| Message ID | 1654507822-168026-3-git-send-email-john.garry@huawei.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | DMA mapping changes for SCSI core | expand |
On 6/6/22 02:30, John Garry via iommu wrote: > +unsigned long iova_rcache_range(void) > +{ > + return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1); > +} My understanding is that iova cache entries may be smaller than IOVA_RANGE_CACHE_MAX_SIZE and hence that even if code that uses the DMA mapping API respects this limit that a cache miss can still happen. Thanks, Bart.
On 08/06/2022 18:26, Bart Van Assche wrote: > On 6/6/22 02:30, John Garry via iommu wrote: >> +unsigned long iova_rcache_range(void) >> +{ >> + return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1); >> +} > > My understanding is that iova cache entries may be smaller than > IOVA_RANGE_CACHE_MAX_SIZE and hence that even if code that uses the DMA > mapping API respects this limit that a cache miss can still happen. Sure, a cache miss may still happen - however once we have stressed the system for a while then the rcaches fill up and don't fail often, or often enough to be noticeable compared to not having a cached IOVAs at all. Thanks, john
On 06/06/2022 10:30, John Garry wrote: > Add the IOMMU callback for DMA mapping API dma_opt_mapping_size(), which > allows the drivers to know the optimal mapping limit and thus limit the > requested IOVA lengths. > > This value is based on the IOVA rcache range limit, as IOVAs allocated > above this limit must always be newly allocated, which may be quite slow. > Can I please get some sort of ack from the IOMMU people on this one? Thanks, John EOM > Signed-off-by: John Garry <john.garry@huawei.com> > Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> > --- > drivers/iommu/dma-iommu.c | 6 ++++++ > drivers/iommu/iova.c | 5 +++++ > include/linux/iova.h | 2 ++ > 3 files changed, 13 insertions(+) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index f90251572a5d..9e1586447ee8 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -1459,6 +1459,11 @@ static unsigned long iommu_dma_get_merge_boundary(struct device *dev) > return (1UL << __ffs(domain->pgsize_bitmap)) - 1; > } > > +static size_t iommu_dma_opt_mapping_size(void) > +{ > + return iova_rcache_range(); > +} > + > static const struct dma_map_ops iommu_dma_ops = { > .alloc = iommu_dma_alloc, > .free = iommu_dma_free, > @@ -1479,6 +1484,7 @@ static const struct dma_map_ops iommu_dma_ops = { > .map_resource = iommu_dma_map_resource, > .unmap_resource = iommu_dma_unmap_resource, > .get_merge_boundary = iommu_dma_get_merge_boundary, > + .opt_mapping_size = iommu_dma_opt_mapping_size, > }; > > /* > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c > index db77aa675145..9f00b58d546e 100644 > --- a/drivers/iommu/iova.c > +++ b/drivers/iommu/iova.c > @@ -26,6 +26,11 @@ static unsigned long iova_rcache_get(struct iova_domain *iovad, > static void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad); > static void free_iova_rcaches(struct iova_domain *iovad); > > +unsigned long iova_rcache_range(void) > +{ > + return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1); > +} > + > static int iova_cpuhp_dead(unsigned int cpu, struct hlist_node *node) > { > struct iova_domain *iovad; > diff --git a/include/linux/iova.h b/include/linux/iova.h > index 320a70e40233..c6ba6d95d79c 100644 > --- a/include/linux/iova.h > +++ b/include/linux/iova.h > @@ -79,6 +79,8 @@ static inline unsigned long iova_pfn(struct iova_domain *iovad, dma_addr_t iova) > int iova_cache_get(void); > void iova_cache_put(void); > > +unsigned long iova_rcache_range(void); > + > void free_iova(struct iova_domain *iovad, unsigned long pfn); > void __free_iova(struct iova_domain *iovad, struct iova *iova); > struct iova *alloc_iova(struct iova_domain *iovad, unsigned long size,
On 14/06/2022 14:12, John Garry wrote: > On 06/06/2022 10:30, John Garry wrote: >> Add the IOMMU callback for DMA mapping API dma_opt_mapping_size(), which >> allows the drivers to know the optimal mapping limit and thus limit the >> requested IOVA lengths. >> >> This value is based on the IOVA rcache range limit, as IOVAs allocated >> above this limit must always be newly allocated, which may be quite slow. >> > > Can I please get some sort of ack from the IOMMU people on this one? > Another request for an ack please. Thanks, john > >> Signed-off-by: John Garry <john.garry@huawei.com> >> Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> >> --- >> drivers/iommu/dma-iommu.c | 6 ++++++ >> drivers/iommu/iova.c | 5 +++++ >> include/linux/iova.h | 2 ++ >> 3 files changed, 13 insertions(+) >> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >> index f90251572a5d..9e1586447ee8 100644 >> --- a/drivers/iommu/dma-iommu.c >> +++ b/drivers/iommu/dma-iommu.c >> @@ -1459,6 +1459,11 @@ static unsigned long >> iommu_dma_get_merge_boundary(struct device *dev) >> return (1UL << __ffs(domain->pgsize_bitmap)) - 1; >> } >> +static size_t iommu_dma_opt_mapping_size(void) >> +{ >> + return iova_rcache_range(); >> +} >> + >> static const struct dma_map_ops iommu_dma_ops = { >> .alloc = iommu_dma_alloc, >> .free = iommu_dma_free, >> @@ -1479,6 +1484,7 @@ static const struct dma_map_ops iommu_dma_ops = { >> .map_resource = iommu_dma_map_resource, >> .unmap_resource = iommu_dma_unmap_resource, >> .get_merge_boundary = iommu_dma_get_merge_boundary, >> + .opt_mapping_size = iommu_dma_opt_mapping_size, >> }; >> /* >> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c >> index db77aa675145..9f00b58d546e 100644 >> --- a/drivers/iommu/iova.c >> +++ b/drivers/iommu/iova.c >> @@ -26,6 +26,11 @@ static unsigned long iova_rcache_get(struct >> iova_domain *iovad, >> static void free_cpu_cached_iovas(unsigned int cpu, struct >> iova_domain *iovad); >> static void free_iova_rcaches(struct iova_domain *iovad); >> +unsigned long iova_rcache_range(void) >> +{ >> + return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1); >> +} >> + >> static int iova_cpuhp_dead(unsigned int cpu, struct hlist_node *node) >> { >> struct iova_domain *iovad; >> diff --git a/include/linux/iova.h b/include/linux/iova.h >> index 320a70e40233..c6ba6d95d79c 100644 >> --- a/include/linux/iova.h >> +++ b/include/linux/iova.h >> @@ -79,6 +79,8 @@ static inline unsigned long iova_pfn(struct >> iova_domain *iovad, dma_addr_t iova) >> int iova_cache_get(void); >> void iova_cache_put(void); >> +unsigned long iova_rcache_range(void); >> + >> void free_iova(struct iova_domain *iovad, unsigned long pfn); >> void __free_iova(struct iova_domain *iovad, struct iova *iova); >> struct iova *alloc_iova(struct iova_domain *iovad, unsigned long size, >
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index f90251572a5d..9e1586447ee8 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -1459,6 +1459,11 @@ static unsigned long iommu_dma_get_merge_boundary(struct device *dev) return (1UL << __ffs(domain->pgsize_bitmap)) - 1; } +static size_t iommu_dma_opt_mapping_size(void) +{ + return iova_rcache_range(); +} + static const struct dma_map_ops iommu_dma_ops = { .alloc = iommu_dma_alloc, .free = iommu_dma_free, @@ -1479,6 +1484,7 @@ static const struct dma_map_ops iommu_dma_ops = { .map_resource = iommu_dma_map_resource, .unmap_resource = iommu_dma_unmap_resource, .get_merge_boundary = iommu_dma_get_merge_boundary, + .opt_mapping_size = iommu_dma_opt_mapping_size, }; /* diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index db77aa675145..9f00b58d546e 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -26,6 +26,11 @@ static unsigned long iova_rcache_get(struct iova_domain *iovad, static void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad); static void free_iova_rcaches(struct iova_domain *iovad); +unsigned long iova_rcache_range(void) +{ + return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1); +} + static int iova_cpuhp_dead(unsigned int cpu, struct hlist_node *node) { struct iova_domain *iovad; diff --git a/include/linux/iova.h b/include/linux/iova.h index 320a70e40233..c6ba6d95d79c 100644 --- a/include/linux/iova.h +++ b/include/linux/iova.h @@ -79,6 +79,8 @@ static inline unsigned long iova_pfn(struct iova_domain *iovad, dma_addr_t iova) int iova_cache_get(void); void iova_cache_put(void); +unsigned long iova_rcache_range(void); + void free_iova(struct iova_domain *iovad, unsigned long pfn); void __free_iova(struct iova_domain *iovad, struct iova *iova); struct iova *alloc_iova(struct iova_domain *iovad, unsigned long size,