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Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags f
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag() |
Date: |
Tue, 26 Jan 2016 09:11:48 +0000 |
On 26 January 2016 at 02:58, Chen Gang <address@hidden> wrote:
> The related comments for "if (prot1 == 0)" code block is "no page was
> there, so we allocate one".
>
> So I guess this code block is not only allocate page for guest, but also
> for host. So prot1 is not only for the guest page, but also for host
> page.
The comment means specifically "allocate a host page".
> If we do not page_set_flags with PAGE_VALID, The next call
> in mmap_frag for the same area will let prot1 be 0, so still
> fall into "if (prot1 == 0)" code block.
But in what case will we call mmap_frag() again before we
call page_set_flags() at the bottom of target_mmap()?
That is what is not clear to me, and why I asked you to describe
what the case is that you're seeing problems with.
Reading the target_mmap() code, its intention seems to be:
(a) if the whole allocation fits in one host page, call
mmap_frag() once and then "goto the_end1"
(b) otherwise, we'll call mmap_frag() once for the start
of the guest mapping, and once for the end, which must
be two different host pages
So if you're seeing mmap_frag() called twice for the same
host page then something is going wrong, but I'm not sure what.
thanks
-- PMM
- [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(), chengang, 2016/01/11
- [Qemu-devel] [PATCH v2 2/3] linux-user/mmap.c: Remove useless variable p for mmap_frag, chengang, 2016/01/11
- [Qemu-devel] [PATCH v2 3/3] linux-user/mmap.c: Use TARGET_PAGE_SIZE as the increasing step, chengang, 2016/01/11
- Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(), Peter Maydell, 2016/01/25
- Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(), Chen Gang, 2016/01/25
- Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(),
Peter Maydell <=
- Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(), Chen Gang, 2016/01/26
- Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(), Peter Maydell, 2016/01/26
- Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(), Chen Gang, 2016/01/26
- Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(), Peter Maydell, 2016/01/28
- Re: [Qemu-devel] [PATCH v2 1/3] linux-user/mmap.c: Set prot page flags for the correct region in mmap_frag(), Chen Gang, 2016/01/28