[RFC v1 7/7] x86/svm: Use the emulator path for VMEXIT_CR*

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

If the processor has provided extra information, use that to accelerate
the emulator path.

The hvmemul_{read,write}_cr callbacks are used for consistent behaviour
between emulated and fast paths.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
 xen/arch/x86/hvm/emulate.c             | 11 ++++++++++
 xen/arch/x86/hvm/svm/svm.c             | 28 +++++++++-----------------
 xen/arch/x86/include/asm/hvm/emulate.h |  7 +++++++
 xen/arch/x86/include/asm/hvm/hvm.h     |  2 ++
 4 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 471c032c1e9c..0f7507575884 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2804,6 +2804,17 @@ static int _hvm_emulate_one(struct hvm_emulate_ctxt 
*hvmemul_ctxt,
             hvmemul_ctxt->ctxt.retire.hlt = true;
             rc = X86EMUL_OKAY;
             break;
+        case INSTR_MOV_FROM_CR:
+        case INSTR_MOV_TO_CR:
+        {
+            unsigned long *val = decode_gpr(regs, hvmemul_ctxt->u.cr.gp);
+
+            if ( hvmemul_ctxt->insn == INSTR_MOV_TO_CR )
+                rc = hvmemul_write_cr(hvmemul_ctxt->u.cr.cr, *val, 
&hvmemul_ctxt->ctxt);
+            else
+                rc = hvmemul_read_cr(hvmemul_ctxt->u.cr.cr, val, 
&hvmemul_ctxt->ctxt);
+            break;
+        }
 
         default:
             ASSERT_UNREACHABLE();
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 2d6022d6238c..3ba852f52666 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1625,22 +1625,6 @@ static void svm_do_nested_pgfault(struct vcpu *v,
     domain_crash(v->domain);
 }
 
-static void svm_vmexit_do_cr_access(
-    struct vmcb_struct *vmcb, struct cpu_user_regs *regs)
-{
-    int gp, cr, dir, rc;
-
-    cr = vmcb->exitcode - VMEXIT_CR0_READ;
-    dir = (cr > 15);
-    cr &= 0xf;
-    gp = vmcb->ei.mov_cr.gpr;
-
-    rc = dir ? hvm_mov_to_cr(cr, gp) : hvm_mov_from_cr(cr, gp);
-
-    if ( rc == X86EMUL_OKAY )
-        __update_guest_eip(regs, vmcb->nextrip - vmcb->rip);
-}
-
 static void svm_dr_access(struct vcpu *v, struct cpu_user_regs *regs)
 {
     struct vmcb_struct *vmcb = vcpu_nestedhvm(v).nv_n1vmcx;
@@ -2869,10 +2853,16 @@ void asmlinkage svm_vmexit_handler(void)
 
     case VMEXIT_CR0_READ ... VMEXIT_CR15_READ:
     case VMEXIT_CR0_WRITE ... VMEXIT_CR15_WRITE:
+        hvm_emulate_init_once(&ctxt, x86_insn_is_cr_access, "CR access", regs);
+
         if ( cpu_has_svm_decode && vmcb->ei.mov_cr.mov_insn )
-            svm_vmexit_do_cr_access(vmcb, regs);
-        else if ( !hvm_emulate_one_insn(x86_insn_is_cr_access, "CR access") )
-            hvm_inject_hw_exception(X86_EXC_GP, 0);
+        {
+            ctxt.u.cr.cr = vmcb->exitcode - VMEXIT_CR0_READ;
+            ctxt.insn = (ctxt.u.cr.cr > 15) ? INSTR_MOV_TO_CR : 
INSTR_MOV_FROM_CR;
+            ctxt.u.cr.cr = ctxt.u.cr.cr & 0xf;
+            ctxt.u.cr.gp = vmcb->ei.mov_cr.gpr;
+        }
+        svm_emulate_one(&ctxt);
         break;
 
     case VMEXIT_INVLPG:
diff --git a/xen/arch/x86/include/asm/hvm/emulate.h 
b/xen/arch/x86/include/asm/hvm/emulate.h
index 1e626f8af8f2..3661ca28d6f4 100644
--- a/xen/arch/x86/include/asm/hvm/emulate.h
+++ b/xen/arch/x86/include/asm/hvm/emulate.h
@@ -56,6 +56,13 @@ struct hvm_emulate_ctxt {
 
     unsigned int insn;
     unsigned int insn_len;
+
+    union {
+        struct {
+            int cr;
+            int gp;
+        } cr;
+    } u;
 };
 
 enum emul_kind {
diff --git a/xen/arch/x86/include/asm/hvm/hvm.h 
b/xen/arch/x86/include/asm/hvm/hvm.h
index a9b64814ca71..7732217e279a 100644
--- a/xen/arch/x86/include/asm/hvm/hvm.h
+++ b/xen/arch/x86/include/asm/hvm/hvm.h
@@ -879,6 +879,8 @@ static inline void hvm_sync_pir_to_irr(struct vcpu *v)
 #define INSTR_RDTSC      INSTR_ENC(X86EMUL_OPC(0x0f, 0x31), 0)
 #define INSTR_RDMSR      INSTR_ENC(X86EMUL_OPC(0x0f, 0x32), 0)
 #define INSTR_CPUID      INSTR_ENC(X86EMUL_OPC(0x0f, 0xa2), 0)
+#define INSTR_MOV_FROM_CR INSTR_ENC(X86EMUL_OPC(0x0f, 0x20), 0)
+#define INSTR_MOV_TO_CR  INSTR_ENC(X86EMUL_OPC(0x0f, 0x22), 0)
 
 #else  /* CONFIG_HVM */
 
-- 
2.53.0