invoked, similar to standard VMEXIT processing. Before restarting the
vCPU, the GHCB is updated with any registers that have been updated by
the hypervisor.

Signed-off-by: Tom Lendacky <[email protected]>
Message-Id: <c6a4ed4294a369bd75c44d03bd7ce0f0c3840e50.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <[email protected]>
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@tlendacky @bonzini
tlendacky authored and bonzini committed Dec 15, 2020
1 parent e9093fd commit 291bd20
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Showing 5 changed files with 292 additions and 3 deletions.
2 changes: 1 addition & 1 deletion arch/x86/include/asm/svm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -130,7 +130,7 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
u32 exit_int_info_err;
u64 nested_ctl;
u64 avic_vapic_bar;
u8 reserved_4[8];
u64 ghcb_gpa;
u32 event_inj;
u32 event_inj_err;
u64 nested_cr3;
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7 changes: 7 additions & 0 deletions arch/x86/include/uapi/asm/svm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,7 @@
#define SVM_EXIT_NPF 0x400
#define SVM_EXIT_AVIC_INCOMPLETE_IPI 0x401
#define SVM_EXIT_AVIC_UNACCELERATED_ACCESS 0x402
#define SVM_EXIT_VMGEXIT 0x403

/* SEV-ES software-defined VMGEXIT events */
#define SVM_VMGEXIT_MMIO_READ 0x80000001
Expand Down Expand Up @@ -187,6 +188,12 @@
{ SVM_EXIT_NPF, "npf" }, \
{ SVM_EXIT_AVIC_INCOMPLETE_IPI, "avic_incomplete_ipi" }, \
{ SVM_EXIT_AVIC_UNACCELERATED_ACCESS, "avic_unaccelerated_access" }, \
{ SVM_EXIT_VMGEXIT, "vmgexit" }, \
{ SVM_VMGEXIT_MMIO_READ, "vmgexit_mmio_read" }, \
{ SVM_VMGEXIT_MMIO_WRITE, "vmgexit_mmio_write" }, \
{ SVM_VMGEXIT_NMI_COMPLETE, "vmgexit_nmi_complete" }, \
{ SVM_VMGEXIT_AP_HLT_LOOP, "vmgexit_ap_hlt_loop" }, \
{ SVM_VMGEXIT_AP_JUMP_TABLE, "vmgexit_ap_jump_table" }, \
{ SVM_EXIT_ERR, "invalid_guest_state" }


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272 changes: 272 additions & 0 deletions arch/x86/kvm/svm/sev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@

#include "x86.h"
#include "svm.h"
#include "cpuid.h"

static int sev_flush_asids(void);
static DECLARE_RWSEM(sev_deactivate_lock);
Expand Down Expand Up @@ -1257,11 +1258,226 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu)
__free_page(virt_to_page(svm->vmsa));
}

static void dump_ghcb(struct vcpu_svm *svm)
{
struct ghcb *ghcb = svm->ghcb;
unsigned int nbits;

/* Re-use the dump_invalid_vmcb module parameter */
if (!dump_invalid_vmcb) {
pr_warn_ratelimited("set kvm_amd.dump_invalid_vmcb=1 to dump internal KVM state.\n");
return;
}

nbits = sizeof(ghcb->save.valid_bitmap) * 8;

pr_err("GHCB (GPA=%016llx):\n", svm->vmcb->control.ghcb_gpa);
pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_code",
ghcb->save.sw_exit_code, ghcb_sw_exit_code_is_valid(ghcb));
pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_info_1",
ghcb->save.sw_exit_info_1, ghcb_sw_exit_info_1_is_valid(ghcb));
pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_info_2",
ghcb->save.sw_exit_info_2, ghcb_sw_exit_info_2_is_valid(ghcb));
pr_err("%-20s%016llx is_valid: %u\n", "sw_scratch",
ghcb->save.sw_scratch, ghcb_sw_scratch_is_valid(ghcb));
pr_err("%-20s%*pb\n", "valid_bitmap", nbits, ghcb->save.valid_bitmap);
}

static void sev_es_sync_to_ghcb(struct vcpu_svm *svm)
{
struct kvm_vcpu *vcpu = &svm->vcpu;
struct ghcb *ghcb = svm->ghcb;

/*
* The GHCB protocol so far allows for the following data
* to be returned:
* GPRs RAX, RBX, RCX, RDX
*
* Copy their values to the GHCB if they are dirty.
*/
if (kvm_register_is_dirty(vcpu, VCPU_REGS_RAX))
ghcb_set_rax(ghcb, vcpu->arch.regs[VCPU_REGS_RAX]);
if (kvm_register_is_dirty(vcpu, VCPU_REGS_RBX))
ghcb_set_rbx(ghcb, vcpu->arch.regs[VCPU_REGS_RBX]);
if (kvm_register_is_dirty(vcpu, VCPU_REGS_RCX))
ghcb_set_rcx(ghcb, vcpu->arch.regs[VCPU_REGS_RCX]);
if (kvm_register_is_dirty(vcpu, VCPU_REGS_RDX))
ghcb_set_rdx(ghcb, vcpu->arch.regs[VCPU_REGS_RDX]);
}

static void sev_es_sync_from_ghcb(struct vcpu_svm *svm)
{
struct vmcb_control_area *control = &svm->vmcb->control;
struct kvm_vcpu *vcpu = &svm->vcpu;
struct ghcb *ghcb = svm->ghcb;
u64 exit_code;

/*
* The GHCB protocol so far allows for the following data
* to be supplied:
* GPRs RAX, RBX, RCX, RDX
* XCR0
* CPL
*
* VMMCALL allows the guest to provide extra registers. KVM also
* expects RSI for hypercalls, so include that, too.
*
* Copy their values to the appropriate location if supplied.
*/
memset(vcpu->arch.regs, 0, sizeof(vcpu->arch.regs));

vcpu->arch.regs[VCPU_REGS_RAX] = ghcb_get_rax_if_valid(ghcb);
vcpu->arch.regs[VCPU_REGS_RBX] = ghcb_get_rbx_if_valid(ghcb);
vcpu->arch.regs[VCPU_REGS_RCX] = ghcb_get_rcx_if_valid(ghcb);
vcpu->arch.regs[VCPU_REGS_RDX] = ghcb_get_rdx_if_valid(ghcb);
vcpu->arch.regs[VCPU_REGS_RSI] = ghcb_get_rsi_if_valid(ghcb);

svm->vmcb->save.cpl = ghcb_get_cpl_if_valid(ghcb);

if (ghcb_xcr0_is_valid(ghcb)) {
vcpu->arch.xcr0 = ghcb_get_xcr0(ghcb);
kvm_update_cpuid_runtime(vcpu);
}

/* Copy the GHCB exit information into the VMCB fields */
exit_code = ghcb_get_sw_exit_code(ghcb);
control->exit_code = lower_32_bits(exit_code);
control->exit_code_hi = upper_32_bits(exit_code);
control->exit_info_1 = ghcb_get_sw_exit_info_1(ghcb);
control->exit_info_2 = ghcb_get_sw_exit_info_2(ghcb);

/* Clear the valid entries fields */
memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap));
}

static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
{
struct kvm_vcpu *vcpu;
struct ghcb *ghcb;
u64 exit_code = 0;

ghcb = svm->ghcb;

/* Only GHCB Usage code 0 is supported */
if (ghcb->ghcb_usage)
goto vmgexit_err;

/*
* Retrieve the exit code now even though is may not be marked valid
* as it could help with debugging.
*/
exit_code = ghcb_get_sw_exit_code(ghcb);

if (!ghcb_sw_exit_code_is_valid(ghcb) ||
!ghcb_sw_exit_info_1_is_valid(ghcb) ||
!ghcb_sw_exit_info_2_is_valid(ghcb))
goto vmgexit_err;

switch (ghcb_get_sw_exit_code(ghcb)) {
case SVM_EXIT_READ_DR7:
break;
case SVM_EXIT_WRITE_DR7:
if (!ghcb_rax_is_valid(ghcb))
goto vmgexit_err;
break;
case SVM_EXIT_RDTSC:
break;
case SVM_EXIT_RDPMC:
if (!ghcb_rcx_is_valid(ghcb))
goto vmgexit_err;
break;
case SVM_EXIT_CPUID:
if (!ghcb_rax_is_valid(ghcb) ||
!ghcb_rcx_is_valid(ghcb))
goto vmgexit_err;
if (ghcb_get_rax(ghcb) == 0xd)
if (!ghcb_xcr0_is_valid(ghcb))
goto vmgexit_err;
break;
case SVM_EXIT_INVD:
break;
case SVM_EXIT_IOIO:
if (!(ghcb_get_sw_exit_info_1(ghcb) & SVM_IOIO_TYPE_MASK))
if (!ghcb_rax_is_valid(ghcb))
goto vmgexit_err;
break;
case SVM_EXIT_MSR:
if (!ghcb_rcx_is_valid(ghcb))
goto vmgexit_err;
if (ghcb_get_sw_exit_info_1(ghcb)) {
if (!ghcb_rax_is_valid(ghcb) ||
!ghcb_rdx_is_valid(ghcb))
goto vmgexit_err;
}
break;
case SVM_EXIT_VMMCALL:
if (!ghcb_rax_is_valid(ghcb) ||
!ghcb_cpl_is_valid(ghcb))
goto vmgexit_err;
break;
case SVM_EXIT_RDTSCP:
break;
case SVM_EXIT_WBINVD:
break;
case SVM_EXIT_MONITOR:
if (!ghcb_rax_is_valid(ghcb) ||
!ghcb_rcx_is_valid(ghcb) ||
!ghcb_rdx_is_valid(ghcb))
goto vmgexit_err;
break;
case SVM_EXIT_MWAIT:
if (!ghcb_rax_is_valid(ghcb) ||
!ghcb_rcx_is_valid(ghcb))
goto vmgexit_err;
break;
case SVM_VMGEXIT_UNSUPPORTED_EVENT:
break;
default:
goto vmgexit_err;
}

return 0;

vmgexit_err:
vcpu = &svm->vcpu;

if (ghcb->ghcb_usage) {
vcpu_unimpl(vcpu, "vmgexit: ghcb usage %#x is not valid\n",
ghcb->ghcb_usage);
} else {
vcpu_unimpl(vcpu, "vmgexit: exit reason %#llx is not valid\n",
exit_code);
dump_ghcb(svm);
}

vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
vcpu->run->internal.ndata = 2;
vcpu->run->internal.data[0] = exit_code;
vcpu->run->internal.data[1] = vcpu->arch.last_vmentry_cpu;

return -EINVAL;
}

static void pre_sev_es_run(struct vcpu_svm *svm)
{
if (!svm->ghcb)
return;

sev_es_sync_to_ghcb(svm);

kvm_vcpu_unmap(&svm->vcpu, &svm->ghcb_map, true);
svm->ghcb = NULL;
}

void pre_sev_run(struct vcpu_svm *svm, int cpu)
{
struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
int asid = sev_get_asid(svm->vcpu.kvm);

/* Perform any SEV-ES pre-run actions */
pre_sev_es_run(svm);

/* Assign the asid allocated with this SEV guest */
svm->asid = asid;

Expand All @@ -1279,3 +1495,59 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu)
svm->vmcb->control.tlb_ctl = TLB_CONTROL_FLUSH_ASID;
vmcb_mark_dirty(svm->vmcb, VMCB_ASID);
}

static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
{
return -EINVAL;
}

int sev_handle_vmgexit(struct vcpu_svm *svm)
{
struct vmcb_control_area *control = &svm->vmcb->control;
u64 ghcb_gpa, exit_code;
struct ghcb *ghcb;
int ret;

/* Validate the GHCB */
ghcb_gpa = control->ghcb_gpa;
if (ghcb_gpa & GHCB_MSR_INFO_MASK)
return sev_handle_vmgexit_msr_protocol(svm);

if (!ghcb_gpa) {
vcpu_unimpl(&svm->vcpu, "vmgexit: GHCB gpa is not set\n");
return -EINVAL;
}

if (kvm_vcpu_map(&svm->vcpu, ghcb_gpa >> PAGE_SHIFT, &svm->ghcb_map)) {
/* Unable to map GHCB from guest */
vcpu_unimpl(&svm->vcpu, "vmgexit: error mapping GHCB [%#llx] from guest\n",
ghcb_gpa);
return -EINVAL;
}

svm->ghcb = svm->ghcb_map.hva;
ghcb = svm->ghcb_map.hva;

exit_code = ghcb_get_sw_exit_code(ghcb);

ret = sev_es_validate_vmgexit(svm);
if (ret)
return ret;

sev_es_sync_from_ghcb(svm);
ghcb_set_sw_exit_info_1(ghcb, 0);
ghcb_set_sw_exit_info_2(ghcb, 0);

ret = -EINVAL;
switch (exit_code) {
case SVM_VMGEXIT_UNSUPPORTED_EVENT:
vcpu_unimpl(&svm->vcpu,
"vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
control->exit_info_1, control->exit_info_2);
break;
default:
ret = svm_invoke_exit_handler(svm, exit_code);
}

return ret;
}
6 changes: 4 additions & 2 deletions arch/x86/kvm/svm/svm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -194,7 +194,7 @@ module_param(sev, int, 0444);
int sev_es = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
module_param(sev_es, int, 0444);

static bool __read_mostly dump_invalid_vmcb = 0;
bool __read_mostly dump_invalid_vmcb;
module_param(dump_invalid_vmcb, bool, 0644);

static u8 rsm_ins_bytes[] = "\x0f\xaa";
Expand Down Expand Up @@ -2977,6 +2977,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
[SVM_EXIT_RSM] = rsm_interception,
[SVM_EXIT_AVIC_INCOMPLETE_IPI] = avic_incomplete_ipi_interception,
[SVM_EXIT_AVIC_UNACCELERATED_ACCESS] = avic_unaccelerated_access_interception,
[SVM_EXIT_VMGEXIT] = sev_handle_vmgexit,
};

static void dump_vmcb(struct kvm_vcpu *vcpu)
Expand Down Expand Up @@ -3018,6 +3019,7 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
pr_err("%-20s%lld\n", "nested_ctl:", control->nested_ctl);
pr_err("%-20s%016llx\n", "nested_cr3:", control->nested_cr3);
pr_err("%-20s%016llx\n", "avic_vapic_bar:", control->avic_vapic_bar);
pr_err("%-20s%016llx\n", "ghcb:", control->ghcb_gpa);
pr_err("%-20s%08x\n", "event_inj:", control->event_inj);
pr_err("%-20s%08x\n", "event_inj_err:", control->event_inj_err);
pr_err("%-20s%lld\n", "virt_ext:", control->virt_ext);
Expand Down Expand Up @@ -3114,7 +3116,7 @@ static int svm_handle_invalid_exit(struct kvm_vcpu *vcpu, u64 exit_code)
return -EINVAL;
}

static int svm_invoke_exit_handler(struct vcpu_svm *svm, u64 exit_code)
int svm_invoke_exit_handler(struct vcpu_svm *svm, u64 exit_code)
{
if (svm_handle_invalid_exit(&svm->vcpu, exit_code))
return 0;
Expand Down
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