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Subject: Re: [PATCH v2 1/1] s390/pv: fix the forcing of the swiotlb
To:     Konrad Rzeszutek Wilk <konrad@darnok.org>,
        Halil Pasic <pasic@linux.ibm.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        Nathan Chancellor <nathan@kernel.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        linux-s390 <linux-s390@vger.kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Heiko Carstens <hca@linux.ibm.com>, stable@vger.kernel.org,
        Claire Chang <tientzu@chromium.org>,
        Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
        Guenter Roeck <linux@roeck-us.net>
References: <20210723231746.3964989-1-pasic@linux.ibm.com>
 <YPtejB62iu+iNrM+@fedora>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
Message-ID: <a89f1add-b0fb-1069-cb30-78864e399b19@de.ibm.com>
Date:   Tue, 27 Jul 2021 14:54:14 +0200
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On 24.07.21 02:27, Konrad Rzeszutek Wilk wrote:
> On Sat, Jul 24, 2021 at 01:17:46AM +0200, Halil Pasic wrote:
>> 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 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 <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: 64e1f0c531d1 ("s390/mm: force swiotlb for protected virtualization")
>> Cc: stable@vger.kernel.org #5.3+
>>
>> ---
> 
> Picked it up and stuck it in linux-next with the other set of patches (Will's fixes).

Can you push out to kernel.org?