From: Ralph Campbell <rcampbell@nvidia.com>
To: <linux-mm@kvack.org>
Cc: linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org,
dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Christoph Hellwig" <hch@lst.de>,
"Ralph Campbell" <rcampbell@nvidia.com>
Subject: [PATCH 2/4] mm/hmm: allow snapshot of the special zero page
Date: Wed, 11 Sep 2019 15:28:27 -0700 [thread overview]
Message-ID: <20190911222829.28874-3-rcampbell@nvidia.com> (raw)
In-Reply-To: <20190911222829.28874-1-rcampbell@nvidia.com>
Allow hmm_range_fault() to return success (0) when the CPU pagetable
entry points to the special shared zero page.
The caller can then handle the zero page by possibly clearing device
private memory instead of DMAing a zero page.
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
---
mm/hmm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/hmm.c b/mm/hmm.c
index 06041d4399ff..7217912bef13 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -532,7 +532,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
return -EBUSY;
} else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) {
*pfn = range->values[HMM_PFN_SPECIAL];
- return -EFAULT;
+ return is_zero_pfn(pte_pfn(pte)) ? 0 : -EFAULT;
}
*pfn = hmm_device_entry_from_pfn(range, pte_pfn(pte)) | cpu_flags;
--
2.20.1
next prev parent reply other threads:[~2019-09-11 22:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 22:28 [PATCH 0/4] HMM tests and minor fixes Ralph Campbell
2019-09-11 22:28 ` [PATCH 1/4] mm/hmm: make full use of walk_page_range() Ralph Campbell
2019-09-12 8:26 ` Christoph Hellwig
2019-09-12 17:16 ` Ralph Campbell
2019-09-11 22:28 ` Ralph Campbell [this message]
2019-09-12 8:26 ` [PATCH 2/4] mm/hmm: allow snapshot of the special zero page Christoph Hellwig
2019-09-12 17:08 ` Ralph Campbell
2019-09-11 22:28 ` [PATCH 3/4] mm/hmm: allow hmm_range_fault() of mmap(PROT_NONE) Ralph Campbell
2019-09-11 22:28 ` [PATCH 4/4] mm/hmm/test: add self tests for HMM Ralph Campbell
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