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From: Alistair Popple <alistair@popple.id.au>
To: linuxppc-dev@lists.ozlabs.org
Cc: Alistair Popple <alistair@popple.id.au>, bharata@linux.ibm.com
Subject: [PATCH] powerpc/book3s_hv_uvmem: Check for failed page migration
Date: Thu,  3 Dec 2020 16:08:12 +1100	[thread overview]
Message-ID: <20201203050812.5234-1-alistair@popple.id.au> (raw)

migrate_vma_pages() may still clear MIGRATE_PFN_MIGRATE on pages which
are not able to be migrated. Drivers may safely copy data prior to
calling migrate_vma_pages() however a remote mapping must not be
established until after migrate_vma_pages() has returned as the
migration could still fail.

UV_PAGE_IN_in both copies and maps the data page, therefore it should
only be called after checking the results of migrate_vma_pages().

Signed-off-by: Alistair Popple <alistair@popple.id.au>
---
 arch/powerpc/kvm/book3s_hv_uvmem.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 84e5a2dc8be5..08aa6a90c525 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -762,7 +762,10 @@ static int kvmppc_svm_page_in(struct vm_area_struct *vma,
 		goto out_finalize;
 	}
 
-	if (pagein) {
+	*mig.dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED;
+	migrate_vma_pages(&mig);
+
+	if ((*mig.src & MIGRATE_PFN_MIGRATE) && pagein) {
 		pfn = *mig.src >> MIGRATE_PFN_SHIFT;
 		spage = migrate_pfn_to_page(*mig.src);
 		if (spage) {
@@ -773,8 +776,6 @@ static int kvmppc_svm_page_in(struct vm_area_struct *vma,
 		}
 	}
 
-	*mig.dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED;
-	migrate_vma_pages(&mig);
 out_finalize:
 	migrate_vma_finalize(&mig);
 	return ret;
-- 
2.20.1


             reply	other threads:[~2020-12-03  5:10 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-03  5:08 Alistair Popple [this message]
2020-12-04 10:18 ` [PATCH] powerpc/book3s_hv_uvmem: Check for failed page migration Bharata B Rao
2020-12-04 16:52   ` Ram Pai
2020-12-07  0:13     ` Alistair Popple
2020-12-06 23:55   ` Alistair Popple
2020-12-08 14:20 ` Ram Pai

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