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From: David Edmondson <dme@dme.org>
To: Jim Mattson <jmattson@google.com>
Cc: Sean Christopherson <seanjc@google.com>,
	Aaron Lewis <aaronlewis@google.com>,
	kvm list <kvm@vger.kernel.org>
Subject: Re: [PATCH 1/2] kvm: x86: Allow userspace to handle emulation errors
Date: Wed, 21 Apr 2021 18:01:35 +0100	[thread overview]
Message-ID: <cunpmynfu6o.fsf@dme.org> (raw)
In-Reply-To: <CALMp9eQZLe_8esohDqt_0eLffOrAeC0vS1RSVw152z2RhmPntw@mail.gmail.com>

On Wednesday, 2021-04-21 at 09:26:34 -07, Jim Mattson wrote:

> On Wed, Apr 21, 2021 at 1:39 AM David Edmondson <dme@dme.org> wrote:
>>
>> On Tuesday, 2021-04-20 at 18:34:48 UTC, Sean Christopherson wrote:
>>
>> > On Fri, Apr 16, 2021, Aaron Lewis wrote:
>> >> +                    KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES;
>> >> +            vcpu->run->emulation_failure.insn_size = insn_size;
>> >> +            memcpy(vcpu->run->emulation_failure.insn_bytes,
>> >> +                   ctxt->fetch.data, sizeof(ctxt->fetch.data));
>> >
>> > Doesn't truly matter, but I think it's less confusing to copy over insn_size
>> > bytes.
>
>> And zero out the rest?
>
> Why zero? Since we're talking about an instruction stream, wouldn't
> 0x90 make more sense than zero?

I'm not sure if you are serious or not.

Zero-ing out the rest was intended to be to avoid leaking any previous
emulated instruction stream. If the user-level code wants to start
looking for instructions after insn_bytes[insn_size], they get what they
deserve.

dme.
-- 
We're deep in discussion, the party's on mute.

  reply	other threads:[~2021-04-21 17:01 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 13:18 [PATCH 1/2] kvm: x86: Allow userspace to handle emulation errors Aaron Lewis
2021-04-16 13:18 ` [PATCH 2/2] selftests: kvm: Allows " Aaron Lewis
2021-04-19 12:41 ` [PATCH 1/2] kvm: x86: Allow " David Edmondson
2021-04-19 16:47   ` Aaron Lewis
2021-04-20  7:21     ` David Edmondson
2021-04-20 14:57       ` Aaron Lewis
2021-04-20 16:53         ` David Edmondson
2021-04-20 18:21           ` Sean Christopherson
2021-04-21  8:00             ` David Edmondson
2021-04-20 18:34 ` Sean Christopherson
2021-04-21  8:39   ` David Edmondson
2021-04-21 12:47     ` Aaron Lewis
2021-04-21 16:26     ` Jim Mattson
2021-04-21 17:01       ` David Edmondson [this message]
2021-04-21 17:28         ` Jim Mattson
2021-04-21 16:31   ` Jim Mattson

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