[PATCH 4.16.y] swiotlb: fix unexpected swiotlb_alloc_coherent failures

[PATCH 4.16.y] swiotlb: fix unexpected swiotlb_alloc_coherent failures

[Takashi Iwai]

commit 9e7f06c8beee304ee21b791653fefcd713f48b9a upstream.

The code refactoring by commit 0176adb00406 ("swiotlb: refactor coherent
buffer allocation") made swiotlb_alloc_buffer almost always failing due
to a thinko: namely, the function evaluates the dma_coherent_ok call
incorrectly and dealing as if it's invalid. This ends up with weird
errors like iwlwifi probe failure or amdgpu screen flickering.

This patch corrects the logic error.

Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088658
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088902
Fixes: 0176adb00406 ("swiotlb: refactor coherent buffer allocation")
Cc: <stable@vger.kernel.org> # v4.16+
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---

Greg, this is a commit that felt out in the previous round due to
cherry-pick error.  Resent with a context fix.

 lib/swiotlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index c43ec2271469..44f7eb408fdb 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -732,7 +732,7 @@ swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		goto out_warn;
 
 	*dma_handle = swiotlb_phys_to_dma(dev, phys_addr);
-	if (dma_coherent_ok(dev, *dma_handle, size))
+	if (!dma_coherent_ok(dev, *dma_handle, size))
 		goto out_unmap;
 
 	memset(phys_to_virt(phys_addr), 0, size);
-- 
2.16.3

Re: [PATCH 4.16.y] swiotlb: fix unexpected swiotlb_alloc_coherent failures

[Greg Kroah-Hartman]

On Thu, Apr 19, 2018 at 08:19:09AM +0200, Takashi Iwai wrote:
> commit 9e7f06c8beee304ee21b791653fefcd713f48b9a upstream.
> 
> The code refactoring by commit 0176adb00406 ("swiotlb: refactor coherent
> buffer allocation") made swiotlb_alloc_buffer almost always failing due
> to a thinko: namely, the function evaluates the dma_coherent_ok call
> incorrectly and dealing as if it's invalid. This ends up with weird
> errors like iwlwifi probe failure or amdgpu screen flickering.
> 
> This patch corrects the logic error.
> 
> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088658
> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088902
> Fixes: 0176adb00406 ("swiotlb: refactor coherent buffer allocation")
> Cc: <stable@vger.kernel.org> # v4.16+
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> 
> Greg, this is a commit that felt out in the previous round due to
> cherry-pick error.  Resent with a context fix.

Now queued up, thanks.

greg k-h