s390/kvm: simplify set_guest_storage_key
Git commit ab3f285f "KVM: s390/mm: try a cow on read only pages for key ops" added a fixup_user_fault to set_guest_storage_key force a copy on write if the page is mapped read-only. This is supposed to fix the problem of differing storage keys for shared mappings, e.g. the empty_zero_page. But if the storage key is set before the pte is mapped the storage key update is done on the pgste. A later fault will happily map the shared page with the key from the pgste. Eventually git commit 2faee8ff "s390/mm: prevent and break zero page mappings in case of storage keys" fixed this problem for the empty_zero_page. The commit makes sure that guests enabled for storage keys will not use the empty_zero_page at all. As the call to fixup_user_fault in set_guest_storage_key depends on the order of the storage key operation vs. the fault that maps the pte it does not really fix anything. Just remove it. Reviewed-by: NDominik Dingel <dingel@linux.vnet.ibm.com> Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>
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