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, 161 insertions, 0 deletions

diff --git a/arch/mips/kvm/msa.S b/arch/mips/kvm/msa.S
new file mode 100644
index 000000000..d02f0c6cc
--- /dev/null
+++ b/arch/mips/kvm/msa.S
@@ -0,0 +1,161 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * MIPS SIMD Architecture (MSA) context handling code for KVM.
+ *
+ * Copyright (C) 2015 Imagination Technologies Ltd.
+ */
+
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/asmmacro.h>
+#include <asm/regdef.h>
+
+	.set	noreorder
+	.set	noat
+
+LEAF(__kvm_save_msa)
+	st_d	0,  VCPU_FPR0,  a0
+	st_d	1,  VCPU_FPR1,  a0
+	st_d	2,  VCPU_FPR2,  a0
+	st_d	3,  VCPU_FPR3,  a0
+	st_d	4,  VCPU_FPR4,  a0
+	st_d	5,  VCPU_FPR5,  a0
+	st_d	6,  VCPU_FPR6,  a0
+	st_d	7,  VCPU_FPR7,  a0
+	st_d	8,  VCPU_FPR8,  a0
+	st_d	9,  VCPU_FPR9,  a0
+	st_d	10, VCPU_FPR10, a0
+	st_d	11, VCPU_FPR11, a0
+	st_d	12, VCPU_FPR12, a0
+	st_d	13, VCPU_FPR13, a0
+	st_d	14, VCPU_FPR14, a0
+	st_d	15, VCPU_FPR15, a0
+	st_d	16, VCPU_FPR16, a0
+	st_d	17, VCPU_FPR17, a0
+	st_d	18, VCPU_FPR18, a0
+	st_d	19, VCPU_FPR19, a0
+	st_d	20, VCPU_FPR20, a0
+	st_d	21, VCPU_FPR21, a0
+	st_d	22, VCPU_FPR22, a0
+	st_d	23, VCPU_FPR23, a0
+	st_d	24, VCPU_FPR24, a0
+	st_d	25, VCPU_FPR25, a0
+	st_d	26, VCPU_FPR26, a0
+	st_d	27, VCPU_FPR27, a0
+	st_d	28, VCPU_FPR28, a0
+	st_d	29, VCPU_FPR29, a0
+	st_d	30, VCPU_FPR30, a0
+	st_d	31, VCPU_FPR31, a0
+	jr	ra
+	 nop
+	END(__kvm_save_msa)
+
+LEAF(__kvm_restore_msa)
+	ld_d	0,  VCPU_FPR0,  a0
+	ld_d	1,  VCPU_FPR1,  a0
+	ld_d	2,  VCPU_FPR2,  a0
+	ld_d	3,  VCPU_FPR3,  a0
+	ld_d	4,  VCPU_FPR4,  a0
+	ld_d	5,  VCPU_FPR5,  a0
+	ld_d	6,  VCPU_FPR6,  a0
+	ld_d	7,  VCPU_FPR7,  a0
+	ld_d	8,  VCPU_FPR8,  a0
+	ld_d	9,  VCPU_FPR9,  a0
+	ld_d	10, VCPU_FPR10, a0
+	ld_d	11, VCPU_FPR11, a0
+	ld_d	12, VCPU_FPR12, a0
+	ld_d	13, VCPU_FPR13, a0
+	ld_d	14, VCPU_FPR14, a0
+	ld_d	15, VCPU_FPR15, a0
+	ld_d	16, VCPU_FPR16, a0
+	ld_d	17, VCPU_FPR17, a0
+	ld_d	18, VCPU_FPR18, a0
+	ld_d	19, VCPU_FPR19, a0
+	ld_d	20, VCPU_FPR20, a0
+	ld_d	21, VCPU_FPR21, a0
+	ld_d	22, VCPU_FPR22, a0
+	ld_d	23, VCPU_FPR23, a0
+	ld_d	24, VCPU_FPR24, a0
+	ld_d	25, VCPU_FPR25, a0
+	ld_d	26, VCPU_FPR26, a0
+	ld_d	27, VCPU_FPR27, a0
+	ld_d	28, VCPU_FPR28, a0
+	ld_d	29, VCPU_FPR29, a0
+	ld_d	30, VCPU_FPR30, a0
+	ld_d	31, VCPU_FPR31, a0
+	jr	ra
+	 nop
+	END(__kvm_restore_msa)
+
+	.macro	kvm_restore_msa_upper	wr, off, base
+	.set	push
+	.set	noat
+#ifdef CONFIG_64BIT
+	ld	$1, \off(\base)
+	insert_d \wr, 1
+#elif defined(CONFIG_CPU_LITTLE_ENDIAN)
+	lw	$1, \off(\base)
+	insert_w \wr, 2
+	lw	$1, (\off+4)(\base)
+	insert_w \wr, 3
+#else /* CONFIG_CPU_BIG_ENDIAN */
+	lw	$1, (\off+4)(\base)
+	insert_w \wr, 2
+	lw	$1, \off(\base)
+	insert_w \wr, 3
+#endif
+	.set	pop
+	.endm
+
+LEAF(__kvm_restore_msa_upper)
+	kvm_restore_msa_upper	0,  VCPU_FPR0 +8, a0
+	kvm_restore_msa_upper	1,  VCPU_FPR1 +8, a0
+	kvm_restore_msa_upper	2,  VCPU_FPR2 +8, a0
+	kvm_restore_msa_upper	3,  VCPU_FPR3 +8, a0
+	kvm_restore_msa_upper	4,  VCPU_FPR4 +8, a0
+	kvm_restore_msa_upper	5,  VCPU_FPR5 +8, a0
+	kvm_restore_msa_upper	6,  VCPU_FPR6 +8, a0
+	kvm_restore_msa_upper	7,  VCPU_FPR7 +8, a0
+	kvm_restore_msa_upper	8,  VCPU_FPR8 +8, a0
+	kvm_restore_msa_upper	9,  VCPU_FPR9 +8, a0
+	kvm_restore_msa_upper	10, VCPU_FPR10+8, a0
+	kvm_restore_msa_upper	11, VCPU_FPR11+8, a0
+	kvm_restore_msa_upper	12, VCPU_FPR12+8, a0
+	kvm_restore_msa_upper	13, VCPU_FPR13+8, a0
+	kvm_restore_msa_upper	14, VCPU_FPR14+8, a0
+	kvm_restore_msa_upper	15, VCPU_FPR15+8, a0
+	kvm_restore_msa_upper	16, VCPU_FPR16+8, a0
+	kvm_restore_msa_upper	17, VCPU_FPR17+8, a0
+	kvm_restore_msa_upper	18, VCPU_FPR18+8, a0
+	kvm_restore_msa_upper	19, VCPU_FPR19+8, a0
+	kvm_restore_msa_upper	20, VCPU_FPR20+8, a0
+	kvm_restore_msa_upper	21, VCPU_FPR21+8, a0
+	kvm_restore_msa_upper	22, VCPU_FPR22+8, a0
+	kvm_restore_msa_upper	23, VCPU_FPR23+8, a0
+	kvm_restore_msa_upper	24, VCPU_FPR24+8, a0
+	kvm_restore_msa_upper	25, VCPU_FPR25+8, a0
+	kvm_restore_msa_upper	26, VCPU_FPR26+8, a0
+	kvm_restore_msa_upper	27, VCPU_FPR27+8, a0
+	kvm_restore_msa_upper	28, VCPU_FPR28+8, a0
+	kvm_restore_msa_upper	29, VCPU_FPR29+8, a0
+	kvm_restore_msa_upper	30, VCPU_FPR30+8, a0
+	kvm_restore_msa_upper	31, VCPU_FPR31+8, a0
+	jr	ra
+	 nop
+	END(__kvm_restore_msa_upper)
+
+LEAF(__kvm_restore_msacsr)
+	lw	t0, VCPU_MSA_CSR(a0)
+	/*
+	 * The ctcmsa must stay at this offset in __kvm_restore_msacsr.
+	 * See kvm_mips_csr_die_notify() which handles t0 containing a value
+	 * which triggers an MSA FP Exception, which must be stepped over and
+	 * ignored since the set cause bits must remain there for the guest.
+	 */
+	_ctcmsa	MSA_CSR, t0
+	jr	ra
+	 nop
+	END(__kvm_restore_msacsr)