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 <[email protected]>
>>>>> ---
>>>>> 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,
>>>>>
>>>>
>>>> .
>>>>
>>>
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>>
>
>
> .
>
--
Thanks!
BestRegards
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