Messages in this thread Patch in this message |  | | Subject | Re: [rfc] dma-mapping: preallocate unencrypted DMA atomic pool | From | Robin Murphy <> | Date | Mon, 6 Jan 2020 17:34:00 +0000 |
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On 01/01/2020 1:54 am, David Rientjes via iommu wrote: > Christoph, Thomas, is something like this (without the diagnosic > information included in this patch) acceptable for these allocations? > Adding expansion support when the pool is half depleted wouldn't be *that* > hard. > > Or are there alternatives we should consider? Thanks!
Are there any platforms which require both non-cacheable remapping *and* unencrypted remapping for distinct subsets of devices?
If not (and I'm assuming there aren't, because otherwise this patch is incomplete in covering only 2 of the 3 possible combinations), then couldn't we keep things simpler by just attributing both properties to the single "atomic pool" on the basis that one or the other will always be a no-op? In other words, basically just tweaking the existing "!coherent" tests to "!coherent || force_dma_unencrypted()" and doing set_dma_unencrypted() unconditionally in atomic_pool_init().
Robin.
> When AMD SEV is enabled in the guest, all allocations through > dma_pool_alloc_page() must call set_memory_decrypted() for unencrypted > DMA. This includes dma_pool_alloc() and dma_direct_alloc_pages(). These > calls may block which is not allowed in atomic allocation contexts such as > from the NVMe driver. > > Preallocate a complementary unecrypted DMA atomic pool that is initially > 4MB in size. This patch does not contain dynamic expansion, but that > could be added if necessary. > > In our stress testing, our peak unecrypted DMA atomic allocation > requirements is ~1.4MB, so 4MB is plenty. This pool is similar to the > existing DMA atomic pool but is unencrypted. > > Signed-off-by: David Rientjes <rientjes@google.com> > --- > Based on v5.4 HEAD. > > This commit contains diagnostic information and is not intended for use > in a production environment. > > arch/x86/Kconfig | 1 + > drivers/iommu/dma-iommu.c | 5 +- > include/linux/dma-mapping.h | 7 ++- > kernel/dma/direct.c | 16 ++++- > kernel/dma/remap.c | 116 ++++++++++++++++++++++++++---------- > 5 files changed, 108 insertions(+), 37 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1530,6 +1530,7 @@ config X86_CPA_STATISTICS > config AMD_MEM_ENCRYPT > bool "AMD Secure Memory Encryption (SME) support" > depends on X86_64 && CPU_SUP_AMD > + select DMA_DIRECT_REMAP > select DYNAMIC_PHYSICAL_MASK > select ARCH_USE_MEMREMAP_PROT > select ARCH_HAS_FORCE_DMA_UNENCRYPTED > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -928,7 +928,7 @@ static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr) > > /* Non-coherent atomic allocation? Easy */ > if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && > - dma_free_from_pool(cpu_addr, alloc_size)) > + dma_free_from_pool(dev, cpu_addr, alloc_size)) > return; > > if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) { > @@ -1011,7 +1011,8 @@ static void *iommu_dma_alloc(struct device *dev, size_t size, > > if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && > !gfpflags_allow_blocking(gfp) && !coherent) > - cpu_addr = dma_alloc_from_pool(PAGE_ALIGN(size), &page, gfp); > + cpu_addr = dma_alloc_from_pool(dev, PAGE_ALIGN(size), &page, > + gfp); > else > cpu_addr = iommu_dma_alloc_pages(dev, size, &page, gfp, attrs); > if (!cpu_addr) > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -629,9 +629,10 @@ void *dma_common_pages_remap(struct page **pages, size_t size, > pgprot_t prot, const void *caller); > void dma_common_free_remap(void *cpu_addr, size_t size); > > -bool dma_in_atomic_pool(void *start, size_t size); > -void *dma_alloc_from_pool(size_t size, struct page **ret_page, gfp_t flags); > -bool dma_free_from_pool(void *start, size_t size); > +bool dma_in_atomic_pool(struct device *dev, void *start, size_t size); > +void *dma_alloc_from_pool(struct device *dev, size_t size, > + struct page **ret_page, gfp_t flags); > +bool dma_free_from_pool(struct device *dev, void *start, size_t size); > > int > dma_common_get_sgtable(struct device *dev, struct sg_table *sgt, void *cpu_addr, > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -10,6 +10,7 @@ > #include <linux/dma-direct.h> > #include <linux/scatterlist.h> > #include <linux/dma-contiguous.h> > +#include <linux/dma-mapping.h> > #include <linux/dma-noncoherent.h> > #include <linux/pfn.h> > #include <linux/set_memory.h> > @@ -131,6 +132,13 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, > struct page *page; > void *ret; > > + if (!gfpflags_allow_blocking(gfp) && force_dma_unencrypted(dev)) { > + ret = dma_alloc_from_pool(dev, size, &page, gfp); > + if (!ret) > + return NULL; > + goto done; > + } > + > page = __dma_direct_alloc_pages(dev, size, dma_handle, gfp, attrs); > if (!page) > return NULL; > @@ -156,7 +164,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, > __dma_direct_free_pages(dev, size, page); > return NULL; > } > - > +done: > ret = page_address(page); > if (force_dma_unencrypted(dev)) { > set_memory_decrypted((unsigned long)ret, 1 << get_order(size)); > @@ -185,6 +193,12 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr, > { > unsigned int page_order = get_order(size); > > + if (force_dma_unencrypted(dev) && > + dma_in_atomic_pool(dev, cpu_addr, size)) { > + dma_free_from_pool(dev, cpu_addr, size); > + return; > + } > + > if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) && > !force_dma_unencrypted(dev)) { > /* cpu_addr is a struct page cookie, not a kernel address */ > diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c > --- a/kernel/dma/remap.c > +++ b/kernel/dma/remap.c > @@ -8,6 +8,7 @@ > #include <linux/dma-contiguous.h> > #include <linux/init.h> > #include <linux/genalloc.h> > +#include <linux/set_memory.h> > #include <linux/slab.h> > #include <linux/vmalloc.h> > > @@ -100,9 +101,11 @@ void dma_common_free_remap(void *cpu_addr, size_t size) > > #ifdef CONFIG_DMA_DIRECT_REMAP > static struct gen_pool *atomic_pool __ro_after_init; > +static struct gen_pool *atomic_pool_unencrypted __ro_after_init; > > #define DEFAULT_DMA_COHERENT_POOL_SIZE SZ_256K > static size_t atomic_pool_size __initdata = DEFAULT_DMA_COHERENT_POOL_SIZE; > +static size_t atomic_pool_unencrypted_size __initdata = SZ_4M; > > static int __init early_coherent_pool(char *p) > { > @@ -120,10 +123,11 @@ static gfp_t dma_atomic_pool_gfp(void) > return GFP_KERNEL; > } > > -static int __init dma_atomic_pool_init(void) > +static int __init __dma_atomic_pool_init(struct gen_pool **pool, > + size_t pool_size, bool unencrypt) > { > - unsigned int pool_size_order = get_order(atomic_pool_size); > - unsigned long nr_pages = atomic_pool_size >> PAGE_SHIFT; > + unsigned int pool_size_order = get_order(pool_size); > + unsigned long nr_pages = pool_size >> PAGE_SHIFT; > struct page *page; > void *addr; > int ret; > @@ -136,78 +140,128 @@ static int __init dma_atomic_pool_init(void) > if (!page) > goto out; > > - arch_dma_prep_coherent(page, atomic_pool_size); > + arch_dma_prep_coherent(page, pool_size); > > - atomic_pool = gen_pool_create(PAGE_SHIFT, -1); > - if (!atomic_pool) > + *pool = gen_pool_create(PAGE_SHIFT, -1); > + if (!*pool) > goto free_page; > > - addr = dma_common_contiguous_remap(page, atomic_pool_size, > + addr = dma_common_contiguous_remap(page, pool_size, > pgprot_dmacoherent(PAGE_KERNEL), > __builtin_return_address(0)); > if (!addr) > goto destroy_genpool; > > - ret = gen_pool_add_virt(atomic_pool, (unsigned long)addr, > - page_to_phys(page), atomic_pool_size, -1); > + ret = gen_pool_add_virt(*pool, (unsigned long)addr, page_to_phys(page), > + pool_size, -1); > if (ret) > goto remove_mapping; > - gen_pool_set_algo(atomic_pool, gen_pool_first_fit_order_align, NULL); > + gen_pool_set_algo(*pool, gen_pool_first_fit_order_align, NULL); > + if (unencrypt) > + set_memory_decrypted((unsigned long)page_to_virt(page), nr_pages); > > - pr_info("DMA: preallocated %zu KiB pool for atomic allocations\n", > - atomic_pool_size / 1024); > + pr_info("DMA: preallocated %zu KiB pool for atomic allocations%s\n", > + pool_size >> 10, unencrypt ? " (unencrypted)" : ""); > return 0; > > remove_mapping: > - dma_common_free_remap(addr, atomic_pool_size); > + dma_common_free_remap(addr, pool_size); > destroy_genpool: > - gen_pool_destroy(atomic_pool); > - atomic_pool = NULL; > + gen_pool_destroy(*pool); > + *pool = NULL; > free_page: > if (!dma_release_from_contiguous(NULL, page, nr_pages)) > __free_pages(page, pool_size_order); > out: > - pr_err("DMA: failed to allocate %zu KiB pool for atomic coherent allocation\n", > - atomic_pool_size / 1024); > + pr_err("DMA: failed to allocate %zu KiB pool for atomic coherent allocation%s\n", > + pool_size >> 10, unencrypt ? " (unencrypted)" : ""); > return -ENOMEM; > } > + > +static int __init dma_atomic_pool_init(void) > +{ > + int ret; > + > + ret = __dma_atomic_pool_init(&atomic_pool, atomic_pool_size, false); > + if (ret) > + return ret; > + return __dma_atomic_pool_init(&atomic_pool_unencrypted, > + atomic_pool_unencrypted_size, true); > +} > postcore_initcall(dma_atomic_pool_init); > > -bool dma_in_atomic_pool(void *start, size_t size) > +static inline struct gen_pool *dev_to_pool(struct device *dev) > { > - if (unlikely(!atomic_pool)) > - return false; > + if (force_dma_unencrypted(dev)) > + return atomic_pool_unencrypted; > + return atomic_pool; > +} > + > +bool dma_in_atomic_pool(struct device *dev, void *start, size_t size) > +{ > + struct gen_pool *pool = dev_to_pool(dev); > > - return addr_in_gen_pool(atomic_pool, (unsigned long)start, size); > + if (unlikely(!pool)) > + return false; > + return addr_in_gen_pool(pool, (unsigned long)start, size); > } > > -void *dma_alloc_from_pool(size_t size, struct page **ret_page, gfp_t flags) > +static struct gen_pool *atomic_pool __ro_after_init; > +static size_t encrypted_pool_size; > +static size_t encrypted_pool_size_max; > +static spinlock_t encrypted_pool_size_lock; > + > +void *dma_alloc_from_pool(struct device *dev, size_t size, > + struct page **ret_page, gfp_t flags) > { > + struct gen_pool *pool = dev_to_pool(dev); > unsigned long val; > void *ptr = NULL; > > - if (!atomic_pool) { > - WARN(1, "coherent pool not initialised!\n"); > + if (!pool) { > + WARN(1, "%scoherent pool not initialised!\n", > + force_dma_unencrypted(dev) ? "encrypted " : ""); > return NULL; > } > > - val = gen_pool_alloc(atomic_pool, size); > + val = gen_pool_alloc(pool, size); > if (val) { > - phys_addr_t phys = gen_pool_virt_to_phys(atomic_pool, val); > + phys_addr_t phys = gen_pool_virt_to_phys(pool, val); > > *ret_page = pfn_to_page(__phys_to_pfn(phys)); > ptr = (void *)val; > memset(ptr, 0, size); > + if (force_dma_unencrypted(dev)) { > + unsigned long flags; > + > + spin_lock_irqsave(&encrypted_pool_size_lock, flags); > + encrypted_pool_size += size; > + if (encrypted_pool_size > encrypted_pool_size_max) { > + encrypted_pool_size_max = encrypted_pool_size; > + pr_info("max encrypted pool size now %lu\n", > + encrypted_pool_size_max); > + } > + spin_unlock_irqrestore(&encrypted_pool_size_lock, flags); > + } > } > > return ptr; > } > > -bool dma_free_from_pool(void *start, size_t size) > +bool dma_free_from_pool(struct device *dev, void *start, size_t size) > { > - if (!dma_in_atomic_pool(start, size)) > + struct gen_pool *pool = dev_to_pool(dev); > + > + if (!dma_in_atomic_pool(dev, start, size)) > return false; > - gen_pool_free(atomic_pool, (unsigned long)start, size); > + gen_pool_free(pool, (unsigned long)start, size); > + if (force_dma_unencrypted(dev)) { > + unsigned long flags; > + > + spin_lock_irqsave(&encrypted_pool_size_lock, flags); > + encrypted_pool_size -= size; > + spin_unlock_irqrestore(&encrypted_pool_size_lock, flags); > + } > return true; > } > > @@ -220,7 +274,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, > size = PAGE_ALIGN(size); > > if (!gfpflags_allow_blocking(flags)) { > - ret = dma_alloc_from_pool(size, &page, flags); > + ret = dma_alloc_from_pool(dev, size, &page, flags); > if (!ret) > return NULL; > goto done; > @@ -251,7 +305,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, > void arch_dma_free(struct device *dev, size_t size, void *vaddr, > dma_addr_t dma_handle, unsigned long attrs) > { > - if (!dma_free_from_pool(vaddr, PAGE_ALIGN(size))) { > + if (!dma_free_from_pool(dev, vaddr, PAGE_ALIGN(size))) { > phys_addr_t phys = dma_to_phys(dev, dma_handle); > struct page *page = pfn_to_page(__phys_to_pfn(phys)); > > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu >
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