From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration Manually perform cache maintenance on the source VM during intra-host migration to ensure no stale data is left in CPU caches after the VM is destroyed. Because the source VM is "converted" to a non-SEV VM, KVM's memory reclaim flows won't trigger cache maintenance, e.g. when all guest memory is reclaimed in response to detaching from the mmu_notifier. Note, relying on the destination VM to do cache maintenance isn't an option as KVM doesn't require identical guest memory configurations, i.e. the source VM may have access to memory that the destination VM does not. Enforcing equivalent memory configurations is infeasible, as it would require a *deep* comparison of memslots, e.g. to verify that not only are the memslot identical, but what the memslots point at is also identical. Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration") Cc: stable@vger.kernel.org Reported-by: Stefan Teodorescu Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- Documentation/ABI/testing/sysfs-class-rnbd-client | 133 ++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-rnbd-client (limited to 'Documentation/ABI/testing/sysfs-class-rnbd-client') diff --git a/Documentation/ABI/testing/sysfs-class-rnbd-client b/Documentation/ABI/testing/sysfs-class-rnbd-client new file mode 100644 index 000000000..0b5997ab3 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-rnbd-client @@ -0,0 +1,133 @@ +What: /sys/class/rnbd-client +Date: Feb 2020 +KernelVersion: 5.7 +Contact: Jack Wang Danil Kipnis +Description: Provide information about RNBD-client. + All sysfs files that are not read-only provide the usage information on read: + + Example:: + + # cat /sys/class/rnbd-client/ctl/map_device + + > Usage: echo "sessname= path=<[srcaddr,]dstaddr> + > [path=<[srcaddr,]dstaddr>] device_path= + > [access_mode=] > map_device + > + > addr ::= [ ip: | ip: | gid: ] + +What: /sys/class/rnbd-client/ctl/map_device +Date: Feb 2020 +KernelVersion: 5.7 +Contact: Jack Wang Danil Kipnis +Description: Expected format is the following:: + + sessname= + path=<[srcaddr,]dstaddr> [path=<[srcaddr,]dstaddr> ...] + device_path= + [access_mode=] + + Where: + + sessname: + accepts a string not bigger than 256 chars, which identifies + a given session on the client and on the server. + I.e. "clt_hostname-srv_hostname" could be a natural choice. + + path: + describes a connection between the client and the server by + specifying destination and, when required, the source address. + The addresses are to be provided in the following format:: + + ip: + ip: + gid: + + for example:: + + path=ip:10.0.0.66 + + The single addr is treated as the destination. + The connection will be established to this server from any client IP address. + + :: + + path=ip:10.0.0.66,ip:10.0.1.66 + + First addr is the source address and the second is the destination. + + If multiple "path=" options are specified multiple connection + will be established and data will be sent according to + the selected multipath policy (see RTRS mp_policy sysfs entry description). + + device_path: + Path to the block device on the server side. Path is specified + relative to the directory on server side configured in the + 'dev_search_path' module parameter of the rnbd_server. + The rnbd_server prepends the received from client + with and tries to open the + / block device. On success, + a /dev/rnbd device file, a /sys/block/rnbd/ + directory and an entry in /sys/class/rnbd-client/ctl/devices + will be created. + + If 'dev_search_path' contains '%SESSNAME%', then each session can + have different devices namespace, e.g. server was configured with + the following parameter "dev_search_path=/run/rnbd-devs/%SESSNAME%", + client has this string "sessname=blya device_path=sda", then server + will try to open: /run/rnbd-devs/blya/sda. + + access_mode: + the access_mode parameter specifies if the device is to be + mapped as "ro" read-only or "rw" read-write. The server allows + a device to be exported in rw mode only once. The "migration" + access mode has to be specified if a second mapping in read-write + mode is desired. + + By default "rw" is used. + + nr_poll_queues + specifies the number of poll-mode queues. If the IO has HIPRI flag, + the block-layer will send the IO via the poll-mode queue. + For fast network and device the polling is faster than interrupt-base + IO handling because it saves time for context switching, switching to + another process, handling the interrupt and switching back to the + issuing process. + + Set -1 if you want to set it as the number of CPUs + By default rnbd client creates only irq-mode queues. + + NOTICE: MUST make a unique session for a device using the poll-mode queues. + + Exit Codes: + + If the device is already mapped it will fail with EEXIST. If the input + has an invalid format it will return EINVAL. If the device path cannot + be found on the server, it will fail with ENOENT. + + Finding device file after mapping + --------------------------------- + + After mapping, the device file can be found by: + o The symlink /sys/class/rnbd-client/ctl/devices/@ + points to /sys/block/. The last part of the symlink destination + is the same as the device name. By extracting the last part of the + path the path to the device /dev/ can be build. + + * /dev/block/$(cat /sys/class/rnbd-client/ctl/devices/@/dev) + + How to find the of the device is described on the next + section. + +What: /sys/class/rnbd-client/ctl/devices/ +Date: Feb 2020 +KernelVersion: 5.7 +Contact: Jack Wang Danil Kipnis +Description: For each device mapped on the client a new symbolic link is created as + /sys/class/rnbd-client/ctl/devices/@, which points + to the block device created by rnbd (/sys/block/rnbd/). + The of each device is created as follows: + + - If the 'device_path' provided during mapping contains slashes ("/"), + they are replaced by exclamation mark ("!") and used as as the + . Otherwise, the will be the same as the + "device_path" provided. -- cgit v1.3.1