Re: [Xen-devel] [PATCH] xen-mapcache: use MAP_FIXED flag so the mmap address hint is always honored

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Fri, Mar 15, 2019 at 09:54:42AM +0000, Paul Durrant wrote:
> AFAICT xen_remap_bucket() is always called with a NULL vaddr argument
> if entry->vaddr_base == NULL, and called with vaddr ==
> entry->vaddr_base in the other case, so I'd say the vaddr argument is
> superfluous.

I don't think that's true. The call at line 312 [1] may be called with
vaddr_base != NULL. Then, xen_remap_bucket will unmap that entry before
replacing it.

We could maybe figure out if vaddr_base needs to be replaced in-place
based on the flags XEN_MAPCACHE_ENTRY_DUMMY, but that seems more
convoluted than the current approche.

[1] 
https://git.qemu.org/?p=qemu.git;a=blob;f=hw/i386/xen/xen-mapcache.c;h=349f72d00cc2c9fc134df8cff7dd051b1fc2fa41;hb=HEAD#l312

-- 
Anthony PERARD

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