On 12/07/2010 12:59 PM, Andre Przywara wrote:
In case of a nested page fault or an intercepted #PF newer SVM
implementations provide a copy of the faulting instruction bytes
in the VMCB.
Use these bytes to feed the instruction emulator and avoid the costly
guest instruction fetch in this case.
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index cfbcbfa..3e3a67e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -586,6 +586,9 @@ struct kvm_x86_ops {
void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
+
+ int (*prefetch_instruction)(struct kvm_vcpu *vcpu);
+
const struct trace_print_flags *exit_reasons_str;
};
How about adding a byte array/len parameter to x86_decode_insn()? It
could be used to prefill the buffer instead of invoking a callback.
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 6366735..abff8ff 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -525,6 +525,7 @@ static int do_insn_fetch(struct x86_emulate_ctxt *ctxt,
/* x86 instructions are limited to 15 bytes. */
if (eip + size - ctxt->eip> 15)
return X86EMUL_UNHANDLEABLE;
+ kvm_x86_ops->prefetch_instruction(ctxt->vcpu);
Even with the callback, this belongs in x86_decode_insn(), not on every
fetch.
while (size--) {
rc = do_fetch_insn_byte(ctxt, ops, eip++, dest++);
if (rc != X86EMUL_CONTINUE)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 3cf2cef..ed94e9a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -464,6 +464,24 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu)
svm_set_interrupt_shadow(vcpu, 0);
}
+static int prefetch_instruction(struct kvm_vcpu *vcpu)
svm_prefetch_instruction()
+{
+ struct vcpu_svm *svm = to_svm(vcpu);
+ uint8_t len;
+ struct fetch_cache *fetch;
+
+ len = svm->vmcb->control.insn_len& 0x0F;
+ if (len == 0)
+ return 1;
+
+ fetch =&svm->vcpu.arch.emulate_ctxt.decode.fetch;
+ fetch->start = kvm_rip_read(&svm->vcpu);
+ fetch->end = fetch->start + len;
+ memcpy(fetch->data, svm->vmcb->control.insn_bytes, len);
+
+ return 0;
+}
svm code shouldn't reach in so deep into the emulator privates.
--
error compiling committee.c: too many arguments to function
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