On 16/02/17 13:52, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <[email protected]>
>
> Do a check for already installed leaf entry at the current level before
> performing any actions when trying to map.
>
> This check is already present in arm_v7s_init_pte(), i.e. before
> installing new leaf entry at the current level if conditions to do so
> are met (num_entries > 0).
>
> But, this might be insufficient in case when we have already
> installed block mapping at this level and it is not time to
> install new leaf entry (num_entries == 0).
> In that case we continue walking the page table down with wrong pointer
> to the next level.
>
> So, move check from arm_v7s_init_pte() to __arm_v7s_map() in order to
> avoid all cases.
Would it not be more logical (and simpler) to just check that the thing
we dereference is valid to dereference when we dereference it? i.e.:
-----8<-----
diff --git a/drivers/iommu/io-pgtable-arm-v7s.c
b/drivers/iommu/io-pgtable-arm-v7s.c
index 0769276c0537..f3112f9ff494 100644
--- a/drivers/iommu/io-pgtable-arm-v7s.c
+++ b/drivers/iommu/io-pgtable-arm-v7s.c
@@ -418,8 +418,10 @@ static int __arm_v7s_map(struct arm_v7s_io_pgtable
*data, unsigned long iova,
pte |= ARM_V7S_ATTR_NS_TABLE;
__arm_v7s_set_pte(ptep, pte, 1, cfg);
- } else {
+ } else if (ARM_V7S_PTE_IS_TABLE(pte, lvl)) {
cptep = iopte_deref(pte, lvl);
+ } else {
+ return -EEXIST;
}
/* Rinse, repeat */
----->8-----
I think the equivalent could be done in LPAE as well.
Robin.
> Signed-off-by: Oleksandr Tyshchenko <[email protected]>
> ---
> This patch does similar things as the patch I have pushed a week ago
> for long-descriptor format [1].
> The reason why this patch is RFC is because I am not sure I did the right
> thing and I even didn't test it.
>
> [1]
> https://lists.linuxfoundation.org/pipermail/iommu/2017-February/020411.html
> ---
> ---
> drivers/iommu/io-pgtable-arm-v7s.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/io-pgtable-arm-v7s.c
> b/drivers/iommu/io-pgtable-arm-v7s.c
> index f50e51c..7f7594b 100644
> --- a/drivers/iommu/io-pgtable-arm-v7s.c
> +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> @@ -364,10 +364,6 @@ static int arm_v7s_init_pte(struct arm_v7s_io_pgtable
> *data,
> if (WARN_ON(__arm_v7s_unmap(data, iova + i * sz,
> sz, lvl, tblp) != sz))
> return -EINVAL;
> - } else if (ptep[i]) {
> - /* We require an unmap first */
> - WARN_ON(!selftest_running);
> - return -EEXIST;
> }
>
> pte |= ARM_V7S_PTE_TYPE_PAGE;
> @@ -392,11 +388,20 @@ static int __arm_v7s_map(struct arm_v7s_io_pgtable
> *data, unsigned long iova,
> {
> struct io_pgtable_cfg *cfg = &data->iop.cfg;
> arm_v7s_iopte pte, *cptep;
> - int num_entries = size >> ARM_V7S_LVL_SHIFT(lvl);
> + int i = 0, num_entries = size >> ARM_V7S_LVL_SHIFT(lvl);
>
> /* Find our entry at the current level */
> ptep += ARM_V7S_LVL_IDX(iova, lvl);
>
> + /* Check for already installed leaf entry */
> + do {
> + if (ptep[i] && !ARM_V7S_PTE_IS_TABLE(ptep[i], lvl)) {
> + /* We require an unmap first */
> + WARN_ON(!selftest_running);
> + return -EEXIST;
> + }
> + } while (++i < num_entries);
> +
> /* If we can install a leaf entry at this level, then do so */
> if (num_entries)
> return arm_v7s_init_pte(data, iova, paddr, prot,
>
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