Re: [PATCH v2] s390/mm: add missing secure storage access fixups for donated memory

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 10.03.26 um 16:02 schrieb Janosch Frank:
> There are special cases where secure storage access exceptions happen
> in a kernel context for pages that don't have the PG_arch_1 bit
> set. That bit is set for non-exported guest secure storage (memory)
> but is absent on storage donated to the Ultravisor since the kernel
> isn't allowed to export donated pages.
> 
> Prior to this patch we would try to export the page by calling
> arch_make_folio_accessible() which would instantly return since the
> arch bit is absent signifying that the page was already exported and
> no further action is necessary. This leads to secure storage access
> exception loops which can never be resolved.
> 
> With this patch we unconditionally try to export and if that fails we
> fixup.
> 
> Fixes: 084ea4d611a3 ("s390/mm: add (non)secure page access exceptions handlers")
> Reported-by: Heiko Carstens <hca@linux.ibm.com>
> Suggested-by: Heiko Carstens <hca@linux.ibm.com>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

Tested-by: Christian Borntraeger <borntraeger@linux.ibm.com>