On Mon, Aug 27, 2012 at 01:22:55PM -0700, Avi Kivity wrote:
> On 08/26/2012 10:04 AM, Marcelo Tosatti wrote:
> > On Thu, Aug 23, 2012 at 05:14:27AM -0300, Marcelo Tosatti wrote:
> > > On Sun, Aug 19, 2012 at 12:32:36PM +0300, Avi Kivity wrote:
> > > > On 08/17/2012 08:29 PM, Marcelo Tosatti wrote:
> > > > > On Thu, Aug 16, 2012 at 05:54:49PM +0300, Avi Kivity wrote:
> > > > >> Instead of populating the the entire register file, read in registers
> > > > >> as they are accessed, and write back only the modified ones. This
> > > > >> saves a VMREAD and VMWRITE on Intel (for rsp, since it is not usually
> > > > >> used during emulation), and a two 128-byte copies for the registers.
> > > > >>
> > > > >
> > > > >> @@ -2715,14 +2764,17 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
> > > > >> {
> > > > >> int rc;
> > > > >>
> > > > >> + invalidate_registers(ctxt);
> > > > >> ctxt->_eip = ctxt->eip;
> > > > >> ctxt->dst.type = OP_NONE;
> > > > >>
> > > > >> rc = emulator_do_task_switch(ctxt, tss_selector, idt_index, reason,
> > > > >> has_error_code, error_code);
> > > > >>
> > > > >> - if (rc == X86EMUL_CONTINUE)
> > > > >> + if (rc == X86EMUL_CONTINUE) {
> > > > >> ctxt->eip = ctxt->_eip;
> > > > >> + writeback_registers(ctxt);
> > > > >> + }
> > > > >>
> > > > >> return (rc == X86EMUL_UNHANDLEABLE) ? EMULATION_FAILED : EMULATION_OK;
> > > > >> }
> > > > >
> > > > >
> > > > > No clear point when emulator register cache is active, when it is
> > > > > not (AFAICS this patch does not invalidate registers on emulation start
> > > > > (the above being one of the exceptions) does not clear valid bit on
> > > > > writeback-to-vcpu-cache on emulation exit).
> > > >
> > > > It is cleared when emulation starts. For the non-insn-emulation entry
> > > > points, there is an explicit invalidate. For the emulation entry point,
> > > > there is a memset() that clears everything up to _regs, which includes
> > > > the cache. This discrepancy isn't nice, but it preexists. I don't know
> > > > whether we should decompose the memset() or not, it is rather efficient.
> > > >
> > > > >
> > > > > Concern is that emulator can start with cached registers marked as valid
> > > > > but in fact are invalid from previous emulation round.
> > > > >
> > > > > Maybe move invalidate() to init_emulate_ctxt?
> > > > >
> > > >
> > > > See the memset() in init_decode_cache().
> > >
> > > Right. Applied, thanks.
> >
> > Actually, had to revert because autotest was failing.
> >
>
> Was it failing because of this patch? Or what?
No, due to lack of stack size fix.
With the fix, it rejects. About to merge the big real mode
patchset, so its not a bad idea to wait for that before
resending.
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
