[PATCH v3 2/2] KVM: X86: Kill off ctxt->ud

From: Wanpeng Li
Date: Thu May 27 2021 - 01:02:22 EST


From: Wanpeng Li <wanpengli@xxxxxxxxxxx>

ctxt->ud is consumed only by x86_decode_insn(), we can kill it off by passing
emulation_type to x86_decode_insn() and dropping ctxt->ud altogether. Tracking
that info in ctxt for literally one call is silly.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 5 +++--
arch/x86/kvm/kvm_emulate.h | 3 +--
arch/x86/kvm/x86.c | 4 +---
3 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 8a0ccdb..5e5de05 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5111,7 +5111,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
return rc;
}

-int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
+int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int emulation_type)
{
int rc = X86EMUL_CONTINUE;
int mode = ctxt->mode;
@@ -5322,7 +5322,8 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)

ctxt->execute = opcode.u.execute;

- if (unlikely(ctxt->ud) && likely(!(ctxt->d & EmulateOnUD)))
+ if (unlikely(emulation_type & EMULTYPE_TRAP_UD) &&
+ likely(!(ctxt->d & EmulateOnUD)))
return EMULATION_FAILED;

if (unlikely(ctxt->d &
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index f016838..3e870bf 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -314,7 +314,6 @@ struct x86_emulate_ctxt {
int interruptibility;

bool perm_ok; /* do not check permissions if true */
- bool ud; /* inject an #UD if host doesn't support insn */
bool tf; /* TF value before instruction (after for syscall/sysret) */

bool have_exception;
@@ -491,7 +490,7 @@ enum x86_intercept {
#define X86EMUL_MODE_HOST X86EMUL_MODE_PROT64
#endif

-int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len);
+int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int emulation_type);
bool x86_page_table_writing_insn(struct x86_emulate_ctxt *ctxt);
#define EMULATION_FAILED -1
#define EMULATION_OK 0
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ae47b19..d752345 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7231,8 +7231,6 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
ctxt->exception.vector = -1;
ctxt->perm_ok = false;

- ctxt->ud = emulation_type & EMULTYPE_TRAP_UD;
-
init_decode_cache(ctxt);
vcpu->arch.emulate_regs_need_sync_from_vcpu = false;
}
@@ -7568,7 +7566,7 @@ int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type,
kvm_vcpu_check_breakpoint(vcpu, &r))
return r;

- r = x86_decode_insn(ctxt, insn, insn_len);
+ r = x86_decode_insn(ctxt, insn, insn_len, emulation_type);

trace_kvm_emulate_insn_start(vcpu);
++vcpu->stat.insn_emulation;
--
2.7.4