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Violators will be prosecuted for from ; Thu, 14 Jul 2016 13:11:09 +1000 Received: from d23relay07.au.ibm.com (d23relay07.au.ibm.com [9.190.26.37]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id D62783578057 for ; Thu, 14 Jul 2016 13:11:05 +1000 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay07.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u6E3B5jp15663230 for ; Thu, 14 Jul 2016 13:11:05 +1000 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u6E3B5Rn030874 for ; Thu, 14 Jul 2016 13:11:05 +1000 Subject: [v2][PATCH] KVM: PPC: Book3S HV: Migrate pinned pages out of CMA From: Balbir Singh Date: Thu, 14 Jul 2016 13:11:03 +1000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Message-Id: <57d99598-2350-9578-5f93-b551cda12d23@ozlabs.au.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org Cc: "linux-mm@kvack.org" , Benjamin Herrenschmidt , Alexey Kardashevskiy , Paul Mackerras , Michael Ellerman 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, but there might be bugs For example if after lru_add_drain(), the page is not isolated is this a BUG? Previous discussion was at http://permalink.gmane.org/gmane.linux.kernel.mm/136738 Cc: Benjamin Herrenschmidt Cc: Michael Ellerman Cc: Paul Mackerras Cc: Alexey Kardashevskiy Signed-off-by: Balbir Singh --- arch/powerpc/include/asm/mmu_context.h | 1 + arch/powerpc/mm/mmu_context_iommu.c | 80 ++++++++++++++++++++++++++++++++-- 2 files changed, 77 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h index 9d2cd0c..475d1be 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 da6a216..c18f742 100644 --- a/arch/powerpc/mm/mmu_context_iommu.c +++ b/arch/powerpc/mm/mmu_context_iommu.c @@ -15,6 +15,9 @@ #include #include #include +#include +#include +#include #include static DEFINE_MUTEX(mem_list_mutex); @@ -72,6 +75,54 @@ 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; + 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) + get_page(page); /* Potential BUG? */ + + 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 +175,36 @@ 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; } -- 2.5.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org