Messages in this thread | | | Date | Sun, 28 Nov 2021 20:12:36 -0500 | From | Sasha Levin <> | Subject | Re: [PATCH AUTOSEL 5.15 7/7] virtio-mem: support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE |
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On Fri, Nov 26, 2021 at 09:51:23AM +0100, David Hildenbrand wrote: >On 26.11.21 03:30, Sasha Levin wrote: >> From: David Hildenbrand <david@redhat.com> >> >> [ Upstream commit 61082ad6a6e1f999eef7e7e90046486c87933b1e ] >> >> The initial virtio-mem spec states that while unplugged memory should not >> be read, the device still has to allow for reading unplugged memory inside >> the usable region. The primary motivation for this default handling was >> to simplify bringup of virtio-mem, because there were corner cases where >> Linux might have accidentially read unplugged memory inside added Linux >> memory blocks. >> >> In the meantime, we: >> 1. Removed /dev/kmem in commit bbcd53c96071 ("drivers/char: remove >> /dev/kmem for good") >> 2. Disallowed access to virtio-mem device memory via /dev/mem in >> commit 2128f4e21aa2 ("virtio-mem: disallow mapping virtio-mem memory via >> /dev/mem") >> 3. Sanitized access to virtio-mem device memory via /proc/kcore in >> commit 0daa322b8ff9 ("fs/proc/kcore: don't read offline sections, >> logically offline pages and hwpoisoned pages") >> 4. Sanitized access to virtio-mem device memory via /proc/vmcore in >> commit ce2814622e84 ("virtio-mem: kdump mode to sanitize /proc/vmcore >> access") >> >> "Accidential" access to unplugged memory is no longer possible; we can >> support the new VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE feature that will be >> required by some hypervisors implementing virtio-mem in the near future. >> >> Acked-by: Michael S. Tsirkin <mst@redhat.com> >> Cc: "Michael S. Tsirkin" <mst@redhat.com> >> Cc: Jason Wang <jasowang@redhat.com> >> Cc: Marek Kedzierski <mkedzier@redhat.com> >> Cc: Hui Zhu <teawater@gmail.com> >> Cc: Sebastien Boeuf <sebastien.boeuf@intel.com> >> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com> >> Cc: Wei Yang <richard.weiyang@linux.alibaba.com> >> Signed-off-by: David Hildenbrand <david@redhat.com> >> Signed-off-by: Sasha Levin <sashal@kernel.org> >> --- >> drivers/virtio/virtio_mem.c | 1 + >> include/uapi/linux/virtio_mem.h | 9 ++++++--- >> 2 files changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c >> index bef8ad6bf4661..78dfdc9c98a1c 100644 >> --- a/drivers/virtio/virtio_mem.c >> +++ b/drivers/virtio/virtio_mem.c >> @@ -2758,6 +2758,7 @@ static unsigned int virtio_mem_features[] = { >> #if defined(CONFIG_NUMA) && defined(CONFIG_ACPI_NUMA) >> VIRTIO_MEM_F_ACPI_PXM, >> #endif >> + VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE, >> }; >> >> static const struct virtio_device_id virtio_mem_id_table[] = { >> diff --git a/include/uapi/linux/virtio_mem.h b/include/uapi/linux/virtio_mem.h >> index 70e01c687d5eb..e9122f1d0e0cb 100644 >> --- a/include/uapi/linux/virtio_mem.h >> +++ b/include/uapi/linux/virtio_mem.h >> @@ -68,9 +68,10 @@ >> * explicitly triggered (VIRTIO_MEM_REQ_UNPLUG). >> * >> * There are no guarantees what will happen if unplugged memory is >> - * read/written. Such memory should, in general, not be touched. E.g., >> - * even writing might succeed, but the values will simply be discarded at >> - * random points in time. >> + * read/written. In general, unplugged memory should not be touched, because >> + * the resulting action is undefined. There is one exception: without >> + * VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE, unplugged memory inside the usable >> + * region can be read, to simplify creation of memory dumps. >> * >> * It can happen that the device cannot process a request, because it is >> * busy. The device driver has to retry later. >> @@ -87,6 +88,8 @@ >> >> /* node_id is an ACPI PXM and is valid */ >> #define VIRTIO_MEM_F_ACPI_PXM 0 >> +/* unplugged memory must not be accessed */ >> +#define VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE 1 >> >> >> /* --- virtio-mem: guest -> host requests --- */ >> > >As 2. and 4. are part of v5.16-rc1 but not v5.15-stable > >Nacked-by: David Hildenbrand <david@redhat.com>
I'll drop them, thanks!
-- Thanks, Sasha
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