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From: Chen Gang <chengang@emindsoft.com.cn>
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Date: Thu, 14 Jan 2016 18:26:19 +0800
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Subject: Re: [Qemu-devel] [PATCH] translate-all.c: Remove writable
 protection feature for tb_alloc_page()
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>, QEMU Developers <qemu-devel@nongnu.org>, Peter Crosthwaite <crosthwaite.peter@gmail.com>

On 2016年01月14日 18:05, Peter Maydell wrote:
> On 14 January 2016 at 06:03,  <chengang@emindsoft.com.cn> wrote:
>> From: Chen Gang <chengang@emindsoft.com.cn>
>>
>> Guest may allocate a readable, writable, and executable page, then write
>> data on the page, and execute data as code on the page too, then write
>> anther data still within the page.
>>
>> So remove this feature from linux-user: it not only consumes a little
>> performance, but also causes issue with the old Linux kernel under some
>> of architectures (they will directly generate segment fault for it).
> 
> If we don't mark the page as non-writeable when we generate a TB
> from it, how do we detect when guest code later writes to that
> page (which means we need to invalidate the TB) ?
> 

For me, what you said above sounds reasonable, at present, that's really
valuable to me :-)

I guess, you also mean: our qemu will catch the host page fault signal
and invalidate the TB.

Thanks.
-- 
Chen Gang (陈刚)

Open, share, and attitude like air, water, and life which God blessed