linux-kernel - [PATCH 05/16] mm/hmm/test: remove redundant page table invalidate

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Message-ID: <20200619215649.32297-6-rcampbell@nvidia.com>
Date:   Fri, 19 Jun 2020 14:56:38 -0700
From:   Ralph Campbell <rcampbell@...dia.com>
To:     <nouveau@...ts.freedesktop.org>, <linux-rdma@...r.kernel.org>,
        <linux-mm@...ck.org>, <linux-kselftest@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Jerome Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@....de>,
        Jason Gunthorpe <jgg@...lanox.com>,
        "Ben Skeggs" <bskeggs@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>,
        Ralph Campbell <rcampbell@...dia.com>
Subject: [PATCH 05/16] mm/hmm/test: remove redundant page table invalidate

When migrating pages to or from device private memory, the device's
page tables will be invalidated as part of migrate_vma_setup() locking
and isolating the pages. The HMM self test driver doesn't need to
invalidate the page table a second time after migrating pages to system
memory so remove that bit of extra code.

Signed-off-by: Ralph Campbell <rcampbell@...dia.com>
---
 lib/test_hmm.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 28528285942c..f7c2b51a7a9d 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -1018,15 +1018,6 @@ static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
 	return 0;
 }
 
-static void dmirror_devmem_fault_finalize_and_map(struct migrate_vma *args,
-						  struct dmirror *dmirror)
-{
-	/* Invalidate the device's page table mapping. */
-	mutex_lock(&dmirror->mutex);
-	dmirror_do_update(dmirror, args->start, args->end);
-	mutex_unlock(&dmirror->mutex);
-}
-
 static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf)
 {
 	struct migrate_vma args;
@@ -1059,7 +1050,10 @@ static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf)
 	if (ret)
 		return ret;
 	migrate_vma_pages(&args);
-	dmirror_devmem_fault_finalize_and_map(&args, dmirror);
+	/*
+	 * No device finalize step is needed since migrate_vma_setup() will
+	 * have already invalidated the device page table.
+	 */
 	migrate_vma_finalize(&args);
 	return 0;
 }
-- 
2.20.1