archive mirror
 help / color / mirror / Atom feed
From: Halil Pasic <>
To: Konrad Rzeszutek Wilk <>,,,
	Christian Borntraeger <>
Cc: Halil Pasic <>,, Guenter Roeck <>,
	Will Deacon <>,
	Claire Chang <>,
	Christoph Hellwig <>,
	Robin Murphy <>,
	Nathan Chancellor <>,
	linux-s390 <>,
	Vasily Gorbik <>,
	Heiko Carstens <>
Subject: [PATCH v2 1/1] s390/pv: fix the forcing of the swiotlb
Date: Sat, 24 Jul 2021 01:17:46 +0200	[thread overview]
Message-ID: <> (raw)

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

This change addresses what turned out to be a fragility in
commit 64e1f0c531d1 ("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 <>
Tested-by: Christian Borntraeger <>
Reviewed-by: Christian Borntraeger <>
Fixes: 903cd0f315fe ("swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing")
Fixes: 64e1f0c531d1 ("s390/mm: force swiotlb for protected virtualization")
Cc: #5.3+


I'm aware that this fix does not really satisfy the formal requirements
for the stable process. But to avoid problems with backports we would
like this fix applied to 5.3+ stable kernels.
 arch/s390/mm/init.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index d85bd7f5d8dc..1c8f8ccebfb7 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -186,9 +186,9 @@ static void pv_init(void)
 	/* make sure bounce buffers are shared */
+	swiotlb_force = SWIOTLB_FORCE;
-	swiotlb_force = SWIOTLB_FORCE;
 void __init mem_init(void)

base-commit: 90d856e71443a2fcacca8e7539bac44d9cb3f7ab

             reply	other threads:[~2021-07-23 23:18 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-23 23:17 Halil Pasic [this message]
2021-07-24  0:27 ` Konrad Rzeszutek Wilk
2021-07-26 15:25   ` Halil Pasic
2021-07-27 12:54   ` Christian Borntraeger
2021-07-27 12:57     ` Will Deacon
2021-07-27 13:00       ` Christian Borntraeger

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [PATCH v2 1/1] s390/pv: fix the forcing of the swiotlb' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox