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Re: [Qemu-devel] [PATCH] sparc: Make sure we mmap at SHMLBA alignment


From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH] sparc: Make sure we mmap at SHMLBA alignment
Date: Mon, 11 Dec 2017 21:53:13 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0

On 12/08/2017 08:57 AM, Peter Maydell wrote:
> SPARC Linux has an oddity that it insists that mmap()
> of MAP_FIXED memory must be at an alignment defined by
> SHMLBA, which is more aligned than the page size
> (typically, SHMLBA alignment is to 16K, and pages are 8K).
> This is a relic of ancient hardware that had cache
> aliasing constraints, but even on modern hardware the
> kernel still insists on the alignment.
> 
> To ensure that we get mmap() alignment sufficient to
> make the kernel happy, change QEMU_VMALLOC_ALIGN,
> qemu_fd_getpagesize() and qemu_mempath_getpagesize()
> to use the maximum of getpagesize() and SHMLBA.
> 
> In particular, this allows 'make check' to pass on Sparc:
> we were previously failing the ivshmem tests.
> 
> Signed-off-by: Peter Maydell <address@hidden>
> ---

Reviewed-by: Richard Henderson <address@hidden>

r~



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