Messages in this thread | | | Subject | Re: [PATCHv2 1/3] iommu/io-pgtable: Add a quirk to use tlb_flush_all() for partial walk flush | From | Robin Murphy <> | Date | Mon, 21 Jun 2021 16:45:50 +0100 |
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On 2021-06-18 03:51, Sai Prakash Ranjan wrote: > Add a quirk IO_PGTABLE_QUIRK_TLB_INV_ALL to invalidate entire context > with tlb_flush_all() callback in partial walk flush to improve unmap > performance on select few platforms where the cost of over-invalidation > is less than the unmap latency.
I still think this doesn't belong anywhere near io-pgtable at all. It's a driver-internal decision how exactly it implements a non-leaf invalidation, and that may be more complex than a predetermined boolean decision. For example, I've just realised for SMMUv3 we can't invalidate multiple levels of table at once with a range command, since if we assume the whole thing is mapped at worst-case page granularity we may fail to invalidate any parts which are mapped as intermediate-level blocks. If invalidating a 1GB region (with 4KB granule) means having to fall back to 256K non-range commands, we may not want to invalidate by VA then, even though doing so for a 2MB region is still optimal.
It's also quite feasible that drivers might want to do this for leaf invalidations too - if you don't like issuing 512 commands to invalidate 2MB, do you like issuing 511 commands to invalidate 2044KB? - and at that point the logic really has to be in the driver anyway.
Robin.
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org> > --- > drivers/iommu/io-pgtable-arm.c | 3 ++- > include/linux/io-pgtable.h | 5 +++++ > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c > index 87def58e79b5..5d362f2214bd 100644 > --- a/drivers/iommu/io-pgtable-arm.c > +++ b/drivers/iommu/io-pgtable-arm.c > @@ -768,7 +768,8 @@ arm_64_lpae_alloc_pgtable_s1(struct io_pgtable_cfg *cfg, void *cookie) > if (cfg->quirks & ~(IO_PGTABLE_QUIRK_ARM_NS | > IO_PGTABLE_QUIRK_NON_STRICT | > IO_PGTABLE_QUIRK_ARM_TTBR1 | > - IO_PGTABLE_QUIRK_ARM_OUTER_WBWA)) > + IO_PGTABLE_QUIRK_ARM_OUTER_WBWA | > + IO_PGTABLE_QUIRK_TLB_INV_ALL)) > return NULL; > > data = arm_lpae_alloc_pgtable(cfg); > diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h > index 4d40dfa75b55..45441592a0e6 100644 > --- a/include/linux/io-pgtable.h > +++ b/include/linux/io-pgtable.h > @@ -82,6 +82,10 @@ struct io_pgtable_cfg { > * > * IO_PGTABLE_QUIRK_ARM_OUTER_WBWA: Override the outer-cacheability > * attributes set in the TCR for a non-coherent page-table walker. > + * > + * IO_PGTABLE_QUIRK_TLB_INV_ALL: Use TLBIALL/TLBIASID to invalidate > + * entire context for partial walk flush to increase unmap > + * performance on select few platforms. > */ > #define IO_PGTABLE_QUIRK_ARM_NS BIT(0) > #define IO_PGTABLE_QUIRK_NO_PERMS BIT(1) > @@ -89,6 +93,7 @@ struct io_pgtable_cfg { > #define IO_PGTABLE_QUIRK_NON_STRICT BIT(4) > #define IO_PGTABLE_QUIRK_ARM_TTBR1 BIT(5) > #define IO_PGTABLE_QUIRK_ARM_OUTER_WBWA BIT(6) > + #define IO_PGTABLE_QUIRK_TLB_INV_ALL BIT(7) > unsigned long quirks; > unsigned long pgsize_bitmap; > unsigned int ias; >
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