2017-05-30 12:15+0200, Paolo Bonzini:
> On 30/05/2017 00:48, Nick Desaulniers wrote:
>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>> @@ -3985,57 +3985,45 @@ static int em_fxsave(struct x86_emulate_ctxt *ctxt)
>> static int em_fxrstor(struct x86_emulate_ctxt *ctxt)
>> {
>> struct fxregs_state fx_state;
>> int rc;
>> + unsigned int size;
>>
>> rc = check_fxsr(ctxt);
>> if (rc != X86EMUL_CONTINUE)
>> return rc;
>>
>> - rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state, 512);
>> - if (rc != X86EMUL_CONTINUE)
>> - return rc;
>> + ctxt->ops->get_fpu(ctxt);
>> +
>> + if (ctxt->mode < X86EMUL_MODE_PROT64) {
>> + rc = asm_safe("fxsave %[fx]", , [fx] "+m"(fx_state));
>> + if (rc != X86EMUL_CONTINUE)
>> + return rc;
Please call ctxt->ops->put_fpu() before returning.
(Don't be afraid to use 'goto', the will likely be more of them.)
>> + /*
>> + * Hardware doesn't save and restore XMM 0-7 without
>> + * CR4.OSFXSR, but does save and restore MXCSR.
>> + */
>> + if (ctxt->ops->get_cr(ctxt, 4) & X86_CR4_OSFXSR)
>> + size = offsetof(struct fxregs_state, xmm_space[8]);
This should be the size of first 8 XMM registers, but xmm_space is of
type u32, so the correct size is
xmm_space[8 * 16/sizeof(*fx_state.xmm_space)].
Adding a separate function to compute the size and call it from
em_fxrstor and em_fxsave would make sense at this point.
>> + else
>> + size = offsetof(struct fxregs_state, xmm_space[0]);
>> + rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state,
>> + size);
>> + if (rc != X86EMUL_CONTINUE)
>> + return rc;
>> + } else if (ctxt->mode == X86EMUL_MODE_PROT64) {
>> + size = offsetof(struct fxregs_state, xmm_space[16]);
>> + rc = segmented_read_std(ctxt, ctxt->memop.addr.mem, &fx_state,
>> + size);
>> + if (rc != X86EMUL_CONTINUE)
>> + return rc;
>> + }
>
> You can just remove the "if (ctxt->mode == X86EMUL_MODE_PROT64)". This
> way, the call of segmented_read_std and the "if (rc !=
> X86EMUL_CONTINUE)" can move outside the conditional.
Good idea. check_fxsr() doesn't allow X86EMUL_MODE_PROT64 and the
condition was an artefact from older iterations.
I'll refresh the kvm-unit-test ([kvm-unit-tests PATCH] x86: realmode:
add FXSR tests).
