KVM: SVM: copy instruction bytes from VMCB

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.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

3 files changed, 9 insertions, 6 deletions

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index bf70ecea3974..8e37deb1eb38 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -265,7 +265,7 @@ struct x86_emulate_ctxt {
 #define X86EMUL_MODE_HOST X86EMUL_MODE_PROT64
 #endif
 
-int x86_decode_insn(struct x86_emulate_ctxt *ctxt);
+int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len);
 #define EMULATION_FAILED -1
 #define EMULATION_OK 0
 #define EMULATION_RESTART 1
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index de00b6026b76..6268f6ce6434 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -634,13 +634,13 @@ enum emulation_result {
 #define EMULTYPE_NO_DECODE          (1 << 0)
 #define EMULTYPE_TRAP_UD            (1 << 1)
 #define EMULTYPE_SKIP               (1 << 2)
-int x86_emulate_instruction(struct kvm_vcpu *vcpu,
-                        unsigned long cr2, int emulation_type);
+int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
+                            int emulation_type, void *insn, int insn_len);
 
 static inline int emulate_instruction(struct kvm_vcpu *vcpu,
                         int emulation_type)
 {
-        return x86_emulate_instruction(vcpu, 0, emulation_type);
+        return x86_emulate_instruction(vcpu, 0, emulation_type, NULL, 0);
 }
 
 void realmode_lgdt(struct kvm_vcpu *vcpu, u16 size, unsigned long address);
@@ -721,7 +721,8 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu);
 
 int kvm_fix_hypercall(struct kvm_vcpu *vcpu);
 
-int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t gva, u32 error_code);
+int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t gva, u32 error_code,
+                       void *insn, int insn_len);
 void kvm_mmu_invlpg(struct kvm_vcpu *vcpu, gva_t gva);
 
 void kvm_enable_tdp(void);
diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index f0ffb8184089..f2b83bc7d784 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -83,7 +83,9 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
         u32 clean;
         u32 reserved_5;
         u64 next_rip;
-        u8 reserved_6[816];
+        u8 insn_len;
+        u8 insn_bytes[15];
+        u8 reserved_6[800];
 };