linux-kernel - Re: [PATCH v2 1/1] s390/pv: fix the forcing of the swiotlb

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Message-ID: <827b1bd3-3245-fe0e-0066-cadf8cab432f@de.ibm.com>
Date:   Tue, 27 Jul 2021 15:00:05 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Will Deacon <will@...nel.org>
Cc:     Konrad Rzeszutek Wilk <konrad@...nok.org>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Robin Murphy <robin.murphy@....com>,
        Heiko Carstens <hca@...ux.ibm.com>, stable@...r.kernel.org,
        Claire Chang <tientzu@...omium.org>,
        Christoph Hellwig <hch@....de>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH v2 1/1] s390/pv: fix the forcing of the swiotlb



On 27.07.21 14:57, Will Deacon wrote:
> On Tue, Jul 27, 2021 at 02:54:14PM +0200, Christian Borntraeger wrote:
>>
>> 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@...ux.ibm.com>
>>>> Tested-by: Christian Borntraeger <borntraeger@...ibm.com>
>>>> Reviewed-by: Christian Borntraeger <borntraeger@...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@...r.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?
> 
> It's pushed to the swiotlb tree:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb.git/log/?h=devel/for-linus-5.15
> 
> Since none of the restricted DMA series is in mainline yet, I don't think
> it's needed anywhere else.

Ah right. It is not yet in todays next, so it might just be that yesterdays next pulled
from Konrad too early. Sorry for the noise.