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, 124 insertions, 0 deletions

diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
new file mode 100644
index 000000000..b48491140
--- /dev/null
+++ b/arch/hexagon/Kconfig
@@ -0,0 +1,124 @@
+# SPDX-License-Identifier: GPL-2.0
+# Hexagon configuration
+comment "Linux Kernel Configuration for Hexagon"
+
+config HEXAGON
+	def_bool y
+	select ARCH_32BIT_OFF_T
+	select ARCH_HAS_DELAY_TIMER
+	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
+	select ARCH_NO_PREEMPT
+	select ARCH_WANT_FRAME_POINTERS
+	select DMA_GLOBAL_POOL
+	select HAVE_PAGE_SIZE_4KB
+	select HAVE_PAGE_SIZE_16KB
+	select HAVE_PAGE_SIZE_64KB
+	select HAVE_PAGE_SIZE_256KB
+	select FRAME_POINTER
+	# Other pending projects/to-do items.
+	# select HAVE_REGS_AND_STACK_ACCESS_API
+	# select HAVE_HW_BREAKPOINT if PERF_EVENTS
+	# select ARCH_HAS_CPU_IDLE_WAIT
+	# select GPIOLIB
+	# select HAVE_CLK
+	select GENERIC_ATOMIC64
+	select HAVE_PERF_EVENTS
+	# GENERIC_ALLOCATOR is used by dma_alloc_coherent()
+	select GENERIC_ALLOCATOR
+	select GENERIC_IRQ_PROBE
+	select GENERIC_IRQ_SHOW
+	select HAVE_ARCH_KGDB
+	select HAVE_ARCH_TRACEHOOK
+	select NEED_SG_DMA_LENGTH
+	select GENERIC_IOREMAP
+	select GENERIC_SMP_IDLE_THREAD
+	select STACKTRACE_SUPPORT
+	select GENERIC_CLOCKEVENTS_BROADCAST
+	select LOCK_MM_AND_FIND_VMA
+	select MODULES_USE_ELF_RELA
+	select GENERIC_CPU_DEVICES
+	select ARCH_WANT_LD_ORPHAN_WARN
+	select TRACE_IRQFLAGS_SUPPORT
+	help
+	  Qualcomm Hexagon is a processor architecture designed for high
+	  performance and low power across a wide variety of applications.
+
+config HEXAGON_PHYS_OFFSET
+	def_bool y
+	help
+	  Platforms that don't load the kernel at zero set this.
+
+config LOCKDEP_SUPPORT
+	def_bool y
+
+config EARLY_PRINTK
+	def_bool y
+
+config MMU
+	def_bool y
+
+config NO_IOPORT_MAP
+	def_bool y
+
+config GENERIC_CSUM
+	def_bool y
+
+config GENERIC_HWEIGHT
+	def_bool y
+
+config STACKTRACE_SUPPORT
+	def_bool y
+	select STACKTRACE
+
+config GENERIC_BUG
+	def_bool y
+	depends on BUG
+
+menu "Machine selection"
+
+choice
+	prompt "System type"
+	default HEXAGON_COMET
+
+config HEXAGON_COMET
+	bool "Comet Board"
+	help
+	  Support for the Comet platform.
+
+endchoice
+
+config HEXAGON_ARCH_VERSION
+	int "Architecture version"
+	default 2
+
+config CMDLINE
+	string "Default kernel command string"
+	default ""
+	help
+	  On some platforms, there is currently no way for the boot loader
+	  to pass arguments to the kernel. For these, you should supply some
+	  command-line options at build time by entering them here.  At a
+	  minimum, you should specify the memory size and the root device
+	  (e.g., mem=64M root=/dev/nfs).
+
+config SMP
+	bool "Multi-Processing support"
+	help
+	  Enables SMP support in the kernel.  If unsure, say "Y"
+
+config NR_CPUS
+	int "Maximum number of CPUs" if SMP
+	range 2 6 if SMP
+	default "1" if !SMP
+	default "6" if SMP
+	help
+	  This allows you to specify the maximum number of CPUs which this
+	  kernel will support.  The maximum supported value is 6 and the
+	  minimum value which makes sense is 2.
+
+	  This is purely to save memory - each supported CPU adds
+	  approximately eight kilobytes to the kernel image.
+
+source "kernel/Kconfig.hz"
+
+endmenu