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[79.181.55.232]) by smtp.gmail.com with ESMTPSA id u4sm3363234wmb.48.2020.06.11.03.07.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jun 2020 03:07:57 -0700 (PDT) Date: Thu, 11 Jun 2020 06:07:54 -0400 From: "Michael S. Tsirkin" To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Jason Wang , Pankaj Gupta , teawater Subject: Re: [PATCH v1] virtio-mem: add memory via add_memory_driver_managed() Message-ID: <20200611060249-mutt-send-email-mst@kernel.org> References: <20200611093518.5737-1-david@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200611093518.5737-1-david@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Queue-Id: A6A02169CE4 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: virtio-mem: add memory via add_memory_driver_managed() On Thu, Jun 11, 2020 at 11:35:18AM +0200, David Hildenbrand wrote: > Virtio-mem managed memory is always detected and added by the virtio-mem > driver, never using something like the firmware-provided memory map. > This is the case after an ordinary system reboot, and has to be guaranteed > after kexec. Especially, virtio-mem added memory resources can contain > inaccessible parts ("unblocked memory blocks"), blindly forwarding them > to a kexec kernel is dangerous, as unplugged memory will get accessed > (esp. written). > > Let's use the new way of adding special driver-managed memory introduced > in commit 75ac4c58bc0d ("mm/memory_hotplug: introduce > add_memory_driver_managed()"). > > This will result in no entries in /sys/firmware/memmap ("raw firmware- > provided memory map"), the memory resource will be flagged > IORESOURCE_MEM_DRIVER_MANAGED (esp., kexec_file_load() will not place > kexec images on this memory), and it is exposed as "System RAM > (virtio_mem)" in /proc/iomem, so esp. kexec-tools can properly handle it. > > Example /proc/iomem before this change: > [...] > 140000000-333ffffff : virtio0 > 140000000-147ffffff : System RAM > 334000000-533ffffff : virtio1 > 338000000-33fffffff : System RAM > 340000000-347ffffff : System RAM > 348000000-34fffffff : System RAM > [...] > > Example /proc/iomem after this change: > [...] > 140000000-333ffffff : virtio0 > 140000000-147ffffff : System RAM (virtio_mem) > 334000000-533ffffff : virtio1 > 338000000-33fffffff : System RAM (virtio_mem) > 340000000-347ffffff : System RAM (virtio_mem) > 348000000-34fffffff : System RAM (virtio_mem) > [...] > > Cc: "Michael S. Tsirkin" > Cc: Pankaj Gupta > Cc: teawater > Signed-off-by: David Hildenbrand > --- > > Based on latest Linus' tree (and not a tag) because > - virtio-mem has just been merged via the vhost tree > - add_memory_driver_managed() has been merged a week ago via the -mm tree > > I'd like to have this patch in 5.8, with the initial merge of virtio-mem > if possible (so the user space representation of virtio-mem added memory > resources won't change anymore). So my plan is to rebase on top of -rc1 and merge this for rc2 then. I don't like rebase on top of tip as the results are sometimes kind of random. And let's add a Fixes: tag as well, this way people will remember to pick this. Makes sense? > --- > drivers/virtio/virtio_mem.c | 25 ++++++++++++++++++++++--- > 1 file changed, 22 insertions(+), 3 deletions(-) > > diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c > index 50c689f250450..d2eab3558a9e1 100644 > --- a/drivers/virtio/virtio_mem.c > +++ b/drivers/virtio/virtio_mem.c > @@ -101,6 +101,11 @@ struct virtio_mem { > > /* The parent resource for all memory added via this device. */ > struct resource *parent_resource; > + /* > + * Copy of "System RAM (virtio_mem)" to be used for > + * add_memory_driver_managed(). > + */ > + const char *resource_name; > > /* Summary of all memory block states. */ > unsigned long nb_mb_state[VIRTIO_MEM_MB_STATE_COUNT]; > @@ -414,8 +419,20 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id) > if (nid == NUMA_NO_NODE) > nid = memory_add_physaddr_to_nid(addr); > > + /* > + * When force-unloading the driver and we still have memory added to > + * Linux, the resource name has to stay. > + */ > + if (!vm->resource_name) { > + vm->resource_name = kstrdup_const("System RAM (virtio_mem)", > + GFP_KERNEL); > + if (!vm->resource_name) > + return -ENOMEM; > + } > + > dev_dbg(&vm->vdev->dev, "adding memory block: %lu\n", mb_id); > - return add_memory(nid, addr, memory_block_size_bytes()); > + return add_memory_driver_managed(nid, addr, memory_block_size_bytes(), > + vm->resource_name); > } > > /* > @@ -1890,10 +1907,12 @@ static void virtio_mem_remove(struct virtio_device *vdev) > vm->nb_mb_state[VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL] || > vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE] || > vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE_PARTIAL] || > - vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE_MOVABLE]) > + vm->nb_mb_state[VIRTIO_MEM_MB_STATE_ONLINE_MOVABLE]) { > dev_warn(&vdev->dev, "device still has system memory added\n"); > - else > + } else { > virtio_mem_delete_resource(vm); > + kfree_const(vm->resource_name); > + } > > /* remove all tracking data - no locking needed */ > vfree(vm->mb_state); > -- > 2.26.2