Re: [PATCH] xen: replace xen_remap() with memremap()

[Boris Ostrovsky <boris.ostrovsky@oracle.com>]

On 5/30/22 4:26 AM, Juergen Gross wrote:
> xen_remap() is used to establish mappings for frames not under direct
> control of the kernel: for Xenstore and console ring pages, and for
> grant pages of non-PV guests.
>
> Today xen_remap() is defined to use ioremap() on x86 (doing uncached
> mappings), and ioremap_cache() on Arm (doing cached mappings).
>
> Uncached mappings for those use cases are bad for performance, so they
> should be avoided if possible. As all use cases of xen_remap() don't
> require uncached mappings (the mapped area is always physical RAM),
> a mapping using the standard WB cache mode is fine.
>
> As sparse is flagging some of the xen_remap() use cases to be not
> appropriate for iomem(), as the result is not annotated with the
> __iomem modifier, eliminate xen_remap() completely and replace all
> use cases with memremap() specifying the MEMREMAP_WB caching mode.
>
> xen_unmap() can be replaced with memunmap().
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Juergen Gross <jgross@suse.com>



Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>