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KVM: x86: Refactor can_emulate_instruction() return to be more expressive

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Refactor and rename can_emulate_instruction() to allow vendor code to
return more than true/false, e.g. to explicitly differentiate between
"retry", "fault", and "unhandleable".  For now, just do the plumbing, a
future patch will expand SVM's implementation to signal outright failure
if KVM attempts EMULTYPE_SKIP on an SEV guest.

No functional change intended (or rather, none that are visible to the
guest or userspace).

Link: https://lore.kernel.org/r/20230825013621.2845700-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2023-08-24 18:36:20 -07:00
parent bc3d7c5570
commit aeb904f6b9
5 changed files with 35 additions and 29 deletions
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2
arch/x86/include/asm/kvm-x86-ops.h
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@ -126,7 +126,7 @@ KVM_X86_OP_OPTIONAL(vm_copy_enc_context_from)
KVM_X86_OP_OPTIONAL(vm_move_enc_context_from)
KVM_X86_OP_OPTIONAL(guest_memory_reclaimed)
KVM_X86_OP(get_msr_feature)
KVM_X86_OP(can_emulate_instruction)
KVM_X86_OP(check_emulate_instruction)
KVM_X86_OP(apic_init_signal_blocked)
KVM_X86_OP_OPTIONAL(enable_l2_tlb_flush)
KVM_X86_OP_OPTIONAL(migrate_timers)

4
arch/x86/include/asm/kvm_host.h
View File

@ -1734,8 +1734,8 @@ struct kvm_x86_ops {
int (*get_msr_feature)(struct kvm_msr_entry *entry);
bool (*can_emulate_instruction)(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len);
int (*check_emulate_instruction)(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len);
bool (*apic_init_signal_blocked)(struct kvm_vcpu *vcpu);
int (*enable_l2_tlb_flush)(struct kvm_vcpu *vcpu);

31
arch/x86/kvm/svm/svm.c
View File

@ -364,8 +364,8 @@ static void svm_set_interrupt_shadow(struct kvm_vcpu *vcpu, int mask)
svm->vmcb->control.int_state |= SVM_INTERRUPT_SHADOW_MASK;
}
static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len);
static int svm_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len);
static int __svm_skip_emulated_instruction(struct kvm_vcpu *vcpu,
bool commit_side_effects)
@ -391,7 +391,7 @@ static int __svm_skip_emulated_instruction(struct kvm_vcpu *vcpu,
* right thing and treats "can't emulate" as outright failure
* for EMULTYPE_SKIP.
*/
if (!svm_can_emulate_instruction(vcpu, EMULTYPE_SKIP, NULL, 0))
if (svm_check_emulate_instruction(vcpu, EMULTYPE_SKIP, NULL, 0) != X86EMUL_CONTINUE)
return 0;
if (unlikely(!commit_side_effects))
@ -4727,15 +4727,15 @@ static void svm_enable_smi_window(struct kvm_vcpu *vcpu)
}
#endif
static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len)
static int svm_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len)
{
bool smep, smap, is_user;
u64 error_code;
/* Emulation is always possible when KVM has access to all guest state. */
if (!sev_guest(vcpu->kvm))
return true;
return X86EMUL_CONTINUE;
/* #UD and #GP should never be intercepted for SEV guests. */
WARN_ON_ONCE(emul_type & (EMULTYPE_TRAP_UD |
@ -4747,14 +4747,14 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
* to guest register state.
*/
if (sev_es_guest(vcpu->kvm))
return false;
return X86EMUL_RETRY_INSTR;
/*
* Emulation is possible if the instruction is already decoded, e.g.
* when completing I/O after returning from userspace.
*/
if (emul_type & EMULTYPE_NO_DECODE)
return true;
return X86EMUL_CONTINUE;
/*
* Emulation is possible for SEV guests if and only if a prefilled
@ -4780,9 +4780,11 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
* success (and in practice it will work the vast majority of the time).
*/
if (unlikely(!insn)) {
if (!(emul_type & EMULTYPE_SKIP))
kvm_queue_exception(vcpu, UD_VECTOR);
return false;
if (emul_type & EMULTYPE_SKIP)
return X86EMUL_RETRY_INSTR;
kvm_queue_exception(vcpu, UD_VECTOR);
return X86EMUL_PROPAGATE_FAULT;
}
/*
@ -4793,7 +4795,7 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
* table used to translate CS:RIP resides in emulated MMIO.
*/
if (likely(insn_len))
return true;
return X86EMUL_CONTINUE;
/*
* Detect and workaround Errata 1096 Fam_17h_00_0Fh.
@ -4851,6 +4853,7 @@ static bool svm_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
kvm_inject_gp(vcpu, 0);
else
kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
return X86EMUL_PROPAGATE_FAULT;
}
resume_guest:
@ -4868,7 +4871,7 @@ resume_guest:
* doesn't explicitly define "ignored", i.e. doing nothing and letting
* the guest spin is technically "ignoring" the access.
*/
return false;
return X86EMUL_RETRY_INSTR;
}
static bool svm_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
@ -5028,7 +5031,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.vm_copy_enc_context_from = sev_vm_copy_enc_context_from,
.vm_move_enc_context_from = sev_vm_move_enc_context_from,
.can_emulate_instruction = svm_can_emulate_instruction,
.check_emulate_instruction = svm_check_emulate_instruction,
.apic_init_signal_blocked = svm_apic_init_signal_blocked,

12
arch/x86/kvm/vmx/vmx.c
View File

@ -1657,8 +1657,8 @@ static int vmx_rtit_ctl_check(struct kvm_vcpu *vcpu, u64 data)
return 0;
}
static bool vmx_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len)
static int vmx_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len)
{
/*
* Emulation of instructions in SGX enclaves is impossible as RIP does
@ -1669,9 +1669,9 @@ static bool vmx_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
*/
if (to_vmx(vcpu)->exit_reason.enclave_mode) {
kvm_queue_exception(vcpu, UD_VECTOR);
return false;
return X86EMUL_PROPAGATE_FAULT;
}
return true;
return X86EMUL_CONTINUE;
}
static int skip_emulated_instruction(struct kvm_vcpu *vcpu)
@ -5792,7 +5792,7 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
{
gpa_t gpa;
if (!vmx_can_emulate_instruction(vcpu, EMULTYPE_PF, NULL, 0))
if (vmx_check_emulate_instruction(vcpu, EMULTYPE_PF, NULL, 0))
return 1;
/*
@ -8341,7 +8341,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
.enable_smi_window = vmx_enable_smi_window,
#endif
.can_emulate_instruction = vmx_can_emulate_instruction,
.check_emulate_instruction = vmx_check_emulate_instruction,
.apic_init_signal_blocked = vmx_apic_init_signal_blocked,
.migrate_timers = vmx_migrate_timers,

15
arch/x86/kvm/x86.c
View File

@ -7474,11 +7474,11 @@ int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, gva_t addr, void *val,
}
EXPORT_SYMBOL_GPL(kvm_write_guest_virt_system);
static int kvm_can_emulate_insn(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len)
static int kvm_check_emulate_insn(struct kvm_vcpu *vcpu, int emul_type,
void *insn, int insn_len)
{
return static_call(kvm_x86_can_emulate_instruction)(vcpu, emul_type,
insn, insn_len);
return static_call(kvm_x86_check_emulate_instruction)(vcpu, emul_type,
insn, insn_len);
}
int handle_ud(struct kvm_vcpu *vcpu)
@ -7488,8 +7488,10 @@ int handle_ud(struct kvm_vcpu *vcpu)
int emul_type = EMULTYPE_TRAP_UD;
char sig[5]; /* ud2; .ascii "kvm" */
struct x86_exception e;
int r;
if (unlikely(!kvm_can_emulate_insn(vcpu, emul_type, NULL, 0)))
r = kvm_check_emulate_insn(vcpu, emul_type, NULL, 0);
if (r != X86EMUL_CONTINUE)
return 1;
if (fep_flags &&
@ -8871,7 +8873,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
bool writeback = true;
if (unlikely(!kvm_can_emulate_insn(vcpu, emulation_type, insn, insn_len)))
r = kvm_check_emulate_insn(vcpu, emulation_type, insn, insn_len);
if (r != X86EMUL_CONTINUE)
return 1;
vcpu->arch.l1tf_flush_l1d = true;