From: David Hildenbrand <david@redhat.com> To: linux-kernel@vger.kernel.org Cc: David Hildenbrand <david@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, "Michael S. Tsirkin" <mst@redhat.com>, Jason Wang <jasowang@redhat.com>, Alexey Dobriyan <adobriyan@gmail.com>, Mike Rapoport <rppt@kernel.org>, "Matthew Wilcox (Oracle)" <willy@infradead.org>, Oscar Salvador <osalvador@suse.de>, Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>, Alex Shi <alex.shi@linux.alibaba.com>, Steven Price <steven.price@arm.com>, Mike Kravetz <mike.kravetz@oracle.com>, Aili Yao <yaoaili@kingsoft.com>, Jiri Bohac <jbohac@suse.cz>, "K. Y. Srinivasan" <kys@microsoft.com>, Haiyang Zhang <haiyangz@microsoft.com>, Stephen Hemminger <sthemmin@microsoft.com>, Wei Liu <wei.liu@kernel.org>, Naoya Horiguchi <naoya.horiguchi@nec.com>, linux-hyperv@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 5/6] virtio-mem: use page_offline_(start|end) when setting PageOffline() Date: Fri, 14 May 2021 19:22:46 +0200 [thread overview] Message-ID: <20210514172247.176750-6-david@redhat.com> (raw) In-Reply-To: <20210514172247.176750-1-david@redhat.com> Let's properly use page_offline_(start|end) to synchronize setting PageOffline(), so we won't have valid page access to unplugged memory regions from /proc/kcore. Existing balloon implementations usually allow reading inflated memory; doing so might result in unnecessary overhead in the hypervisor, which is currently the case with virtio-mem. For future virtio-mem use cases, it will be different when using shmem, huge pages, !anonymous private mappings, ... as backing storage for a VM. virtio-mem unplugged memory must no longer be accessed and access might result in undefined behavior. There will be a virtio spec extension to document this change, including a new feature flag indicating the changed behavior. We really don't want to race against PFN walkers reading random page content. Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- drivers/virtio/virtio_mem.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 10ec60d81e84..dc2a2e2b2ff8 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -1065,6 +1065,7 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb, static void virtio_mem_set_fake_offline(unsigned long pfn, unsigned long nr_pages, bool onlined) { + page_offline_begin(); for (; nr_pages--; pfn++) { struct page *page = pfn_to_page(pfn); @@ -1075,6 +1076,7 @@ static void virtio_mem_set_fake_offline(unsigned long pfn, ClearPageReserved(page); } } + page_offline_end(); } /* -- 2.31.1
WARNING: multiple messages have this Message-ID (diff)
From: David Hildenbrand <david@redhat.com> To: linux-kernel@vger.kernel.org Cc: Aili Yao <yaoaili@kingsoft.com>, Michal Hocko <mhocko@suse.com>, "Michael S. Tsirkin" <mst@redhat.com>, linux-hyperv@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, Wei Liu <wei.liu@kernel.org>, Alex Shi <alex.shi@linux.alibaba.com>, Stephen Hemminger <sthemmin@microsoft.com>, "Matthew Wilcox \(Oracle\)" <willy@infradead.org>, Steven Price <steven.price@arm.com>, Alexey Dobriyan <adobriyan@gmail.com>, Jiri Bohac <jbohac@suse.cz>, Haiyang Zhang <haiyangz@microsoft.com>, Oscar Salvador <osalvador@suse.de>, Naoya Horiguchi <naoya.horiguchi@nec.com>, linux-fsdevel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, Roman Gushchin <guro@fb.com>, Mike Rapoport <rppt@kernel.org>, Mike Kravetz <mike.kravetz@oracle.com> Subject: [PATCH v2 5/6] virtio-mem: use page_offline_(start|end) when setting PageOffline() Date: Fri, 14 May 2021 19:22:46 +0200 [thread overview] Message-ID: <20210514172247.176750-6-david@redhat.com> (raw) In-Reply-To: <20210514172247.176750-1-david@redhat.com> Let's properly use page_offline_(start|end) to synchronize setting PageOffline(), so we won't have valid page access to unplugged memory regions from /proc/kcore. Existing balloon implementations usually allow reading inflated memory; doing so might result in unnecessary overhead in the hypervisor, which is currently the case with virtio-mem. For future virtio-mem use cases, it will be different when using shmem, huge pages, !anonymous private mappings, ... as backing storage for a VM. virtio-mem unplugged memory must no longer be accessed and access might result in undefined behavior. There will be a virtio spec extension to document this change, including a new feature flag indicating the changed behavior. We really don't want to race against PFN walkers reading random page content. Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- drivers/virtio/virtio_mem.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 10ec60d81e84..dc2a2e2b2ff8 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -1065,6 +1065,7 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb, static void virtio_mem_set_fake_offline(unsigned long pfn, unsigned long nr_pages, bool onlined) { + page_offline_begin(); for (; nr_pages--; pfn++) { struct page *page = pfn_to_page(pfn); @@ -1075,6 +1076,7 @@ static void virtio_mem_set_fake_offline(unsigned long pfn, ClearPageReserved(page); } } + page_offline_end(); } /* -- 2.31.1 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2021-05-14 17:24 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-14 17:22 [PATCH v2 0/6] fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages David Hildenbrand 2021-05-14 17:22 ` David Hildenbrand 2021-05-14 17:22 ` [PATCH v2 1/6] fs/proc/kcore: drop KCORE_REMAP and KCORE_OTHER David Hildenbrand 2021-05-14 17:22 ` David Hildenbrand 2021-05-14 17:22 ` [PATCH v2 2/6] fs/proc/kcore: pfn_is_ram check only applies to KCORE_RAM David Hildenbrand 2021-05-14 17:22 ` David Hildenbrand 2021-05-14 17:22 ` [PATCH v2 3/6] fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages David Hildenbrand 2021-05-14 17:22 ` David Hildenbrand 2021-05-25 8:09 ` Oscar Salvador 2021-05-14 17:22 ` [PATCH v2 4/6] mm: introduce page_offline_(begin|end|freeze|thaw) to synchronize setting PageOffline() David Hildenbrand 2021-05-14 17:22 ` David Hildenbrand 2021-05-17 6:43 ` Mike Rapoport 2021-05-17 15:18 ` David Hildenbrand 2021-05-17 15:18 ` David Hildenbrand 2021-05-25 8:16 ` Oscar Salvador 2021-05-14 17:22 ` David Hildenbrand [this message] 2021-05-14 17:22 ` [PATCH v2 5/6] virtio-mem: use page_offline_(start|end) when " David Hildenbrand 2021-05-17 6:43 ` Mike Rapoport 2021-05-25 8:20 ` Oscar Salvador 2021-05-14 17:22 ` [PATCH v2 6/6] fs/proc/kcore: use page_offline_(freeze|thaw) David Hildenbrand 2021-05-14 17:22 ` David Hildenbrand 2021-05-17 6:44 ` Mike Rapoport 2021-05-25 8:21 ` Oscar Salvador
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