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, 70 insertions, 0 deletions

diff --git a/drivers/scsi/a2091.h b/drivers/scsi/a2091.h
new file mode 100644
index 000000000..8d8a4074a
--- /dev/null
+++ b/drivers/scsi/a2091.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef A2091_H
+#define A2091_H
+
+/* $Id: a2091.h,v 1.4 1997/01/19 23:07:09 davem Exp $
+ *
+ * Header file for the Commodore A2091 Zorro II SCSI controller for Linux
+ *
+ * Written and (C) 1993, Hamish Macdonald, see a2091.c for more info
+ *
+ */
+
+#include <linux/types.h>
+
+#ifndef CMD_PER_LUN
+#define CMD_PER_LUN		2
+#endif
+
+#ifndef CAN_QUEUE
+#define CAN_QUEUE		16
+#endif
+
+/*
+ * if the transfer address ANDed with this results in a non-zero
+ * result, then we can't use DMA.
+ */
+#define A2091_XFER_MASK		(0xff000001)
+
+struct a2091_scsiregs {
+		 unsigned char	pad1[64];
+	volatile unsigned short	ISTR;
+	volatile unsigned short	CNTR;
+		 unsigned char	pad2[60];
+	volatile unsigned int	WTC;
+	volatile unsigned long	ACR;
+		 unsigned char	pad3[6];
+	volatile unsigned short	DAWR;
+		 unsigned char	pad4;
+	volatile unsigned char	SASR;
+		 unsigned char	pad5;
+	volatile unsigned char	SCMD;
+		 unsigned char	pad6[76];
+	volatile unsigned short	ST_DMA;
+	volatile unsigned short	SP_DMA;
+	volatile unsigned short	CINT;
+		 unsigned char	pad7[2];
+	volatile unsigned short	FLUSH;
+};
+
+#define DAWR_A2091		(3)
+
+/* CNTR bits. */
+#define CNTR_TCEN		(1<<7)
+#define CNTR_PREST		(1<<6)
+#define CNTR_PDMD		(1<<5)
+#define CNTR_INTEN		(1<<4)
+#define CNTR_DDIR		(1<<3)
+
+/* ISTR bits. */
+#define ISTR_INTX		(1<<8)
+#define ISTR_INT_F		(1<<7)
+#define ISTR_INTS		(1<<6)
+#define ISTR_E_INT		(1<<5)
+#define ISTR_INT_P		(1<<4)
+#define ISTR_UE_INT		(1<<3)
+#define ISTR_OE_INT		(1<<2)
+#define ISTR_FF_FLG		(1<<1)
+#define ISTR_FE_FLG		(1<<0)
+
+#endif /* A2091_H */