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Re: [Qemu-devel] [PATCH] translate-all.c: Remove writable protection fea
From: |
Chen Gang |
Subject: |
Re: [Qemu-devel] [PATCH] translate-all.c: Remove writable protection feature for tb_alloc_page() |
Date: |
Thu, 14 Jan 2016 18:26:19 +0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 |
On 2016年01月14日 18:05, Peter Maydell wrote:
> On 14 January 2016 at 06:03, <address@hidden> wrote:
>> From: Chen Gang <address@hidden>
>>
>> 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