linux-kernel - Re: [PATCH v2 1/1] iommu/arm-smmu-v3: Fix error case of range command

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Message-ID: <dafbccb4-f7be-838f-c037-91ff2dc324e4@linux.microsoft.com>
Date:   Tue, 5 Sep 2023 22:05:04 -0700
From:   Easwar Hariharan <eahariha@...ux.microsoft.com>
To:     zhurui <zhurui3@...wei.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>
Cc:     Nicolin Chen <nicolinc@...dia.com>,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Yicong Yang <yangyicong@...ilicon.com>,
        Tomas Krcka <krckatom@...zon.de>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [PATCH v2 1/1] iommu/arm-smmu-v3: Fix error case of range command

On 8/25/23 01:12, zhurui wrote:
> On 2023/8/19 0:21, Will Deacon wrote:
>> On Fri, Aug 18, 2023 at 05:19:31PM +0100, Robin Murphy wrote:
>>> On 2023-08-09 14:48, Robin Murphy wrote:
>>> [...]
>>>> Does the patch below work for you?
>>>
>>> Any comments on this? Just noticed this commit on a local dev branch and
>>> realised I'd totally forgotten about it already. I'm pretty confident it
>>> ought to be right, but then it *was* also me who missed the original bug to
>>> begin with... ;)
>>
>> I'm happy to take it if zhurui can confirm that it fixes their issue...
>>
>> Will (had also forgotten about this)
>>
>>>> ----->8-----
>>>> Subject: [PATCH] iommu/arm-smmu-v3: Avoid constructing invalid range
>>>> commands
>>>>
>>>> Although io-pgtable's non-leaf invalidations are always for full tables,
>>>> I missed that SVA also uses non-leaf invalidations, while being at the
>>>> mercy of whatever range the MMU notifier throws at it. This means it
>>>> definitely wants the previous TTL fix as well, since it also doesn't
>>>> know exactly which leaf level(s) may need invalidating, but it can also
>>>> give us less-aligned ranges wherein certain corners may lead to building
>>>> an invalid command where TTL, Num and Scale are all 0. It should be fine
>>>> to handle this by over-invalidating an extra page, since falling back to
>>>> a non-range command opens up a whole can of errata-flavoured worms.
>>>>
>>>> Fixes: 6833b8f2e199 ("iommu/arm-smmu-v3: Set TTL invalidation hint better")
>>>> Reported-by: Rui Zhu <zhurui3@...wei.com>
>>>> Signed-off-by: Robin Murphy <robin.murphy@....com>
>>>> ---
>>>>    drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 15 ++++++++++-----
>>>>    1 file changed, 10 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>>> b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>>> index 9b0dc3505601..6ccbae9b93a1 100644
>>>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>>> @@ -1895,18 +1895,23 @@ static void __arm_smmu_tlb_inv_range(struct
>>>> arm_smmu_cmdq_ent *cmd,
>>>>            /* Get the leaf page size */
>>>>            tg = __ffs(smmu_domain->domain.pgsize_bitmap);
>>>>
>>>> +        num_pages = size >> tg;
>>>> +
>>>>            /* Convert page size of 12,14,16 (log2) to 1,2,3 */
>>>>            cmd->tlbi.tg = (tg - 10) / 2;
>>>>
>>>>            /*
>>>> -         * Determine what level the granule is at. For non-leaf,
>>>> io-pgtable
>>>> -         * assumes .tlb_flush_walk can invalidate multiple levels at once,
>>>> -         * so ignore the nominal last-level granule and leave TTL=0.
>>>> +         * Determine what level the granule is at. For non-leaf, both
>>>> +         * io-pgtable and SVA pass a nominal last-level granule because
>>>> +         * they don't know what level(s) actually apply, so ignore that
>>>> +         * and leave TTL=0. However for various errata reasons we still
>>>> +         * want to use a range command, so avoid the SVA corner case
>>>> +         * where both scale and num could be 0 as well.
>>>>             */
>>>>            if (cmd->tlbi.leaf)
>>>>                cmd->tlbi.ttl = 4 - ((ilog2(granule) - 3) / (tg - 3));
>>>> -
>>>> -        num_pages = size >> tg;
>>>> +        else if ((num_pages & CMDQ_TLBI_RANGE_NUM_MAX) == 1)
>>>> +            num_pages++;
>>>>        }
>>>>
>>>>        cmds.num = 0;
>>>>
> 
> Hi, Will and Robin,
> Sorry for taking so long to reply you. We have some problems with our machine these days. It's
> solved just today. I give a test with Robin's patch for our testcase, everything is ok. I think
> the problem has been solved.
> 
> Thanks,
> ZhuRui.
>

Hi Robin,

Could you please send out this patch since ZhuRui has confirmed it fixes 
their issue and CC it to stable for v5.15+? Or if Will is willing to 
pick it up off this thread, I can do the backport to stable.

-- 
Thanks,
Easwar