s390/pv: fix the forcing of the swiotlb
authorHalil Pasic <pasic@linux.ibm.com>
Fri, 23 Jul 2021 23:17:46 +0000 (01:17 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 22 Sep 2021 10:26:37 +0000 (12:26 +0200)
commit 93ebb6828723b8aef114415c4dc3518342f7dcad upstream.

Since commit 903cd0f315fe ("swiotlb: Use is_swiotlb_force_bounce for
swiotlb data bouncing") if code sets swiotlb_force it needs to do so
before the swiotlb is initialised. Otherwise
io_tlb_default_mem->force_bounce will not get set to true, and devices
that use (the default) swiotlb will not bounce despite switolb_force
having the value of SWIOTLB_FORCE.

Let us restore swiotlb functionality for PV by fulfilling this new
requirement.

This change addresses what turned out to be a fragility in
commit f346608fa678 ("s390/mm: force swiotlb for protected
virtualization"), which ain't exactly broken in its original context,
but could give us some more headache if people backport the broken
change and forget this fix.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Fixes: 903cd0f315fe ("swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing")
Fixes: f346608fa678 ("s390/mm: force swiotlb for protected virtualization")
Cc: stable@vger.kernel.org #5.3+
Signed-off-by: Konrad Rzeszutek Wilk <konrad@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/s390/mm/init.c

index c1d96e588152bb799530b3569bdfd26a0d7af097..5521f593cd20a41162a5e7ddf2ae332c0cae772b 100644 (file)
@@ -168,9 +168,9 @@ static void pv_init(void)
                return;
 
        /* make sure bounce buffers are shared */
+       swiotlb_force = SWIOTLB_FORCE;
        swiotlb_init(1);
        swiotlb_update_mem_attributes();
-       swiotlb_force = SWIOTLB_FORCE;
 }
 
 void __init mem_init(void)