Re: [PATCH v2 02/11] KVM: x86: emulator: introduce update_emulation_mode

Sean Christopherson
2022-07-20T23:45:05Z

On Tue, Jun 21, 2022, Maxim Levitsky wrote:
> +static inline int update_emulation_mode(struct x86_emulate_ctxt *ctxt)

Maybe emulator_recalc_and_set_mode()? It took me a second to understand that
"update" also involves determining the "new" mode, e.g. I was trying to figure
out where @mode was :-)

> +{
> + u64 efer;
> + struct desc_struct cs;
> + u16 selector;
> + u32 base3;
> +
> + ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
> +
> + if (!ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) {
> + /* Real mode. cpu must not have long mode active */
> + if (efer & EFER_LMA)
> + return X86EMUL_UNHANDLEABLE;

If we hit this, is there any hope of X86EMUL_UNHANDLEABLE doing the right thing?
Ah, SMM and the ability to swizzle SMRAM state. Bummer. I was hoping we could
just bug the VM.

> + ctxt->mode = X86EMUL_MODE_REAL;
> + return X86EMUL_CONTINUE;
> + }