On 08/27/2012 01:22 PM, 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?
>
I see, the rsp mask fix.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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