linux-kernel - Re: [PATCH] KVM: x86: emulate: correct page fault error code for NoWrite instructions

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Message-Id: <346BBAFD-80C9-4C26-89B7-0F9ECD5D1DA0@gmail.com>
Date:	Fri, 20 Nov 2015 09:46:07 +0200
From:	Nadav Amit <nadav.amit@...il.com>
To:	Wanpeng Li <kernellwp@...il.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH] KVM: x86: emulate: correct page fault error code for NoWrite instructions

Wanpeng Li <kernellwp@...il.com> wrote:

> 2015-11-20 10:52 GMT+08:00 Wanpeng Li <kernellwp@...il.com>:
>> Hi Paolo,
>> 2015-02-09 17:03 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
>>> NoWrite instructions (e.g. cmp or test) never set the "write access"
>>> bit in the error code, even if one of the operands is treated as a
>>> destination.
>> 
>> Sorry to reply to an old commit, btw, could you point out where in SDM
>> describe above?
> 
> I see.

I don’t understand whether you still need my help, so to clarify: on a
page-fault the error code should indicate whether the access was due to a
write access. Previously KVM marked it as “write access” for instructions
such as test and cmp that do not perform write.

Nadav--
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