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    SubjectRe: [PATCH v2 1/1] iommu/arm-smmu-v3: Fix error case of range command
    On Sun, Aug 06, 2023 at 01:28:04PM +0800, zhurui wrote:
    > On 2023/8/5 2:30, Nicolin Chen wrote:
    > > On Fri, Aug 04, 2023 at 05:52:25PM +0100, Will Deacon wrote:
    > >> On Fri, Aug 04, 2023 at 05:31:20PM +0800, zhurui wrote:
    > >>> When tg != 0 but ttl, scale, num all 0 in a range tlbi command, it
    > >>> is reserved and will cause the CERROR_ILL error. This case means
    > >>> that the size to be invalidated is only one page size, and the
    > >>> range invalidation is meaningless here. So we set tg to 0 in this
    > >>> case to do an non-range invalidation instead.
    > >
    > >>> @@ -1930,6 +1927,12 @@ static void __arm_smmu_tlb_inv_range(struct arm_smmu_cmdq_ent *cmd,
    > >>> num = (num_pages >> scale) & CMDQ_TLBI_RANGE_NUM_MAX;
    > >>> cmd->tlbi.num = num - 1;
    > >>>
    > >>> + /* Prevent error caused by one page tlbi with leaf 0 */
    > >>> + if (scale == 0 && num == 1 && cmd->tlbi.leaf == 0)
    > >>> + cmd->tlbi.tg = 0;
    > >>
    > >> This should only be true for the last iteration, right (i.e. when num_pages
    > >> == 1)? In which case, I'd prefer to leave the old code as-is and just add:
    > >>
    > >> /* Single-page leaf invalidation requires a TG field of 0 */
    > >> if (num_pages == 1 && !cmd->tlbi.leaf)
    > >> cmd->tlbi.tg = 0;To Will and Nicolin,
    >
    > Not only the last iteration, it's the result of __ffs function. For example, if
    > numpages is 33, then the value of __ffs(num_pages) is 0, so the value of scale
    > is also 0. The value of num depends on CMDQ_TLBI_RANGE_NUM_MAX. That is, the
    > maximum value of num is 31. Therefore, the final value of num is 1.
    > So, if consider CMDQ_TLBI_RANGE_NUM_MAX, there will be some case not the last
    > one page but the beginning pages. That's why I use scale and num as conditions,
    > not num_pages. Then I should reassign tg based on the result.

    Yes, thanks, you're quite right. I'm not sure what I was thinking!

    Will

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