Subject: Re: powerpc/64s/radix: Fix missing ptesync in flush_cache_vmap

From: Michael Ellerman <[email-masked]>
Date: Thu, 7 Jun 2018 10:17:43 +1000 (AEST)

On Wed, 2018-06-06 at 01:40:08 UTC, Nicholas Piggin wrote:
> There is a typo in f1cb8f9beb ("powerpc/64s/radix: avoid ptesync after
> set_pte and ptep_set_access_flags") config ifdef, which results in the
> necessary ptesync not being issued after vmalloc.
> 
> This causes random kernel faults in module load, bpf load, anywhere
> that vmalloc mappings are used.
> 
> After correcting the code, this survives a guest kernel booting
> hundreds of times where previously there would be a crash every few
> boots (I haven't noticed the crash on host, perhaps due to different
> TLB and page table walking behaviour in hardware).
> 
> A memory clobber is also added to the flush, just to be sure it won't
> be reordered with the pte set or the subsequent mapping access.
> 
> Fixes: f1cb8f9beb ("powerpc/64s/radix: avoid ptesync after set_pte and ptep_set_access_flags")
> Signed-off-by: Nicholas Piggin <[email-masked]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/ff5bc793e47b537bf3e904fada585e

cheers