x86/hvm: Corrections to RDTSCP intercept handling

For both VT-x and SVM, the RDTSCP intercept will trigger if the pipeline
supports the instruction, but the guest may not have RDTSCP in its featureset.
Bring the vmexit handlers in line with the main emulator behaviour by
optionally handing back #UD.

Next on the AMD side, if RDTSCP actually ends up being intercepted on a debug
build or first-gen SVM hardware which lacks NRIP, we first update regs->rcx,
then call __get_instruction_length() asking for RDTSC.  As the two
instructions are different (and indeed, different lengths!),
__get_instruction_length_from_list() fails and hands back a #GP fault.

This can demonstrated by putting a guest into tsc_mode="always emulate" and
executing an RDTSCP instruction:

  (d1) --- Xen Test Framework ---
  (d1) Environment: HVM 64bit (Long mode 4 levels)
  (d1) Test rdtscp
  (d1) TSC mode 1
  (XEN) emulate.c:147:d1v0 __get_instruction_length: Mismatch between expected and actual instruction:
  (XEN) emulate.c:152:d1v0   insn_index 8, opcode 0xf0031 modrm 0
  (XEN) emulate.c:154:d1v0   rip 0x10475f, nextrip 0x104762, len 3
  (XEN) SVM insn len emulation failed (1): d1v0 64bit @ 0008:0010475f -> 0f 01 f9 0f 31 5b 31 ff 31 c0 e9 c2 db ff ff 00
  (d1) ******************************
  (d1) PANIC: Unhandled exception at 0008:000000000010475f
  (d1) Vec 13 #GP[0000]
  (d1) ******************************

First, teach __get_instruction_length() to cope with RDTSCP, and improve
svm_vmexit_do_rdtsc() to ask for the correct instruction.  Move the regs->rcx
adjustment into this function to ensure it gets done after we are done
potentially raising faults.

Reported-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Brian Woods <brian.woods@amd.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

diff --git a/xen/arch/x86/hvm/svm/emulate.c b/xen/arch/x86/hvm/svm/emulate.c
index 3d04af0ea93fa37a98d92cf45dc5e37873a5873d..4abeab865537f13c92b3c4847cff3b081931fc68 100644 (file)
--- a/xen/arch/x86/hvm/svm/emulate.c
+++ b/xen/arch/x86/hvm/svm/emulate.c
@@ -75,6 +75,7 @@ static const struct {
     [INSTR_STGI]    = { X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 4) },
     [INSTR_CLGI]    = { X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 5) },
     [INSTR_INVLPGA] = { X86EMUL_OPC(0x0f, 0x01), MODRM(3, 3, 7) },
+    [INSTR_RDTSCP]  = { X86EMUL_OPC(0x0f, 0x01), MODRM(3, 7, 1) },
     [INSTR_INVD]    = { X86EMUL_OPC(0x0f, 0x08) },
     [INSTR_WBINVD]  = { X86EMUL_OPC(0x0f, 0x09) },
     [INSTR_WRMSR]   = { X86EMUL_OPC(0x0f, 0x30) },

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 40937bfa4743227f0c5345d8a2a5eebe9ebcd84f..9464394b0d44c6f61cc5a3322a5c41e1f756ba50 100644 (file)
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2279,14 +2279,28 @@ static void svm_vmexit_do_hlt(struct vmcb_struct *vmcb,
     hvm_hlt(regs->eflags);
 }
 
-static void svm_vmexit_do_rdtsc(struct cpu_user_regs *regs)
+static void svm_vmexit_do_rdtsc(struct cpu_user_regs *regs, bool rdtscp)
 {
+    struct vcpu *curr = current;
+    const struct domain *currd = curr->domain;
+    enum instruction_index insn = rdtscp ? INSTR_RDTSCP : INSTR_RDTSC;
     unsigned int inst_len;
 
-    if ( (inst_len = __get_instruction_length(current, INSTR_RDTSC)) == 0 )
+    if ( rdtscp && !currd->arch.cpuid->extd.rdtscp &&
+         currd->arch.tsc_mode != TSC_MODE_PVRDTSCP )
+    {
+        hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
         return;
+    }
+
+    if ( (inst_len = __get_instruction_length(curr, insn)) == 0 )
+        return;
+
     __update_guest_eip(regs, inst_len);
 
+    if ( rdtscp )
+        regs->rcx = hvm_msr_tsc_aux(curr);
+
     hvm_rdtsc_intercept(regs);
 }
 
@@ -2968,10 +2982,8 @@ void svm_vmexit_handler(struct cpu_user_regs *regs)
         break;
 
     case VMEXIT_RDTSCP:
-        regs->rcx = hvm_msr_tsc_aux(v);
-        /* fall through */
     case VMEXIT_RDTSC:
-        svm_vmexit_do_rdtsc(regs);
+        svm_vmexit_do_rdtsc(regs, exit_reason == VMEXIT_RDTSCP);
         break;
 
     case VMEXIT_MONITOR:

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 7f77d1fd283a4486d644b40b1c8be795b724216f..2166b0dfe4369ecbb611739840dc9df2fff348cb 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3589,6 +3589,7 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
     unsigned long exit_qualification, exit_reason, idtv_info, intr_info = 0;
     unsigned int vector = 0, mode;
     struct vcpu *v = current;
+    struct domain *currd = v->domain;
 
     __vmread(GUEST_RIP,    &regs->rip);
     __vmread(GUEST_RSP,    &regs->rsp);
@@ -3956,6 +3957,13 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
         vmx_invlpg_intercept(exit_qualification);
         break;
     case EXIT_REASON_RDTSCP:
+        if ( !currd->arch.cpuid->extd.rdtscp &&
+             currd->arch.tsc_mode != TSC_MODE_PVRDTSCP )
+        {
+            hvm_inject_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC);
+            break;
+        }
+
         regs->rcx = hvm_msr_tsc_aux(v);
         /* fall through */
     case EXIT_REASON_RDTSC:

diff --git a/xen/include/asm-x86/hvm/svm/emulate.h b/xen/include/asm-x86/hvm/svm/emulate.h
index 3de8236301dfba2f0b747ae7ffd220ed3b176af7..ca92abbe28c5c69bb9edd3cf2b60c0b54ba1b83d 100644 (file)
--- a/xen/include/asm-x86/hvm/svm/emulate.h
+++ b/xen/include/asm-x86/hvm/svm/emulate.h
@@ -30,6 +30,7 @@ enum instruction_index {
     INSTR_HLT,
     INSTR_INT3,
     INSTR_RDTSC,
+    INSTR_RDTSCP,
     INSTR_PAUSE,
     INSTR_XSETBV,
     INSTR_VMRUN,