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[35.189.192.250]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-496c4632263sm89342385e9.15.2026.07.28.07.30.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 07:30:38 -0700 (PDT) Date: Tue, 28 Jul 2026 14:30:32 +0000 From: Mostafa Saleh To: "Aneesh Kumar K.V (Arm)" Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , x86@kernel.org, Jason Gunthorpe , Jiri Pirko , Michael Kelley Subject: Re: [PATCH v8 15/23] dma-direct: pass attrs to dma_capable() for DMA_ATTR_CC_SHARED checks Message-ID: References: <20260717180442.110954-1-aneesh.kumar@kernel.org> <20260717180442.110954-16-aneesh.kumar@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260717180442.110954-16-aneesh.kumar@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260728_073041_608256_D2F6F7C7 X-CRM114-Status: GOOD ( 31.81 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jul 17, 2026 at 11:34:33PM +0530, Aneesh Kumar K.V (Arm) wrote: > Teach dma_capable() about DMA_ATTR_CC_SHARED so the capability > check can reject encrypted DMA addresses for devices that require > unencrypted/shared DMA. > > Also propagate DMA_ATTR_CC_SHARED in swiotlb_map() when the selected > SWIOTLB pool is decrypted so the capability check sees the correct DMA > address attribute. > > Reviewed-by: Jason Gunthorpe > Tested-by: Jiri Pirko > Tested-by: Michael Kelley > Tested-by: Mostafa Saleh > Reviewed-by: Petr Tesarik > Signed-off-by: Aneesh Kumar K.V (Arm) > --- > arch/x86/kernel/amd_gart_64.c | 30 ++++++++++++++++-------------- > drivers/xen/swiotlb-xen.c | 6 +++--- > include/linux/dma-direct.h | 10 +++++++++- > kernel/dma/direct.h | 6 +++--- > kernel/dma/swiotlb.c | 2 +- > 5 files changed, 32 insertions(+), 22 deletions(-) > > diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c > index e8000a56732e..b5f1f031d45b 100644 > --- a/arch/x86/kernel/amd_gart_64.c > +++ b/arch/x86/kernel/amd_gart_64.c > @@ -180,22 +180,23 @@ static void iommu_full(struct device *dev, size_t size, int dir) > } > > static inline int > -need_iommu(struct device *dev, unsigned long addr, size_t size) > +need_iommu(struct device *dev, unsigned long addr, size_t size, unsigned long attrs) > { > - return force_iommu || !dma_capable(dev, addr, size, true); > + return force_iommu || !dma_capable(dev, addr, size, true, attrs); > } > > static inline int > -nonforced_iommu(struct device *dev, unsigned long addr, size_t size) > +nonforced_iommu(struct device *dev, unsigned long addr, size_t size, > + unsigned long attrs) > { > - return !dma_capable(dev, addr, size, true); > + return !dma_capable(dev, addr, size, true, attrs); > } > > /* Map a single continuous physical area into the IOMMU. > * Caller needs to check if the iommu is needed and flush. > */ > static dma_addr_t dma_map_area(struct device *dev, dma_addr_t phys_mem, > - size_t size, int dir, unsigned long align_mask) > + size_t size, int dir, unsigned long align_mask, unsigned long attrs) > { > unsigned long npages = iommu_num_pages(phys_mem, size, PAGE_SIZE); > unsigned long iommu_page; > @@ -206,7 +207,7 @@ static dma_addr_t dma_map_area(struct device *dev, dma_addr_t phys_mem, > > iommu_page = alloc_iommu(dev, npages, align_mask); > if (iommu_page == -1) { > - if (!nonforced_iommu(dev, phys_mem, size)) > + if (!nonforced_iommu(dev, phys_mem, size, attrs)) > return phys_mem; > if (panic_on_overflow) > panic("dma_map_area overflow %lu bytes\n", size); > @@ -231,10 +232,10 @@ static dma_addr_t gart_map_phys(struct device *dev, phys_addr_t paddr, > if (unlikely(attrs & DMA_ATTR_MMIO)) > return DMA_MAPPING_ERROR; > > - if (!need_iommu(dev, paddr, size)) > + if (!need_iommu(dev, paddr, size, attrs)) > return paddr; > > - bus = dma_map_area(dev, paddr, size, dir, 0); > + bus = dma_map_area(dev, paddr, size, dir, 0, attrs); > flush_gart(); > > return bus; > @@ -289,7 +290,7 @@ static void gart_unmap_sg(struct device *dev, struct scatterlist *sg, int nents, > > /* Fallback for dma_map_sg in case of overflow */ > static int dma_map_sg_nonforce(struct device *dev, struct scatterlist *sg, > - int nents, int dir) > + int nents, int dir, unsigned long attrs) > { > struct scatterlist *s; > int i; > @@ -301,8 +302,8 @@ static int dma_map_sg_nonforce(struct device *dev, struct scatterlist *sg, > for_each_sg(sg, s, nents, i) { > unsigned long addr = sg_phys(s); > > - if (nonforced_iommu(dev, addr, s->length)) { > - addr = dma_map_area(dev, addr, s->length, dir, 0); > + if (nonforced_iommu(dev, addr, s->length, attrs)) { > + addr = dma_map_area(dev, addr, s->length, dir, 0, attrs); > if (addr == DMA_MAPPING_ERROR) { > if (i > 0) > gart_unmap_sg(dev, sg, i, dir, 0); > @@ -401,7 +402,7 @@ static int gart_map_sg(struct device *dev, struct scatterlist *sg, int nents, > s->dma_address = addr; > BUG_ON(s->length == 0); > > - nextneed = need_iommu(dev, addr, s->length); > + nextneed = need_iommu(dev, addr, s->length, attrs); > > /* Handle the previous not yet processed entries */ > if (i > start) { > @@ -449,7 +450,7 @@ static int gart_map_sg(struct device *dev, struct scatterlist *sg, int nents, > > /* When it was forced or merged try again in a dumb way */ > if (force_iommu || iommu_merge) { > - out = dma_map_sg_nonforce(dev, sg, nents, dir); > + out = dma_map_sg_nonforce(dev, sg, nents, dir, attrs); > if (out > 0) > return out; > } > @@ -473,7 +474,8 @@ gart_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_addr, > return vaddr; > > *dma_addr = dma_map_area(dev, virt_to_phys(vaddr), size, > - DMA_BIDIRECTIONAL, (1UL << get_order(size)) - 1); > + DMA_BIDIRECTIONAL, > + (1UL << get_order(size)) - 1, attrs); > flush_gart(); > if (unlikely(*dma_addr == DMA_MAPPING_ERROR)) > goto out_free; > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > index 8c4abe65cd49..e2538824ef52 100644 > --- a/drivers/xen/swiotlb-xen.c > +++ b/drivers/xen/swiotlb-xen.c > @@ -212,7 +212,7 @@ static dma_addr_t xen_swiotlb_map_phys(struct device *dev, phys_addr_t phys, > BUG_ON(dir == DMA_NONE); > > if (attrs & DMA_ATTR_MMIO) { > - if (unlikely(!dma_capable(dev, phys, size, false))) { > + if (unlikely(!dma_capable(dev, phys, size, false, attrs))) { > dev_err_once( > dev, > "DMA addr %pa+%zu overflow (mask %llx, bus limit %llx).\n", > @@ -231,7 +231,7 @@ static dma_addr_t xen_swiotlb_map_phys(struct device *dev, phys_addr_t phys, > * we can safely return the device addr and not worry about bounce > * buffering it. > */ > - if (dma_capable(dev, dev_addr, size, true) && > + if (dma_capable(dev, dev_addr, size, true, attrs) && > !dma_kmalloc_needs_bounce(dev, size, dir) && > !range_straddles_page_boundary(phys, size) && > !xen_arch_need_swiotlb(dev, phys, dev_addr) && > @@ -253,7 +253,7 @@ static dma_addr_t xen_swiotlb_map_phys(struct device *dev, phys_addr_t phys, > /* > * Ensure that the address returned is DMA'ble > */ > - if (unlikely(!dma_capable(dev, dev_addr, size, true))) { > + if (unlikely(!dma_capable(dev, dev_addr, size, true, attrs))) { > __swiotlb_tbl_unmap_single(dev, map, size, dir, > attrs | DMA_ATTR_SKIP_CPU_SYNC, > swiotlb_find_pool(dev, map)); > diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h > index 94fad4e7c11e..daa31a1adf7b 100644 > --- a/include/linux/dma-direct.h > +++ b/include/linux/dma-direct.h > @@ -135,12 +135,20 @@ static inline bool force_dma_unencrypted(struct device *dev) > #endif /* CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED */ > > static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size, > - bool is_ram) > + bool is_ram, unsigned long attrs) > { > dma_addr_t end = addr + size - 1; > > if (addr == DMA_MAPPING_ERROR) > return false; > + /* > + * The DMA address was derived from encrypted RAM, but this device > + * requires unencrypted DMA addresses. Treat it as not DMA-capable > + * so the caller can fall back to a suitable SWIOTLB pool. > + */ > + if (!(attrs & DMA_ATTR_CC_SHARED) && force_dma_unencrypted(dev)) > + return false; > + I guess it does not make sense to check the other way? I'd be worried if some a confidential device uses shared memory which might leak info. Thanks, Mostafa > if (is_ram && !IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) && > min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn))) > return false; > diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h > index 7140c208c123..e05dc7649366 100644 > --- a/kernel/dma/direct.h > +++ b/kernel/dma/direct.h > @@ -101,15 +101,15 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev, > > if (attrs & DMA_ATTR_MMIO) { > dma_addr = phys; > - if (unlikely(!dma_capable(dev, dma_addr, size, false))) > + if (unlikely(!dma_capable(dev, dma_addr, size, false, attrs))) > goto err_overflow; > } else if (attrs & DMA_ATTR_CC_SHARED) { > dma_addr = phys_to_dma_unencrypted(dev, phys); > - if (unlikely(!dma_capable(dev, dma_addr, size, false))) > + if (unlikely(!dma_capable(dev, dma_addr, size, false, attrs))) > goto err_overflow; > } else { > dma_addr = phys_to_dma(dev, phys); > - if (unlikely(!dma_capable(dev, dma_addr, size, true)) || > + if (unlikely(!dma_capable(dev, dma_addr, size, true, attrs)) || > dma_kmalloc_needs_bounce(dev, size, dir)) { > if (is_swiotlb_active(dev) && > !(attrs & DMA_ATTR_REQUIRE_COHERENT)) > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 335e27bc1e1f..b5960c2e98d8 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -1697,7 +1697,7 @@ dma_addr_t swiotlb_map(struct device *dev, phys_addr_t paddr, size_t size, > else > dma_addr = phys_to_dma_encrypted(dev, swiotlb_addr); > > - if (unlikely(!dma_capable(dev, dma_addr, size, true))) { > + if (unlikely(!dma_capable(dev, dma_addr, size, true, attrs))) { > __swiotlb_tbl_unmap_single(dev, swiotlb_addr, size, dir, > attrs | DMA_ATTR_SKIP_CPU_SYNC, > swiotlb_find_pool(dev, swiotlb_addr)); > -- > 2.43.0 >