From patchwork Wed Oct 21 03:20:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Kardashevskiy X-Patchwork-Id: 1385313 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 4CGGM74Sdcz9sSC for ; Wed, 21 Oct 2020 14:34:27 +1100 (AEDT) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ozlabs.ru Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4CGGM61hdczDqRh for ; Wed, 21 Oct 2020 14:34:26 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.ru (client-ip=107.174.27.60; helo=ozlabs.ru; envelope-from=aik@ozlabs.ru; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ozlabs.ru Received: from ozlabs.ru (ozlabs.ru [107.174.27.60]) by lists.ozlabs.org (Postfix) with ESMTP id 4CGGFn104QzDqcy for ; Wed, 21 Oct 2020 14:29:48 +1100 (AEDT) Received: from fstn1-p1.ozlabs.ibm.com (localhost [IPv6:::1]) by ozlabs.ru (Postfix) with ESMTP id AE9F0AE80252; Tue, 20 Oct 2020 23:20:00 -0400 (EDT) From: Alexey Kardashevskiy To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH kernel 2/2] powerpc/dma: Fallback to dma_ops when persistent memory present Date: Wed, 21 Oct 2020 14:20:26 +1100 Message-Id: <20201021032026.45030-3-aik@ozlabs.ru> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20201021032026.45030-1-aik@ozlabs.ru> References: <20201021032026.45030-1-aik@ozlabs.ru> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , Christoph Hellwig , linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" So far we have been using huge DMA windows to map all the RAM available. The RAM is normally mapped to the VM address space contiguously, and there is always a reasonable upper limit for possible future hot plugged RAM which makes it easy to map all RAM via IOMMU. Now there is persistent memory ("ibm,pmemory" in the FDT) which (unlike normal RAM) can map anywhere in the VM space beyond the maximum RAM size and since it can be used for DMA, it requires extending the huge window up to MAX_PHYSMEM_BITS which requires hypervisor support for: 1. huge TCE tables; 2. multilevel TCE tables; 3. huge IOMMU pages. Certain hypervisors cannot do either so the only option left is restricting the huge DMA window to include only RAM and fallback to the default DMA window for persistent memory. This checks if the system has persistent memory. If it does not, the DMA bypass mode is selected, i.e. * dev->bus_dma_limit = 0 * dev->dma_ops_bypass = true <- this avoid calling dma_ops for mapping. If there is such memory, this creates identity mapping only for RAM and disables the DMA bypass mode which makes generic DMA code use indirect dma_ops which may have performance impact: * dev->bus_dma_limit = bus_offset + max_ram_size for example 0x0800.0000.8000.0000 for a 2GB VM * dev->dma_ops_bypass = false <- this forces indirect calls to dma_ops for every mapping which then directs these to small or huge window. This should not change the existing behaviour when no persistent memory. Signed-off-by: Alexey Kardashevskiy --- Without reverting 19c65c3d30bb5a97170, I could have added I can repost if this is preferrable. Thanks. --- Changelog: v2: * rebased on current upstream with the device::bypass added and DMA direct code movement reverted --- arch/powerpc/kernel/dma-iommu.c | 68 +++++++++++++++++++++++++- arch/powerpc/platforms/pseries/iommu.c | 41 +++++++++++++--- 2 files changed, 99 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c index a1c744194018..9a2a3b95f72d 100644 --- a/arch/powerpc/kernel/dma-iommu.c +++ b/arch/powerpc/kernel/dma-iommu.c @@ -10,6 +10,16 @@ #include #include +static inline bool can_map_direct(struct device *dev, phys_addr_t addr) +{ + return dev->bus_dma_limit >= phys_to_dma(dev, addr); +} + +static inline bool dma_handle_direct(struct device *dev, dma_addr_t dma_handle) +{ + return dma_handle >= dev->archdata.dma_offset; +} + /* * Generic iommu implementation */ @@ -44,6 +54,12 @@ static dma_addr_t dma_iommu_map_page(struct device *dev, struct page *page, enum dma_data_direction direction, unsigned long attrs) { + if (dev->bus_dma_limit && + can_map_direct(dev, (phys_addr_t) page_to_phys(page) + + offset + size)) + return dma_direct_map_page(dev, page, offset, size, direction, + attrs); + return iommu_map_page(dev, get_iommu_table_base(dev), page, offset, size, dma_get_mask(dev), direction, attrs); } @@ -53,6 +69,12 @@ static void dma_iommu_unmap_page(struct device *dev, dma_addr_t dma_handle, size_t size, enum dma_data_direction direction, unsigned long attrs) { + if (dev->bus_dma_limit && + dma_handle_direct(dev, dma_handle + size)) { + dma_direct_unmap_page(dev, dma_handle, size, direction, attrs); + return; + } + iommu_unmap_page(get_iommu_table_base(dev), dma_handle, size, direction, attrs); } @@ -62,6 +84,22 @@ static int dma_iommu_map_sg(struct device *dev, struct scatterlist *sglist, int nelems, enum dma_data_direction direction, unsigned long attrs) { + if (dev->bus_dma_limit) { + struct scatterlist *s; + bool direct = true; + int i; + + for_each_sg(sglist, s, nelems, i) { + direct = can_map_direct(dev, + sg_phys(s) + s->offset + s->length); + if (!direct) + break; + } + if (direct) + return dma_direct_map_sg(dev, sglist, nelems, direction, + attrs); + } + return ppc_iommu_map_sg(dev, get_iommu_table_base(dev), sglist, nelems, dma_get_mask(dev), direction, attrs); } @@ -70,6 +108,24 @@ static void dma_iommu_unmap_sg(struct device *dev, struct scatterlist *sglist, int nelems, enum dma_data_direction direction, unsigned long attrs) { + if (dev->bus_dma_limit) { + struct scatterlist *s; + bool direct = true; + int i; + + for_each_sg(sglist, s, nelems, i) { + direct = dma_handle_direct(dev, + s->dma_address + s->length); + if (!direct) + break; + } + if (direct) { + dma_direct_unmap_sg(dev, sglist, nelems, direction, + attrs); + return; + } + } + ppc_iommu_unmap_sg(get_iommu_table_base(dev), sglist, nelems, direction, attrs); } @@ -90,8 +146,16 @@ int dma_iommu_dma_supported(struct device *dev, u64 mask) struct iommu_table *tbl = get_iommu_table_base(dev); if (dev_is_pci(dev) && dma_iommu_bypass_supported(dev, mask)) { - dev->dma_ops_bypass = true; - dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n"); + /* + * dma_iommu_bypass_supported() sets dma_max when there is + * 1:1 mapping but it is somehow limited. + * ibm,pmemory is one example. + */ + dev->dma_ops_bypass = dev->bus_dma_limit == 0; + if (!dev->dma_ops_bypass) + dev_warn(dev, "iommu: 64-bit OK but using default ops\n"); + else + dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n"); return 1; } diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c index e4198700ed1a..e6aa6c923666 100644 --- a/arch/powerpc/platforms/pseries/iommu.c +++ b/arch/powerpc/platforms/pseries/iommu.c @@ -839,7 +839,7 @@ static void remove_ddw(struct device_node *np, bool remove_prop) np, ret); } -static u64 find_existing_ddw(struct device_node *pdn) +static u64 find_existing_ddw(struct device_node *pdn, int *window_shift) { struct direct_window *window; const struct dynamic_dma_window_prop *direct64; @@ -851,6 +851,7 @@ static u64 find_existing_ddw(struct device_node *pdn) if (window->device == pdn) { direct64 = window->prop; dma_addr = be64_to_cpu(direct64->dma_base); + *window_shift = be32_to_cpu(direct64->window_shift); break; } } @@ -1111,11 +1112,13 @@ static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn) */ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) { - int len, ret; + int len = 0, ret; + bool pmem_present = of_find_node_by_type(NULL, "ibm,pmemory") != NULL; + int max_ram_len = order_base_2(ddw_memory_hotplug_max()); struct ddw_query_response query; struct ddw_create_response create; int page_shift; - u64 dma_addr, max_addr; + u64 dma_addr; struct device_node *dn; u32 ddw_avail[DDW_APPLICABLE_SIZE]; struct direct_window *window; @@ -1126,7 +1129,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) mutex_lock(&direct_window_init_mutex); - dma_addr = find_existing_ddw(pdn); + dma_addr = find_existing_ddw(pdn, &len); if (dma_addr != 0) goto out_unlock; @@ -1212,14 +1215,27 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) } /* verify the window * number of ptes will map the partition */ /* check largest block * page size > max memory hotplug addr */ - max_addr = ddw_memory_hotplug_max(); - if (query.largest_available_block < (max_addr >> page_shift)) { + /* + * The "ibm,pmemory" can appear anywhere in the address space. + * Assuming it is still backed by page structs, try MAX_PHYSMEM_BITS + * for the upper limit and fallback to max RAM otherwise but this + * disables device::dma_ops_bypass. + */ + len = max_ram_len; + if (pmem_present) { + if (query.largest_available_block >= + (1ULL << (MAX_PHYSMEM_BITS - page_shift))) + len = MAX_PHYSMEM_BITS - page_shift; + else + dev_info(&dev->dev, "Skipping ibm,pmemory"); + } + + if (query.largest_available_block < (1ULL << (len - page_shift))) { dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu " - "%llu-sized pages\n", max_addr, query.largest_available_block, + "%llu-sized pages\n", 1ULL << len, query.largest_available_block, 1ULL << page_shift); goto out_failed; } - len = order_base_2(max_addr); win64 = kzalloc(sizeof(struct property), GFP_KERNEL); if (!win64) { dev_info(&dev->dev, @@ -1299,6 +1315,15 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) out_unlock: mutex_unlock(&direct_window_init_mutex); + + /* + * If we have persistent memory and the window size is only as big + * as RAM, then we failed to create a window to cover persistent + * memory and need to set the DMA limit. + */ + if (pmem_present && dma_addr && (len == max_ram_len)) + dev->dev.bus_dma_limit = dma_addr + (1ULL << len); + return dma_addr; }