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Re: [Qemu-devel] [PATCH v2 02/42] exec: Fix memory allocation when memor

From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH v2 02/42] exec: Fix memory allocation when memory path isn't on hugetlbfs
Date: Tue, 15 Mar 2016 17:56:52 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

On 15/03/2016 17:41, Markus Armbruster wrote:
> Paolo Bonzini <address@hidden> writes:
>> On 07/03/2016 20:25, Markus Armbruster wrote:
>>> gethugepagesize() works reliably only when its argument is on
>>> hugetlbfs.  When it's not, it returns the filesystem's "optimal
>>> transfer block size", which may or may not be the actual page size
>>> you'll get when you mmap().
>>> If the value is too small or not a power of two, we fail
>>> qemu_ram_mmap()'s assertions.  These were added in commit 794e8f3
>>> (v2.5.0).  The bug's impact before that is currently unknown.  Seems
>>> fairly unlikely at least when the normal page size is 4KiB.
>>> Else, if the value is too large, we align more strictly than
>>> necessary.
>>> gethugepagesize() goes back to commit c902760 (v0.13).  That commit
>>> clearly intended gethugepagesize() to be used on hugetlbfs only.  Not
>>> only was it named accordingly, it also printed a warning when used on
>>> anything else.  However, the commit neglected to spell out the
>>> restriction in user documentation of -mem-path.
>>> Commit bfc2a1a (v2.5.0) dropped the warning as bogus "because QEMU
>>> functions perfectly well with the path on a regular tmpfs filesystem".
>>> It sure does when you're sufficiently lucky.  In my testing, I was
>>> lucky, too.
>>> Fix by switching to qemu_fd_getpagesize().  Rename the variable
>>> holding its result from hpagesize to page_size.
>>> Cc: Paolo Bonzini <address@hidden>
>>> Signed-off-by: Markus Armbruster <address@hidden>
> [...]
>> Queued, thanks.
> Not in master, yet.  What repo+branch should I use as base for v3?

I'll send a pull request later today, keep an eye on it.


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