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authorBalbir Singh <bsingharora@gmail.com>2016-09-06 16:27:31 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2016-09-29 15:14:44 +1000
commit2e5bbb5461f138cac631fe21b4ad956feabfba22 (patch)
treeeb89de095b80a8f419022bb05ec40cf16a6cf3a7
parent360aebd85a4c946764f6301d68de2a817fad5159 (diff)
KVM: PPC: Book3S HV: Migrate pinned pages out of CMA
When PCI Device pass-through is enabled via VFIO, KVM-PPC will pin pages using get_user_pages_fast(). One of the downsides of the pinning is that the page could be in CMA region. The CMA region is used for other allocations like the hash page table. Ideally we want the pinned pages to be from non CMA region. This patch (currently only for KVM PPC with VFIO) forcefully migrates the pages out (huge pages are omitted for the moment). There are more efficient ways of doing this, but that might be elaborate and might impact a larger audience beyond just the kvm ppc implementation. The magic is in new_iommu_non_cma_page() which allocates the new page from a non CMA region. I've tested the patches lightly at my end. The full solution requires migration of THP pages in the CMA region. That work will be done incrementally on top of this. Signed-off-by: Balbir Singh <bsingharora@gmail.com> Acked-by: Alexey Kardashevskiy <aik@ozlabs.ru> [mpe: Merged via powerpc tree as that's where the changes are] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
-rw-r--r--arch/powerpc/include/asm/mmu_context.h1
-rw-r--r--arch/powerpc/mm/mmu_context_iommu.c81
2 files changed, 78 insertions, 4 deletions
diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 9d2cd0c36ec2..475d1be39191 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -18,6 +18,7 @@ extern void destroy_context(struct mm_struct *mm);
#ifdef CONFIG_SPAPR_TCE_IOMMU
struct mm_iommu_table_group_mem_t;
+extern int isolate_lru_page(struct page *page); /* from internal.h */
extern bool mm_iommu_preregistered(void);
extern long mm_iommu_get(unsigned long ua, unsigned long entries,
struct mm_iommu_table_group_mem_t **pmem);
diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
index da6a2168ae9e..e0f1c33601dd 100644
--- a/arch/powerpc/mm/mmu_context_iommu.c
+++ b/arch/powerpc/mm/mmu_context_iommu.c
@@ -15,6 +15,9 @@
#include <linux/rculist.h>
#include <linux/vmalloc.h>
#include <linux/mutex.h>
+#include <linux/migrate.h>
+#include <linux/hugetlb.h>
+#include <linux/swap.h>
#include <asm/mmu_context.h>
static DEFINE_MUTEX(mem_list_mutex);
@@ -72,6 +75,55 @@ bool mm_iommu_preregistered(void)
}
EXPORT_SYMBOL_GPL(mm_iommu_preregistered);
+/*
+ * Taken from alloc_migrate_target with changes to remove CMA allocations
+ */
+struct page *new_iommu_non_cma_page(struct page *page, unsigned long private,
+ int **resultp)
+{
+ gfp_t gfp_mask = GFP_USER;
+ struct page *new_page;
+
+ if (PageHuge(page) || PageTransHuge(page) || PageCompound(page))
+ return NULL;
+
+ if (PageHighMem(page))
+ gfp_mask |= __GFP_HIGHMEM;
+
+ /*
+ * We don't want the allocation to force an OOM if possibe
+ */
+ new_page = alloc_page(gfp_mask | __GFP_NORETRY | __GFP_NOWARN);
+ return new_page;
+}
+
+static int mm_iommu_move_page_from_cma(struct page *page)
+{
+ int ret = 0;
+ LIST_HEAD(cma_migrate_pages);
+
+ /* Ignore huge pages for now */
+ if (PageHuge(page) || PageTransHuge(page) || PageCompound(page))
+ return -EBUSY;
+
+ lru_add_drain();
+ ret = isolate_lru_page(page);
+ if (ret)
+ return ret;
+
+ list_add(&page->lru, &cma_migrate_pages);
+ put_page(page); /* Drop the gup reference */
+
+ ret = migrate_pages(&cma_migrate_pages, new_iommu_non_cma_page,
+ NULL, 0, MIGRATE_SYNC, MR_CMA);
+ if (ret) {
+ if (!list_empty(&cma_migrate_pages))
+ putback_movable_pages(&cma_migrate_pages);
+ }
+
+ return 0;
+}
+
long mm_iommu_get(unsigned long ua, unsigned long entries,
struct mm_iommu_table_group_mem_t **pmem)
{
@@ -124,15 +176,36 @@ long mm_iommu_get(unsigned long ua, unsigned long entries,
for (i = 0; i < entries; ++i) {
if (1 != get_user_pages_fast(ua + (i << PAGE_SHIFT),
1/* pages */, 1/* iswrite */, &page)) {
+ ret = -EFAULT;
for (j = 0; j < i; ++j)
- put_page(pfn_to_page(
- mem->hpas[j] >> PAGE_SHIFT));
+ put_page(pfn_to_page(mem->hpas[j] >>
+ PAGE_SHIFT));
vfree(mem->hpas);
kfree(mem);
- ret = -EFAULT;
goto unlock_exit;
}
-
+ /*
+ * If we get a page from the CMA zone, since we are going to
+ * be pinning these entries, we might as well move them out
+ * of the CMA zone if possible. NOTE: faulting in + migration
+ * can be expensive. Batching can be considered later
+ */
+ if (get_pageblock_migratetype(page) == MIGRATE_CMA) {
+ if (mm_iommu_move_page_from_cma(page))
+ goto populate;
+ if (1 != get_user_pages_fast(ua + (i << PAGE_SHIFT),
+ 1/* pages */, 1/* iswrite */,
+ &page)) {
+ ret = -EFAULT;
+ for (j = 0; j < i; ++j)
+ put_page(pfn_to_page(mem->hpas[j] >>
+ PAGE_SHIFT));
+ vfree(mem->hpas);
+ kfree(mem);
+ goto unlock_exit;
+ }
+ }
+populate:
mem->hpas[i] = page_to_pfn(page) << PAGE_SHIFT;
}