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, 542 insertions, 0 deletions

diff --git a/arch/xtensa/lib/memcopy.S b/arch/xtensa/lib/memcopy.S
new file mode 100644
index 000000000..f60760396
--- /dev/null
+++ b/arch/xtensa/lib/memcopy.S
@@ -0,0 +1,542 @@
+/*
+ * arch/xtensa/lib/hal/memcopy.S -- Core HAL library functions
+ * xthal_memcpy and xthal_bcopy
+ *
+ * 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.
+ *
+ * Copyright (C) 2002 - 2012 Tensilica Inc.
+ */
+
+#include <linux/linkage.h>
+#include <asm/asmmacro.h>
+#include <asm/core.h>
+
+/*
+ * void *memcpy(void *dst, const void *src, size_t len);
+ *
+ * This function is intended to do the same thing as the standard
+ * library function memcpy() for most cases.
+ * However, where the source and/or destination references
+ * an instruction RAM or ROM or a data RAM or ROM, that
+ * source and/or destination will always be accessed with
+ * 32-bit load and store instructions (as required for these
+ * types of devices).
+ *
+ * !!!!!!!  XTFIXME:
+ * !!!!!!!  Handling of IRAM/IROM has not yet
+ * !!!!!!!  been implemented.
+ *
+ * The (general case) algorithm is as follows:
+ *   If destination is unaligned, align it by conditionally
+ *     copying 1 and 2 bytes.
+ *   If source is aligned,
+ *     do 16 bytes with a loop, and then finish up with
+ *     8, 4, 2, and 1 byte copies conditional on the length;
+ *   else (if source is unaligned),
+ *     do the same, but use SRC to align the source data.
+ *   This code tries to use fall-through branches for the common
+ *     case of aligned source and destination and multiple
+ *     of 4 (or 8) length.
+ *
+ * Register use:
+ *	a0/ return address
+ *	a1/ stack pointer
+ *	a2/ return value
+ *	a3/ src
+ *	a4/ length
+ *	a5/ dst
+ *	a6/ tmp
+ *	a7/ tmp
+ *	a8/ tmp
+ *	a9/ tmp
+ *	a10/ tmp
+ *	a11/ tmp
+ */
+
+	.text
+
+/*
+ * Byte by byte copy
+ */
+	.align	4
+	.byte	0		# 1 mod 4 alignment for LOOPNEZ
+				# (0 mod 4 alignment for LBEG)
+.Lbytecopy:
+#if XCHAL_HAVE_LOOPS
+	loopnez	a4, .Lbytecopydone
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a4, .Lbytecopydone
+	add	a7, a3, a4	# a7 = end address for source
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lnextbyte:
+	l8ui	a6, a3, 0
+	addi	a3, a3, 1
+	s8i	a6, a5, 0
+	addi	a5, a5, 1
+#if !XCHAL_HAVE_LOOPS
+	bne	a3, a7, .Lnextbyte # continue loop if $a3:src != $a7:src_end
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lbytecopydone:
+	abi_ret_default
+
+/*
+ * Destination is unaligned
+ */
+
+	.align	4
+.Ldst1mod2:	# dst is only byte aligned
+	_bltui	a4, 7, .Lbytecopy	# do short copies byte by byte
+
+	# copy 1 byte
+	l8ui	a6, a3,  0
+	addi	a3, a3,  1
+	addi	a4, a4, -1
+	s8i	a6, a5,  0
+	addi	a5, a5,  1
+	_bbci.l	a5, 1, .Ldstaligned	# if dst is now aligned, then
+					# return to main algorithm
+.Ldst2mod4:	# dst 16-bit aligned
+	# copy 2 bytes
+	_bltui	a4, 6, .Lbytecopy	# do short copies byte by byte
+	l8ui	a6, a3,  0
+	l8ui	a7, a3,  1
+	addi	a3, a3,  2
+	addi	a4, a4, -2
+	s8i	a6, a5,  0
+	s8i	a7, a5,  1
+	addi	a5, a5,  2
+	j	.Ldstaligned	# dst is now aligned, return to main algorithm
+
+ENTRY(__memcpy)
+WEAK(memcpy)
+
+	abi_entry_default
+	# a2/ dst, a3/ src, a4/ len
+	mov	a5, a2		# copy dst so that a2 is return value
+.Lcommon:
+	_bbsi.l	a2, 0, .Ldst1mod2	# if dst is 1 mod 2
+	_bbsi.l	a2, 1, .Ldst2mod4	# if dst is 2 mod 4
+.Ldstaligned:	# return here from .Ldst?mod? once dst is aligned
+	srli	a7, a4, 4	# number of loop iterations with 16B
+				# per iteration
+	movi	a8, 3		# if source is not aligned,
+	_bany	a3, a8, .Lsrcunaligned	# then use shifting copy
+	/*
+	 * Destination and source are word-aligned, use word copy.
+	 */
+	# copy 16 bytes per iteration for word-aligned dst and word-aligned src
+#if XCHAL_HAVE_LOOPS
+	loopnez	a7, .Loop1done
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a7, .Loop1done
+	slli	a8, a7, 4
+	add	a8, a8, a3	# a8 = end of last 16B source chunk
+#endif /* !XCHAL_HAVE_LOOPS */
+.Loop1:
+	l32i	a6, a3,  0
+	l32i	a7, a3,  4
+	s32i	a6, a5,  0
+	l32i	a6, a3,  8
+	s32i	a7, a5,  4
+	l32i	a7, a3, 12
+	s32i	a6, a5,  8
+	addi	a3, a3, 16
+	s32i	a7, a5, 12
+	addi	a5, a5, 16
+#if !XCHAL_HAVE_LOOPS
+	bne	a3, a8, .Loop1  # continue loop if a3:src != a8:src_end
+#endif /* !XCHAL_HAVE_LOOPS */
+.Loop1done:
+	bbci.l	a4, 3, .L2
+	# copy 8 bytes
+	l32i	a6, a3,  0
+	l32i	a7, a3,  4
+	addi	a3, a3,  8
+	s32i	a6, a5,  0
+	s32i	a7, a5,  4
+	addi	a5, a5,  8
+.L2:
+	bbsi.l	a4, 2, .L3
+	bbsi.l	a4, 1, .L4
+	bbsi.l	a4, 0, .L5
+	abi_ret_default
+.L3:
+	# copy 4 bytes
+	l32i	a6, a3,  0
+	addi	a3, a3,  4
+	s32i	a6, a5,  0
+	addi	a5, a5,  4
+	bbsi.l	a4, 1, .L4
+	bbsi.l	a4, 0, .L5
+	abi_ret_default
+.L4:
+	# copy 2 bytes
+	l16ui	a6, a3,  0
+	addi	a3, a3,  2
+	s16i	a6, a5,  0
+	addi	a5, a5,  2
+	bbsi.l	a4, 0, .L5
+	abi_ret_default
+.L5:
+	# copy 1 byte
+	l8ui	a6, a3,  0
+	s8i	a6, a5,  0
+	abi_ret_default
+
+/*
+ * Destination is aligned, Source is unaligned
+ */
+
+	.align	4
+.Lsrcunaligned:
+	_beqz	a4, .Ldone	# avoid loading anything for zero-length copies
+	# copy 16 bytes per iteration for word-aligned dst and unaligned src
+	__ssa8	a3		# set shift amount from byte offset
+
+/* set to 1 when running on ISS (simulator) with the
+   lint or ferret client, or 0 to save a few cycles */
+#define SIM_CHECKS_ALIGNMENT	1
+#if XCHAL_UNALIGNED_LOAD_EXCEPTION || SIM_CHECKS_ALIGNMENT
+	and	a11, a3, a8	# save unalignment offset for below
+	sub	a3, a3, a11	# align a3
+#endif
+	l32i	a6, a3, 0	# load first word
+#if XCHAL_HAVE_LOOPS
+	loopnez	a7, .Loop2done
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a7, .Loop2done
+	slli	a10, a7, 4
+	add	a10, a10, a3	# a10 = end of last 16B source chunk
+#endif /* !XCHAL_HAVE_LOOPS */
+.Loop2:
+	l32i	a7, a3,  4
+	l32i	a8, a3,  8
+	__src_b	a6, a6, a7
+	s32i	a6, a5,  0
+	l32i	a9, a3, 12
+	__src_b	a7, a7, a8
+	s32i	a7, a5,  4
+	l32i	a6, a3, 16
+	__src_b	a8, a8, a9
+	s32i	a8, a5,  8
+	addi	a3, a3, 16
+	__src_b	a9, a9, a6
+	s32i	a9, a5, 12
+	addi	a5, a5, 16
+#if !XCHAL_HAVE_LOOPS
+	bne	a3, a10, .Loop2 # continue loop if a3:src != a10:src_end
+#endif /* !XCHAL_HAVE_LOOPS */
+.Loop2done:
+	bbci.l	a4, 3, .L12
+	# copy 8 bytes
+	l32i	a7, a3,  4
+	l32i	a8, a3,  8
+	__src_b	a6, a6, a7
+	s32i	a6, a5,  0
+	addi	a3, a3,  8
+	__src_b	a7, a7, a8
+	s32i	a7, a5,  4
+	addi	a5, a5,  8
+	mov	a6, a8
+.L12:
+	bbci.l	a4, 2, .L13
+	# copy 4 bytes
+	l32i	a7, a3,  4
+	addi	a3, a3,  4
+	__src_b	a6, a6, a7
+	s32i	a6, a5,  0
+	addi	a5, a5,  4
+	mov	a6, a7
+.L13:
+#if XCHAL_UNALIGNED_LOAD_EXCEPTION || SIM_CHECKS_ALIGNMENT
+	add	a3, a3, a11	# readjust a3 with correct misalignment
+#endif
+	bbsi.l	a4, 1, .L14
+	bbsi.l	a4, 0, .L15
+.Ldone:	abi_ret_default
+.L14:
+	# copy 2 bytes
+	l8ui	a6, a3,  0
+	l8ui	a7, a3,  1
+	addi	a3, a3,  2
+	s8i	a6, a5,  0
+	s8i	a7, a5,  1
+	addi	a5, a5,  2
+	bbsi.l	a4, 0, .L15
+	abi_ret_default
+.L15:
+	# copy 1 byte
+	l8ui	a6, a3,  0
+	s8i	a6, a5,  0
+	abi_ret_default
+
+ENDPROC(__memcpy)
+EXPORT_SYMBOL(__memcpy)
+EXPORT_SYMBOL(memcpy)
+
+/*
+ * void *memmove(void *dst, const void *src, size_t len);
+ *
+ * This function is intended to do the same thing as the standard
+ * library function memmove() for most cases.
+ * However, where the source and/or destination references
+ * an instruction RAM or ROM or a data RAM or ROM, that
+ * source and/or destination will always be accessed with
+ * 32-bit load and store instructions (as required for these
+ * types of devices).
+ *
+ * !!!!!!!  XTFIXME:
+ * !!!!!!!  Handling of IRAM/IROM has not yet
+ * !!!!!!!  been implemented.
+ *
+ * The (general case) algorithm is as follows:
+ *   If end of source doesn't overlap destination then use memcpy.
+ *   Otherwise do memcpy backwards.
+ *
+ * Register use:
+ *	a0/ return address
+ *	a1/ stack pointer
+ *	a2/ return value
+ *	a3/ src
+ *	a4/ length
+ *	a5/ dst
+ *	a6/ tmp
+ *	a7/ tmp
+ *	a8/ tmp
+ *	a9/ tmp
+ *	a10/ tmp
+ *	a11/ tmp
+ */
+
+/*
+ * Byte by byte copy
+ */
+	.align	4
+	.byte	0		# 1 mod 4 alignment for LOOPNEZ
+				# (0 mod 4 alignment for LBEG)
+.Lbackbytecopy:
+#if XCHAL_HAVE_LOOPS
+	loopnez	a4, .Lbackbytecopydone
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a4, .Lbackbytecopydone
+	sub	a7, a3, a4	# a7 = start address for source
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lbacknextbyte:
+	addi	a3, a3, -1
+	l8ui	a6, a3, 0
+	addi	a5, a5, -1
+	s8i	a6, a5, 0
+#if !XCHAL_HAVE_LOOPS
+	bne	a3, a7, .Lbacknextbyte # continue loop if
+				       # $a3:src != $a7:src_start
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lbackbytecopydone:
+	abi_ret_default
+
+/*
+ * Destination is unaligned
+ */
+
+	.align	4
+.Lbackdst1mod2:	# dst is only byte aligned
+	_bltui	a4, 7, .Lbackbytecopy	# do short copies byte by byte
+
+	# copy 1 byte
+	addi	a3, a3, -1
+	l8ui	a6, a3,  0
+	addi	a5, a5, -1
+	s8i	a6, a5,  0
+	addi	a4, a4, -1
+	_bbci.l	a5, 1, .Lbackdstaligned	# if dst is now aligned, then
+					# return to main algorithm
+.Lbackdst2mod4:	# dst 16-bit aligned
+	# copy 2 bytes
+	_bltui	a4, 6, .Lbackbytecopy	# do short copies byte by byte
+	addi	a3, a3, -2
+	l8ui	a6, a3,  0
+	l8ui	a7, a3,  1
+	addi	a5, a5, -2
+	s8i	a6, a5,  0
+	s8i	a7, a5,  1
+	addi	a4, a4, -2
+	j	.Lbackdstaligned	# dst is now aligned,
+					# return to main algorithm
+
+ENTRY(__memmove)
+WEAK(memmove)
+
+	abi_entry_default
+	# a2/ dst, a3/ src, a4/ len
+	mov	a5, a2		# copy dst so that a2 is return value
+.Lmovecommon:
+	sub	a6, a5, a3
+	bgeu	a6, a4, .Lcommon
+
+	add	a5, a5, a4
+	add	a3, a3, a4
+
+	_bbsi.l	a5, 0, .Lbackdst1mod2	# if dst is 1 mod 2
+	_bbsi.l	a5, 1, .Lbackdst2mod4	# if dst is 2 mod 4
+.Lbackdstaligned:	# return here from .Lbackdst?mod? once dst is aligned
+	srli	a7, a4, 4	# number of loop iterations with 16B
+				# per iteration
+	movi	a8, 3		# if source is not aligned,
+	_bany	a3, a8, .Lbacksrcunaligned	# then use shifting copy
+	/*
+	 * Destination and source are word-aligned, use word copy.
+	 */
+	# copy 16 bytes per iteration for word-aligned dst and word-aligned src
+#if XCHAL_HAVE_LOOPS
+	loopnez	a7, .LbackLoop1done
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a7, .LbackLoop1done
+	slli	a8, a7, 4
+	sub	a8, a3, a8	# a8 = start of first 16B source chunk
+#endif /* !XCHAL_HAVE_LOOPS */
+.LbackLoop1:
+	addi	a3, a3, -16
+	l32i	a7, a3, 12
+	l32i	a6, a3,  8
+	addi	a5, a5, -16
+	s32i	a7, a5, 12
+	l32i	a7, a3,  4
+	s32i	a6, a5,  8
+	l32i	a6, a3,  0
+	s32i	a7, a5,  4
+	s32i	a6, a5,  0
+#if !XCHAL_HAVE_LOOPS
+	bne	a3, a8, .LbackLoop1  # continue loop if a3:src != a8:src_start
+#endif /* !XCHAL_HAVE_LOOPS */
+.LbackLoop1done:
+	bbci.l	a4, 3, .Lback2
+	# copy 8 bytes
+	addi	a3, a3, -8
+	l32i	a6, a3,  0
+	l32i	a7, a3,  4
+	addi	a5, a5, -8
+	s32i	a6, a5,  0
+	s32i	a7, a5,  4
+.Lback2:
+	bbsi.l	a4, 2, .Lback3
+	bbsi.l	a4, 1, .Lback4
+	bbsi.l	a4, 0, .Lback5
+	abi_ret_default
+.Lback3:
+	# copy 4 bytes
+	addi	a3, a3, -4
+	l32i	a6, a3,  0
+	addi	a5, a5, -4
+	s32i	a6, a5,  0
+	bbsi.l	a4, 1, .Lback4
+	bbsi.l	a4, 0, .Lback5
+	abi_ret_default
+.Lback4:
+	# copy 2 bytes
+	addi	a3, a3, -2
+	l16ui	a6, a3,  0
+	addi	a5, a5, -2
+	s16i	a6, a5,  0
+	bbsi.l	a4, 0, .Lback5
+	abi_ret_default
+.Lback5:
+	# copy 1 byte
+	addi	a3, a3, -1
+	l8ui	a6, a3,  0
+	addi	a5, a5, -1
+	s8i	a6, a5,  0
+	abi_ret_default
+
+/*
+ * Destination is aligned, Source is unaligned
+ */
+
+	.align	4
+.Lbacksrcunaligned:
+	_beqz	a4, .Lbackdone	# avoid loading anything for zero-length copies
+	# copy 16 bytes per iteration for word-aligned dst and unaligned src
+	__ssa8	a3		# set shift amount from byte offset
+#define SIM_CHECKS_ALIGNMENT	1	/* set to 1 when running on ISS with
+					 * the lint or ferret client, or 0
+					 * to save a few cycles */
+#if XCHAL_UNALIGNED_LOAD_EXCEPTION || SIM_CHECKS_ALIGNMENT
+	and	a11, a3, a8	# save unalignment offset for below
+	sub	a3, a3, a11	# align a3
+#endif
+	l32i	a6, a3, 0	# load first word
+#if XCHAL_HAVE_LOOPS
+	loopnez	a7, .LbackLoop2done
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a7, .LbackLoop2done
+	slli	a10, a7, 4
+	sub	a10, a3, a10	# a10 = start of first 16B source chunk
+#endif /* !XCHAL_HAVE_LOOPS */
+.LbackLoop2:
+	addi	a3, a3, -16
+	l32i	a7, a3, 12
+	l32i	a8, a3,  8
+	addi	a5, a5, -16
+	__src_b	a6, a7, a6
+	s32i	a6, a5, 12
+	l32i	a9, a3,  4
+	__src_b	a7, a8, a7
+	s32i	a7, a5,  8
+	l32i	a6, a3,  0
+	__src_b	a8, a9, a8
+	s32i	a8, a5,  4
+	__src_b	a9, a6, a9
+	s32i	a9, a5,  0
+#if !XCHAL_HAVE_LOOPS
+	bne	a3, a10, .LbackLoop2 # continue loop if a3:src != a10:src_start
+#endif /* !XCHAL_HAVE_LOOPS */
+.LbackLoop2done:
+	bbci.l	a4, 3, .Lback12
+	# copy 8 bytes
+	addi	a3, a3, -8
+	l32i	a7, a3,  4
+	l32i	a8, a3,  0
+	addi	a5, a5, -8
+	__src_b	a6, a7, a6
+	s32i	a6, a5,  4
+	__src_b	a7, a8, a7
+	s32i	a7, a5,  0
+	mov	a6, a8
+.Lback12:
+	bbci.l	a4, 2, .Lback13
+	# copy 4 bytes
+	addi	a3, a3, -4
+	l32i	a7, a3,  0
+	addi	a5, a5, -4
+	__src_b	a6, a7, a6
+	s32i	a6, a5,  0
+	mov	a6, a7
+.Lback13:
+#if XCHAL_UNALIGNED_LOAD_EXCEPTION || SIM_CHECKS_ALIGNMENT
+	add	a3, a3, a11	# readjust a3 with correct misalignment
+#endif
+	bbsi.l	a4, 1, .Lback14
+	bbsi.l	a4, 0, .Lback15
+.Lbackdone:
+	abi_ret_default
+.Lback14:
+	# copy 2 bytes
+	addi	a3, a3, -2
+	l8ui	a6, a3,  0
+	l8ui	a7, a3,  1
+	addi	a5, a5, -2
+	s8i	a6, a5,  0
+	s8i	a7, a5,  1
+	bbsi.l	a4, 0, .Lback15
+	abi_ret_default
+.Lback15:
+	# copy 1 byte
+	addi	a3, a3, -1
+	addi	a5, a5, -1
+	l8ui	a6, a3,  0
+	s8i	a6, a5,  0
+	abi_ret_default
+
+ENDPROC(__memmove)
+EXPORT_SYMBOL(__memmove)
+EXPORT_SYMBOL(memmove)