KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

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 <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-remoteproc b/Documentation/ABI/testing/sysfs-class-remoteproc
new file mode 100644
index 000000000..b2b8e2db2
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+What:		/sys/class/remoteproc/.../firmware
+Date:		October 2016
+Contact:	Matt Redfearn <matt.redfearn@mips.com>
+Description:	Remote processor firmware
+
+		Reports the name of the firmware currently loaded to the
+		remote processor.
+
+		To change the running firmware, ensure the remote processor is
+		stopped (using /sys/class/remoteproc/.../state) and write a new filename.
+
+What:		/sys/class/remoteproc/.../state
+Date:		October 2016
+Contact:	Matt Redfearn <matt.redfearn@mips.com>
+Description:	Remote processor state
+
+		Reports the state of the remote processor, which will be one of:
+
+		- "offline"
+		- "suspended"
+		- "running"
+		- "crashed"
+		- "invalid"
+
+		"offline" means the remote processor is powered off.
+
+		"suspended" means that the remote processor is suspended and
+		must be woken to receive messages.
+
+		"running" is the normal state of an available remote processor
+
+		"crashed" indicates that a problem/crash has been detected on
+		the remote processor.
+
+		"invalid" is returned if the remote processor is in an
+		unknown state.
+
+		Writing this file controls the state of the remote processor.
+		The following states can be written:
+
+		- "start"
+		- "stop"
+
+		Writing "start" will attempt to start the processor running the
+		firmware indicated by, or written to,
+		/sys/class/remoteproc/.../firmware. The remote processor should
+		transition to "running" state.
+
+		Writing "stop" will attempt to halt the remote processor and
+		return it to the "offline" state.
+
+What:		/sys/class/remoteproc/.../name
+Date:		August 2019
+KernelVersion:	5.4
+Contact:	Suman Anna <s-anna@ti.com>
+Description:	Remote processor name
+
+		Reports the name of the remote processor. This can be used by
+		userspace in exactly identifying a remote processor and ease
+		up the usage in modifying the 'firmware' or 'state' files.
+
+What:		/sys/class/remoteproc/.../coredump
+Date:		July 2020
+Contact:	Bjorn Andersson <bjorn.andersson@linaro.org>, Ohad Ben-Cohen <ohad@wizery.com>
+Description:	Remote processor coredump configuration
+
+		Reports the coredump configuration of the remote processor,
+		which will be one of:
+
+		"disabled"
+		"enabled"
+		"inline"
+
+		"disabled" means no dump will be collected.
+
+		"enabled" means when the remote processor's coredump is
+		collected it will be copied to a separate buffer and that
+		buffer is exposed to userspace.
+
+		"inline" means when the remote processor's coredump is
+		collected userspace will directly read from the remote
+		processor's device memory. Extra buffer will not be used to
+		copy the dump. Also recovery process will not proceed until
+		all data is read by userspace.
+
+What:		/sys/class/remoteproc/.../recovery
+Date:		July 2020
+Contact:	Bjorn Andersson <bjorn.andersson@linaro.org>, Ohad Ben-Cohen <ohad@wizery.com>
+Description:	Remote processor recovery mechanism
+
+		Reports the recovery mechanism of the remote processor,
+		which will be one of:
+
+		"enabled"
+		"disabled"
+
+		"enabled" means, the remote processor will be automatically
+		recovered whenever it crashes. Moreover, if the remote
+		processor crashes while recovery is disabled, it will
+		be automatically recovered too as soon as recovery is enabled.
+
+		"disabled" means, a remote processor will remain in a crashed
+		state if it crashes. This is useful for debugging purposes;
+		without it, debugging a crash is substantially harder.