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

From: Markus Armbruster
Subject: Re: [Qemu-devel] [PATCH v2 02/42] exec: Fix memory allocation when memory path isn't on hugetlbfs
Date: Tue, 15 Mar 2016 17:41:56 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)

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?

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