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, 64 insertions, 0 deletions

diff --git a/arch/powerpc/crypto/Kconfig b/arch/powerpc/crypto/Kconfig
new file mode 100644
index 000000000..b247f7ed9
--- /dev/null
+++ b/arch/powerpc/crypto/Kconfig
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: GPL-2.0
+
+menu "Accelerated Cryptographic Algorithms for CPU (powerpc)"
+
+config CRYPTO_AES_PPC_SPE
+	tristate "Ciphers: AES, modes: ECB/CBC/CTR/XTS (SPE)"
+	depends on SPE
+	select CRYPTO_LIB_AES
+	select CRYPTO_SKCIPHER
+	help
+	  Length-preserving ciphers: AES with ECB, CBC, CTR, and XTS modes
+
+	  Architecture: powerpc using:
+	  - SPE (Signal Processing Engine) extensions
+
+	  SPE is available for:
+	  - Processor Type: Freescale 8500
+	  - CPU selection: e500 (8540)
+
+	  This module should only be used for low power (router) devices
+	  without hardware AES acceleration (e.g. caam crypto). It reduces the
+	  size of the AES tables from 16KB to 8KB + 256 bytes and mitigates
+	  timining attacks. Nevertheless it might be not as secure as other
+	  architecture specific assembler implementations that work on 1KB
+	  tables or 256 bytes S-boxes.
+
+config CRYPTO_AES_GCM_P10
+	tristate "Stitched AES/GCM acceleration support on P10 or later CPU (PPC)"
+	depends on PPC64 && CPU_LITTLE_ENDIAN && VSX
+	select CRYPTO_LIB_AES
+	select CRYPTO_ALGAPI
+	select CRYPTO_AEAD
+	select CRYPTO_SKCIPHER
+	select CRYPTO_SIMD
+	help
+	  AEAD cipher: AES cipher algorithms (FIPS-197)
+	  GCM (Galois/Counter Mode) authenticated encryption mode (NIST SP800-38D)
+	  Architecture: powerpc64 using:
+	    - little-endian
+	    - Power10 or later features
+
+	  Support for cryptographic acceleration instructions on Power10 or
+	  later CPU. This module supports stitched acceleration for AES/GCM.
+
+config CRYPTO_DEV_VMX
+        bool "Support for VMX cryptographic acceleration instructions"
+        depends on PPC64 && VSX
+        help
+          Support for VMX cryptographic acceleration instructions.
+
+config CRYPTO_DEV_VMX_ENCRYPT
+	tristate "Encryption acceleration support on P8 CPU"
+	depends on CRYPTO_DEV_VMX
+	select CRYPTO_AES
+	select CRYPTO_CBC
+	select CRYPTO_CTR
+	select CRYPTO_XTS
+	default m
+	help
+	  Support for VMX cryptographic acceleration instructions on Power8 CPU.
+	  This module supports acceleration for AES in hardware. If you choose
+	  'M' here, this module will be called vmx-crypto.
+
+endmenu