[Xen-devel] Re: [Patch 1/3] Refining Xsave/Xrestore support - Version 3

[Haitao Shan <maillists.shan@xxxxxxxxx>]

Updated...Thanks for Jan's careful review, indeed.

Shan Haitao

2010/11/2 Jan Beulich <JBeulich@xxxxxxxxxx>:
>>>> On 02.11.10 at 04:47, Haitao Shan <maillists.shan@xxxxxxxxx> wrote:
>>@@ -1796,7 +1796,10 @@ static int emulate_privileged_op(struct
>>
>>     /* REX prefix. */
>>     if ( rex & 8 ) /* REX.W */
>>+    {
>>+        opsize_prefix = 0; /* 66H is ignored according to SDM 2A */
>
> This I'm sure isn't correct: The 0x66 prefix is being ignored as an
> operand size override here, but REX.W has no interaction with
> 0x66 when the latter is used as an opcode extension selector.
>
> Specifically in the case of xsetbv the manual clearly states
>
> #UD     If CPUID.01H:ECX.XSAVE[bit 26] = 0.
>        If CR4.OSXSAVE[bit 18] = 0.
>        If the LOCK prefix is used.
>        If 66H, F3H or F2H prefix is used.
>
>>@@ -2051,13 +2054,48 @@ static int emulate_privileged_op(struct
>>         goto fail;
>>     switch ( opcode )
>>     {
>>-    case 0x1: /* RDTSCP */
>>-        if ( (v->arch.guest_context.ctrlreg[4] & X86_CR4_TSD) &&
>>-             !guest_kernel_mode(v, regs) )
>>+    case 0x1: /* RDTSCP and XSETBV */
>>+        switch ( insn_fetch(u8, code_base, eip, code_limit) )
>>+        {
>>+        case 0xf9: /* RDTSCP */
>>+            if ( (v->arch.guest_context.ctrlreg[4] & X86_CR4_TSD) &&
>>+                 !guest_kernel_mode(v, regs) )
>>+                goto fail;
>>+            pv_soft_rdtsc(v, regs, 1);
>>+            break;
>>+        case 0xd1: /* XSETBV */
>>+        {
>>+            u64 new_xfeature = (u32)regs->eax | ((u64)regs->edx << 32);
>>+
>>+            if ( lock || rep_prefix || opsize_prefix
>>+                 || !(v->arch.guest_context.ctrlreg[4] & X86_CR4_OSXSAVE) )
>>+            {
>>+                do_guest_trap(TRAP_invalid_op, regs, 0);
>>+                break;
>
> I think you need to "goto skip" or "return EXCRET_fault_fixed" here,
> to avoid executing instruction_done().
>
> Jan
>
>

Attachment: pv-xsave.patch
Description: Binary data

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