Messages in this thread | | | Subject | Re: [PATCH v3 4/6] iommu/io-pgtable-arm: add support for non-strict mode | From | "Leizhen (ThunderTown)" <> | Date | Tue, 14 Aug 2018 16:33:41 +0800 |
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On 2018/8/6 9:32, Yang, Shunyong wrote: > Hi, Robin, > > On 2018/7/26 22:37, Robin Murphy wrote: >> On 2018-07-26 8:20 AM, Leizhen (ThunderTown) wrote: >>> On 2018/7/25 6:25, Robin Murphy wrote: >>>> On 2018-07-12 7:18 AM, Zhen Lei wrote: >>>>> To support the non-strict mode, now we only tlbi and sync for the strict >>>>> mode. But for the non-leaf case, always follow strict mode. >>>>> >>>>> Use the lowest bit of the iova parameter to pass the strict mode: >>>>> 0, IOMMU_STRICT; >>>>> 1, IOMMU_NON_STRICT; >>>>> Treat 0 as IOMMU_STRICT, so that the unmap operation can compatible with >>>>> other IOMMUs which still use strict mode. >>>>> >>>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >>>>> --- >>>>> drivers/iommu/io-pgtable-arm.c | 23 ++++++++++++++--------- >>>>> 1 file changed, 14 insertions(+), 9 deletions(-) >>>>> >>>>> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c >>>>> index 010a254..9234db3 100644 >>>>> --- a/drivers/iommu/io-pgtable-arm.c >>>>> +++ b/drivers/iommu/io-pgtable-arm.c >>>>> @@ -292,7 +292,7 @@ static void __arm_lpae_set_pte(arm_lpae_iopte *ptep, arm_lpae_iopte pte, >>>>> static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, >>>>> unsigned long iova, size_t size, int lvl, >>>>> - arm_lpae_iopte *ptep); >>>>> + arm_lpae_iopte *ptep, int strict); >>>>> static void __arm_lpae_init_pte(struct arm_lpae_io_pgtable *data, >>>>> phys_addr_t paddr, arm_lpae_iopte prot, >>>>> @@ -334,7 +334,7 @@ static int arm_lpae_init_pte(struct arm_lpae_io_pgtable *data, >>>>> size_t sz = ARM_LPAE_BLOCK_SIZE(lvl, data); >>>>> tblp = ptep - ARM_LPAE_LVL_IDX(iova, lvl, data); >>>>> - if (WARN_ON(__arm_lpae_unmap(data, iova, sz, lvl, tblp) != sz)) >>>>> + if (WARN_ON(__arm_lpae_unmap(data, iova, sz, lvl, tblp, IOMMU_STRICT) != sz)) >>>>> return -EINVAL; >>>>> } >>>>> @@ -531,7 +531,7 @@ static void arm_lpae_free_pgtable(struct io_pgtable *iop) >>>>> static size_t arm_lpae_split_blk_unmap(struct arm_lpae_io_pgtable *data, >>>>> unsigned long iova, size_t size, >>>>> arm_lpae_iopte blk_pte, int lvl, >>>>> - arm_lpae_iopte *ptep) >>>>> + arm_lpae_iopte *ptep, int strict) >>>> >>>> DMA code should never ever be splitting blocks anyway, and frankly the TLB maintenance here is dodgy enough (since we can't reasonably do break-before make as VMSA says we should) that I *really* don't want to introduce any possibility of making it more asynchronous. I'd much rather just hard-code the expectation of strict == true for this. >>> >>> OK, I will hard-code strict=true for it. >>> >>> But since it never ever be happened, why did not give a warning at the beginning? >> >> Because DMA code is not the only caller of iommu_map/unmap. It's >> perfectly legal in the IOMMU API to partially unmap a previous mapping >> such that a block entry needs to be split. The DMA API, however, is a >> lot more constrined, and thus by construction the iommu-dma layer will >> never generate a block-splitting iommu_unmap() except as a result of >> illegal DMA API usage, and we obviously do not need to optimise for that >> (you will get a warning about mismatched unmaps under dma-debug, but >> it's a bit too expensive to police in the general case). >> > > When I was reading the code around arm_lpae_split_blk_unmap(), I was > curious in which scenario a block will be split. Now with your comments > "Because DMA code is not the only caller of iommu_map/unmap", it seems > depending on the user. > > Would you please explain this further? I mean besides DMA, which user > will use iommu_map/umap and how it split a block.
I also think that arm_lpae_split_blk_unmap() scenario is not exist, maybe we should remove it, and give a warning for this wrong usage.
> > Thanks. > Shunyong. > >> >>>>> { >>>>> struct io_pgtable_cfg *cfg = &data->iop.cfg; >>>>> arm_lpae_iopte pte, *tablep; >>>>> @@ -576,15 +576,18 @@ static size_t arm_lpae_split_blk_unmap(struct arm_lpae_io_pgtable *data, >>>>> } >>>>> if (unmap_idx < 0) >>>>> - return __arm_lpae_unmap(data, iova, size, lvl, tablep); >>>>> + return __arm_lpae_unmap(data, iova, size, lvl, tablep, strict); >>>>> io_pgtable_tlb_add_flush(&data->iop, iova, size, size, true); >>>>> + if (!strict) >>>>> + io_pgtable_tlb_sync(&data->iop); >>>>> + >>>>> return size; >>>>> } >>>>> static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, >>>>> unsigned long iova, size_t size, int lvl, >>>>> - arm_lpae_iopte *ptep) >>>>> + arm_lpae_iopte *ptep, int strict) >>>>> { >>>>> arm_lpae_iopte pte; >>>>> struct io_pgtable *iop = &data->iop; >>>>> @@ -609,7 +612,7 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, >>>>> io_pgtable_tlb_sync(iop); >>>>> ptep = iopte_deref(pte, data); >>>>> __arm_lpae_free_pgtable(data, lvl + 1, ptep); >>>>> - } else { >>>>> + } else if (strict) { >>>>> io_pgtable_tlb_add_flush(iop, iova, size, size, true); >>>>> } >>>>> @@ -620,25 +623,27 @@ static size_t __arm_lpae_unmap(struct arm_lpae_io_pgtable *data, >>>>> * minus the part we want to unmap >>>>> */ >>>>> return arm_lpae_split_blk_unmap(data, iova, size, pte, >>>>> - lvl + 1, ptep); >>>>> + lvl + 1, ptep, strict); >>>>> } >>>>> /* Keep on walkin' */ >>>>> ptep = iopte_deref(pte, data); >>>>> - return __arm_lpae_unmap(data, iova, size, lvl + 1, ptep); >>>>> + return __arm_lpae_unmap(data, iova, size, lvl + 1, ptep, strict); >>>>> } >>>>> static size_t arm_lpae_unmap(struct io_pgtable_ops *ops, unsigned long iova, >>>>> size_t size) >>>>> { >>>>> + int strict = ((iova & IOMMU_STRICT_MODE_MASK) == IOMMU_STRICT); >>>>> struct arm_lpae_io_pgtable *data = io_pgtable_ops_to_data(ops); >>>>> arm_lpae_iopte *ptep = data->pgd; >>>>> int lvl = ARM_LPAE_START_LVL(data); >>>>> + iova &= ~IOMMU_STRICT_MODE_MASK; >>>>> if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias))) >>>>> return 0; >>>>> - return __arm_lpae_unmap(data, iova, size, lvl, ptep); >>>>> + return __arm_lpae_unmap(data, iova, size, lvl, ptep, strict); >>>>> } >>>>> static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops, >>>>> >>>> >>>> . >>>> >>> >> _______________________________________________ >> iommu mailing list >> iommu@lists.linux-foundation.org >> https://lists.linuxfoundation.org/mailman/listinfo/iommu >> > > > . >
-- Thanks! BestRegards
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