linux-kernel - [PATCH v1 3/3] virtio-mem: Add memory with MHP_DRIVER

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Date:   Wed, 29 Apr 2020 18:08:03 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, virtio-dev@...ts.oasis-open.org,
        virtualization@...ts.linux-foundation.org,
        linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-hyperv@...r.kernel.org,
        linux-s390@...r.kernel.org, xen-devel@...ts.xenproject.org,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        Eric Biederman <ebiederm@...ssion.com>
Subject: [PATCH v1 3/3] virtio-mem: Add memory with MHP_DRIVER_MANAGED

We don't want /sys/firmware/memmap entries and we want to indicate
our memory as "System RAM (driver managed)" in /proc/iomem. This is
especially relevant for kexec-tools, which have to be updated to
support dumping virtio-mem memory after this patch. Expected behavior in
kexec-tools:
- Don't use this memory when creating a fixed-up firmware memmap. Works
  now out of the box on x86-64.
- Don't use this memory for placing kexec segments. Works now out of the
  box on x86-64.
- Consider "System RAM (driver managed)" when creating the elfcorehdr
  for kdump. This memory has to be dumped. Needs update of kexec-tools.

With this patch on x86-64:

/proc/iomem:
	00000000-00000fff : Reserved
	00001000-0009fbff : System RAM
	[...]
	fffc0000-ffffffff : Reserved
	100000000-13fffffff : System RAM
	140000000-147ffffff : System RAM (driver managed)
	340000000-347ffffff : System RAM (driver managed)
	348000000-34fffffff : System RAM (driver managed)
	[..]
	3280000000-32ffffffff : PCI Bus 0000:00

/sys/firmware/memmap:
	0000000000000000-000000000009fc00 (System RAM)
	000000000009fc00-00000000000a0000 (Reserved)
	00000000000f0000-0000000000100000 (Reserved)
	0000000000100000-00000000bffe0000 (System RAM)
	00000000bffe0000-00000000c0000000 (Reserved)
	00000000feffc000-00000000ff000000 (Reserved)
	00000000fffc0000-0000000100000000 (Reserved)
	0000000100000000-0000000140000000 (System RAM)

Cc: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Jason Wang <jasowang@...hat.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Eric Biederman <ebiederm@...ssion.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 drivers/virtio/virtio_mem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 3101cbf9e59d..6f658d1aeac4 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -421,7 +421,8 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
 		nid = memory_add_physaddr_to_nid(addr);
 
 	dev_dbg(&vm->vdev->dev, "adding memory block: %lu\n", mb_id);
-	return add_memory(nid, addr, memory_block_size_bytes(), 0);
+	return add_memory(nid, addr, memory_block_size_bytes(),
+			  MHP_DRIVER_MANAGED);
 }
 
 /*
-- 
2.25.3