Messages in this thread | | | Subject | Re: [PATCH 06/24] x86,kvm: Fix indirect calls in emulator | From | Paolo Bonzini <> | Date | Fri, 26 Jan 2018 11:57:00 +0100 |
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On 25/01/2018 10:34, Peter Zijlstra wrote: > On Wed, Jan 24, 2018 at 11:43:05AM +0100, Paolo Bonzini wrote: >> On 24/01/2018 11:35, Peter Zijlstra wrote: >>> On Tue, Jan 23, 2018 at 08:48:13PM +0000, David Woodhouse wrote: >>>> On Tue, 2018-01-23 at 21:28 +0100, Borislav Petkov wrote: >>>>> >>>>>> flags = (flags & EFLAGS_MASK) | X86_EFLAGS_IF; >>>>>> - asm("push %[flags]; popf; call *%[fastop]" >>>>>> - : "=a"(rc) : [fastop]"r"(fop), [flags]"r"(flags)); >>>>>> + asm("push %[flags]; popf; " CALL_NOSPEC >>>>>> + : "=a"(rc) : [thunk_target]"r"(fop), [flags]"r"(flags)); >>>>> >>>>> Oh, "thunk_target" is magical. >>>> >>>> You can use THUNK_TARGET(fop), which will be "rm" on 32-bit and avoids >>>> register starvation in some cases (I don't think the hyperv calls >>>> worked until I did that). >>> >>> The reason I didn't use THUNK_TARGET() was exactly because it used "rm" >>> and the current code did "r" only. I'm happy to change if people can >>> agree on something ;-) >> >> In practice, "fastop" is going to be in a register because of how it's >> computed, but "rm" is okay. > > OK, so the other occurence in that file uses "+S", which is the SI > register. That cannot use THUNK_TARGET(), right?
Nope, it reads the output in %esi too.
> So do you want one THUNK_TARGET and one open coded, or keep the patch as > is (both open coded) ?
Open coded is okay.
Paolo
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