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, 116 insertions, 0 deletions

diff --git a/include/math-emu/single.h b/include/math-emu/single.h
new file mode 100644
index 000000000..87f90b0f9
--- /dev/null
+++ b/include/math-emu/single.h
@@ -0,0 +1,116 @@
+/* Software floating-point emulation.
+   Definitions for IEEE Single Precision.
+   Copyright (C) 1997,1998,1999 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Richard Henderson (rth@cygnus.com),
+		  Jakub Jelinek (jj@ultra.linux.cz),
+		  David S. Miller (davem@redhat.com) and
+		  Peter Maydell (pmaydell@chiark.greenend.org.uk).
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If
+   not, write to the Free Software Foundation, Inc.,
+   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+#ifndef    __MATH_EMU_SINGLE_H__
+#define    __MATH_EMU_SINGLE_H__
+
+#if _FP_W_TYPE_SIZE < 32
+#error "Here's a nickel kid.  Go buy yourself a real computer."
+#endif
+
+#define _FP_FRACBITS_S		24
+#define _FP_FRACXBITS_S		(_FP_W_TYPE_SIZE - _FP_FRACBITS_S)
+#define _FP_WFRACBITS_S		(_FP_WORKBITS + _FP_FRACBITS_S)
+#define _FP_WFRACXBITS_S	(_FP_W_TYPE_SIZE - _FP_WFRACBITS_S)
+#define _FP_EXPBITS_S		8
+#define _FP_EXPBIAS_S		127
+#define _FP_EXPMAX_S		255
+#define _FP_QNANBIT_S		((_FP_W_TYPE)1 << (_FP_FRACBITS_S-2))
+#define _FP_IMPLBIT_S		((_FP_W_TYPE)1 << (_FP_FRACBITS_S-1))
+#define _FP_OVERFLOW_S		((_FP_W_TYPE)1 << (_FP_WFRACBITS_S))
+
+/* The implementation of _FP_MUL_MEAT_S and _FP_DIV_MEAT_S should be
+   chosen by the target machine.  */
+
+union _FP_UNION_S
+{
+  float flt;
+  struct {
+#if __BYTE_ORDER == __BIG_ENDIAN
+    unsigned sign : 1;
+    unsigned exp  : _FP_EXPBITS_S;
+    unsigned frac : _FP_FRACBITS_S - (_FP_IMPLBIT_S != 0);
+#else
+    unsigned frac : _FP_FRACBITS_S - (_FP_IMPLBIT_S != 0);
+    unsigned exp  : _FP_EXPBITS_S;
+    unsigned sign : 1;
+#endif
+  } bits __attribute__((packed));
+};
+
+#define FP_DECL_S(X)		_FP_DECL(1,X)
+#define FP_UNPACK_RAW_S(X,val)	_FP_UNPACK_RAW_1(S,X,val)
+#define FP_UNPACK_RAW_SP(X,val)	_FP_UNPACK_RAW_1_P(S,X,val)
+#define FP_PACK_RAW_S(val,X)	_FP_PACK_RAW_1(S,val,X)
+#define FP_PACK_RAW_SP(val,X)		\
+  do {					\
+    if (!FP_INHIBIT_RESULTS)		\
+      _FP_PACK_RAW_1_P(S,val,X);	\
+  } while (0)
+
+#define FP_UNPACK_S(X,val)		\
+  do {					\
+    _FP_UNPACK_RAW_1(S,X,val);		\
+    _FP_UNPACK_CANONICAL(S,1,X);	\
+  } while (0)
+
+#define FP_UNPACK_SP(X,val)		\
+  do {					\
+    _FP_UNPACK_RAW_1_P(S,X,val);	\
+    _FP_UNPACK_CANONICAL(S,1,X);	\
+  } while (0)
+
+#define FP_PACK_S(val,X)		\
+  do {					\
+    _FP_PACK_CANONICAL(S,1,X);		\
+    _FP_PACK_RAW_1(S,val,X);		\
+  } while (0)
+
+#define FP_PACK_SP(val,X)		\
+  do {					\
+    _FP_PACK_CANONICAL(S,1,X);		\
+    if (!FP_INHIBIT_RESULTS)		\
+      _FP_PACK_RAW_1_P(S,val,X);	\
+  } while (0)
+
+#define FP_ISSIGNAN_S(X)		_FP_ISSIGNAN(S,1,X)
+#define FP_NEG_S(R,X)			_FP_NEG(S,1,R,X)
+#define FP_ADD_S(R,X,Y)			_FP_ADD(S,1,R,X,Y)
+#define FP_SUB_S(R,X,Y)			_FP_SUB(S,1,R,X,Y)
+#define FP_MUL_S(R,X,Y)			_FP_MUL(S,1,R,X,Y)
+#define FP_DIV_S(R,X,Y)			_FP_DIV(S,1,R,X,Y)
+#define FP_SQRT_S(R,X)			_FP_SQRT(S,1,R,X)
+#define _FP_SQRT_MEAT_S(R,S,T,X,Q)	_FP_SQRT_MEAT_1(R,S,T,X,Q)
+
+#define FP_CMP_S(r,X,Y,un)	_FP_CMP(S,1,r,X,Y,un)
+#define FP_CMP_EQ_S(r,X,Y)	_FP_CMP_EQ(S,1,r,X,Y)
+
+#define FP_TO_INT_S(r,X,rsz,rsg)	_FP_TO_INT(S,1,r,X,rsz,rsg)
+#define FP_TO_INT_ROUND_S(r,X,rsz,rsg)	_FP_TO_INT_ROUND(S,1,r,X,rsz,rsg)
+#define FP_FROM_INT_S(X,r,rs,rt)	_FP_FROM_INT(S,1,X,r,rs,rt)
+
+#define _FP_FRAC_HIGH_S(X)	_FP_FRAC_HIGH_1(X)
+#define _FP_FRAC_HIGH_RAW_S(X)	_FP_FRAC_HIGH_1(X)
+
+#endif /* __MATH_EMU_SINGLE_H__ */