![Mel Gorman](/assets/img/avatar_default.png)
__GFP_WAIT has been used to identify atomic context in callers that hold spinlocks or are in interrupts. They are expected to be high priority and have access one of two watermarks lower than "min" which can be referred to as the "atomic reserve". __GFP_HIGH users get access to the first lower watermark and can be called the "high priority reserve". Over time, callers had a requirement to not block when fallback options were available. Some have abused __GFP_WAIT leading to a situation where an optimisitic allocation with a fallback option can access atomic reserves. This patch uses __GFP_ATOMIC to identify callers that are truely atomic, cannot sleep and have no alternative. High priority users continue to use __GFP_HIGH. __GFP_DIRECT_RECLAIM identifies callers that can sleep and are willing to enter direct reclaim. __GFP_KSWAPD_RECLAIM to identify callers that want to wake kswapd for background reclaim. __GFP_WAIT is redefined as a caller that is willing to enter direct reclaim and wake kswapd for background reclaim. This patch then converts a number of sites o __GFP_ATOMIC is used by callers that are high priority and have memory pools for those requests. GFP_ATOMIC uses this flag. o Callers that have a limited mempool to guarantee forward progress clear __GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall into this category where kswapd will still be woken but atomic reserves are not used as there is a one-entry mempool to guarantee progress. o Callers that are checking if they are non-blocking should use the helper gfpflags_allow_blocking() where possible. This is because checking for __GFP_WAIT as was done historically now can trigger false positives. Some exceptions like dm-crypt.c exist where the code intent is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to flag manipulations. o Callers that built their own GFP flags instead of starting with GFP_KERNEL and friends now also need to specify __GFP_KSWAPD_RECLAIM. The first key hazard to watch out for is callers that removed __GFP_WAIT and was depending on access to atomic reserves for inconspicuous reasons. In some cases it may be appropriate for them to use __GFP_HIGH. The second key hazard is callers that assembled their own combination of GFP flags instead of starting with something like GFP_KERNEL. They may now wish to specify __GFP_KSWAPD_RECLAIM. It's almost certainly harmless if it's missed in most cases as other activity will wake kswapd. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
289 lines
7.1 KiB
C
289 lines
7.1 KiB
C
#include <linux/dma-mapping.h>
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#include <linux/dma-debug.h>
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#include <linux/dmar.h>
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#include <linux/export.h>
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#include <linux/bootmem.h>
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#include <linux/gfp.h>
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#include <linux/pci.h>
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#include <linux/kmemleak.h>
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#include <asm/proto.h>
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#include <asm/dma.h>
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#include <asm/iommu.h>
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#include <asm/gart.h>
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#include <asm/calgary.h>
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#include <asm/x86_init.h>
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#include <asm/iommu_table.h>
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static int forbid_dac __read_mostly;
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struct dma_map_ops *dma_ops = &nommu_dma_ops;
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EXPORT_SYMBOL(dma_ops);
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static int iommu_sac_force __read_mostly;
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#ifdef CONFIG_IOMMU_DEBUG
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int panic_on_overflow __read_mostly = 1;
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int force_iommu __read_mostly = 1;
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#else
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int panic_on_overflow __read_mostly = 0;
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int force_iommu __read_mostly = 0;
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#endif
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int iommu_merge __read_mostly = 0;
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int no_iommu __read_mostly;
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/* Set this to 1 if there is a HW IOMMU in the system */
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int iommu_detected __read_mostly = 0;
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/*
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* This variable becomes 1 if iommu=pt is passed on the kernel command line.
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* If this variable is 1, IOMMU implementations do no DMA translation for
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* devices and allow every device to access to whole physical memory. This is
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* useful if a user wants to use an IOMMU only for KVM device assignment to
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* guests and not for driver dma translation.
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*/
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int iommu_pass_through __read_mostly;
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extern struct iommu_table_entry __iommu_table[], __iommu_table_end[];
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/* Dummy device used for NULL arguments (normally ISA). */
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struct device x86_dma_fallback_dev = {
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.init_name = "fallback device",
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.coherent_dma_mask = ISA_DMA_BIT_MASK,
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.dma_mask = &x86_dma_fallback_dev.coherent_dma_mask,
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};
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EXPORT_SYMBOL(x86_dma_fallback_dev);
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/* Number of entries preallocated for DMA-API debugging */
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#define PREALLOC_DMA_DEBUG_ENTRIES 65536
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void __init pci_iommu_alloc(void)
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{
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struct iommu_table_entry *p;
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sort_iommu_table(__iommu_table, __iommu_table_end);
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check_iommu_entries(__iommu_table, __iommu_table_end);
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for (p = __iommu_table; p < __iommu_table_end; p++) {
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if (p && p->detect && p->detect() > 0) {
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p->flags |= IOMMU_DETECTED;
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if (p->early_init)
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p->early_init();
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if (p->flags & IOMMU_FINISH_IF_DETECTED)
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break;
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}
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}
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}
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void *dma_generic_alloc_coherent(struct device *dev, size_t size,
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dma_addr_t *dma_addr, gfp_t flag,
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struct dma_attrs *attrs)
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{
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unsigned long dma_mask;
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struct page *page;
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unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
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dma_addr_t addr;
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dma_mask = dma_alloc_coherent_mask(dev, flag);
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flag &= ~__GFP_ZERO;
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again:
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page = NULL;
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/* CMA can be used only in the context which permits sleeping */
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if (gfpflags_allow_blocking(flag)) {
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page = dma_alloc_from_contiguous(dev, count, get_order(size));
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if (page && page_to_phys(page) + size > dma_mask) {
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dma_release_from_contiguous(dev, page, count);
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page = NULL;
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}
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}
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/* fallback */
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if (!page)
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page = alloc_pages_node(dev_to_node(dev), flag, get_order(size));
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if (!page)
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return NULL;
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addr = page_to_phys(page);
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if (addr + size > dma_mask) {
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__free_pages(page, get_order(size));
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if (dma_mask < DMA_BIT_MASK(32) && !(flag & GFP_DMA)) {
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flag = (flag & ~GFP_DMA32) | GFP_DMA;
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goto again;
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}
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return NULL;
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}
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memset(page_address(page), 0, size);
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*dma_addr = addr;
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return page_address(page);
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}
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void dma_generic_free_coherent(struct device *dev, size_t size, void *vaddr,
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dma_addr_t dma_addr, struct dma_attrs *attrs)
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{
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unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
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struct page *page = virt_to_page(vaddr);
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if (!dma_release_from_contiguous(dev, page, count))
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free_pages((unsigned long)vaddr, get_order(size));
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}
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bool arch_dma_alloc_attrs(struct device **dev, gfp_t *gfp)
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{
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if (!*dev)
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*dev = &x86_dma_fallback_dev;
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*gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
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*gfp = dma_alloc_coherent_gfp_flags(*dev, *gfp);
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if (!is_device_dma_capable(*dev))
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return false;
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return true;
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}
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EXPORT_SYMBOL(arch_dma_alloc_attrs);
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/*
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* See <Documentation/x86/x86_64/boot-options.txt> for the iommu kernel
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* parameter documentation.
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*/
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static __init int iommu_setup(char *p)
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{
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iommu_merge = 1;
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if (!p)
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return -EINVAL;
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while (*p) {
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if (!strncmp(p, "off", 3))
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no_iommu = 1;
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/* gart_parse_options has more force support */
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if (!strncmp(p, "force", 5))
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force_iommu = 1;
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if (!strncmp(p, "noforce", 7)) {
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iommu_merge = 0;
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force_iommu = 0;
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}
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if (!strncmp(p, "biomerge", 8)) {
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iommu_merge = 1;
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force_iommu = 1;
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}
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if (!strncmp(p, "panic", 5))
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panic_on_overflow = 1;
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if (!strncmp(p, "nopanic", 7))
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panic_on_overflow = 0;
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if (!strncmp(p, "merge", 5)) {
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iommu_merge = 1;
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force_iommu = 1;
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}
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if (!strncmp(p, "nomerge", 7))
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iommu_merge = 0;
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if (!strncmp(p, "forcesac", 8))
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iommu_sac_force = 1;
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if (!strncmp(p, "allowdac", 8))
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forbid_dac = 0;
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if (!strncmp(p, "nodac", 5))
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forbid_dac = 1;
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if (!strncmp(p, "usedac", 6)) {
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forbid_dac = -1;
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return 1;
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}
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#ifdef CONFIG_SWIOTLB
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if (!strncmp(p, "soft", 4))
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swiotlb = 1;
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#endif
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if (!strncmp(p, "pt", 2))
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iommu_pass_through = 1;
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gart_parse_options(p);
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#ifdef CONFIG_CALGARY_IOMMU
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if (!strncmp(p, "calgary", 7))
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use_calgary = 1;
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#endif /* CONFIG_CALGARY_IOMMU */
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p += strcspn(p, ",");
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if (*p == ',')
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++p;
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}
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return 0;
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}
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early_param("iommu", iommu_setup);
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int dma_supported(struct device *dev, u64 mask)
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{
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struct dma_map_ops *ops = get_dma_ops(dev);
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#ifdef CONFIG_PCI
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if (mask > 0xffffffff && forbid_dac > 0) {
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dev_info(dev, "PCI: Disallowing DAC for device\n");
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return 0;
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}
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#endif
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if (ops->dma_supported)
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return ops->dma_supported(dev, mask);
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/* Copied from i386. Doesn't make much sense, because it will
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only work for pci_alloc_coherent.
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The caller just has to use GFP_DMA in this case. */
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if (mask < DMA_BIT_MASK(24))
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return 0;
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/* Tell the device to use SAC when IOMMU force is on. This
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allows the driver to use cheaper accesses in some cases.
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Problem with this is that if we overflow the IOMMU area and
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return DAC as fallback address the device may not handle it
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correctly.
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As a special case some controllers have a 39bit address
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mode that is as efficient as 32bit (aic79xx). Don't force
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SAC for these. Assume all masks <= 40 bits are of this
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type. Normally this doesn't make any difference, but gives
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more gentle handling of IOMMU overflow. */
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if (iommu_sac_force && (mask >= DMA_BIT_MASK(40))) {
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dev_info(dev, "Force SAC with mask %Lx\n", mask);
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return 0;
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}
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return 1;
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}
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EXPORT_SYMBOL(dma_supported);
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static int __init pci_iommu_init(void)
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{
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struct iommu_table_entry *p;
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dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
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#ifdef CONFIG_PCI
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dma_debug_add_bus(&pci_bus_type);
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#endif
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x86_init.iommu.iommu_init();
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for (p = __iommu_table; p < __iommu_table_end; p++) {
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if (p && (p->flags & IOMMU_DETECTED) && p->late_init)
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p->late_init();
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}
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return 0;
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}
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/* Must execute after PCI subsystem */
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rootfs_initcall(pci_iommu_init);
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#ifdef CONFIG_PCI
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/* Many VIA bridges seem to corrupt data for DAC. Disable it here */
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static void via_no_dac(struct pci_dev *dev)
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{
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if (forbid_dac == 0) {
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dev_info(&dev->dev, "disabling DAC on VIA PCI bridge\n");
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forbid_dac = 1;
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}
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}
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DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID,
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PCI_CLASS_BRIDGE_PCI, 8, via_no_dac);
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#endif
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