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

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Date:   Fri, 25 Aug 2023 16:12:00 +0800
From:   zhurui <zhurui3@...wei.com>
To:     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 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.