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, 188 insertions, 0 deletions

diff --git a/arch/m68k/mac/oss.c b/arch/m68k/mac/oss.c
new file mode 100644
index 000000000..1641607f3
--- /dev/null
+++ b/arch/m68k/mac/oss.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	Operating System Services (OSS) chip handling
+ *	Written by Joshua M. Thompson (funaho@jurai.org)
+ *
+ *
+ *	This chip is used in the IIfx in place of VIA #2. It acts like a fancy
+ *	VIA chip with prorammable interrupt levels.
+ *
+ * 990502 (jmt) - Major rewrite for new interrupt architecture as well as some
+ *		  recent insights into OSS operational details.
+ * 990610 (jmt) - Now taking full advantage of the OSS. Interrupts are mapped
+ *		  to mostly match the A/UX interrupt scheme supported on the
+ *		  VIA side. Also added support for enabling the ISM irq again
+ *		  since we now have a functional IOP manager.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/irq.h>
+
+#include <asm/macintosh.h>
+#include <asm/macints.h>
+#include <asm/mac_via.h>
+#include <asm/mac_oss.h>
+
+#include "mac.h"
+
+int oss_present;
+volatile struct mac_oss *oss;
+
+/*
+ * Initialize the OSS
+ */
+
+void __init oss_init(void)
+{
+	int i;
+
+	if (macintosh_config->ident != MAC_MODEL_IIFX)
+		return;
+
+	oss = (struct mac_oss *) OSS_BASE;
+	pr_debug("OSS detected at %p", oss);
+	oss_present = 1;
+
+	/* Disable all interrupts. Unlike a VIA it looks like we    */
+	/* do this by setting the source's interrupt level to zero. */
+
+	for (i = 0; i < OSS_NUM_SOURCES; i++)
+		oss->irq_level[i] = 0;
+}
+
+/*
+ * Handle OSS interrupts.
+ * XXX how do you clear a pending IRQ? is it even necessary?
+ */
+
+static void oss_iopism_irq(struct irq_desc *desc)
+{
+	generic_handle_irq(IRQ_MAC_ADB);
+}
+
+static void oss_scsi_irq(struct irq_desc *desc)
+{
+	generic_handle_irq(IRQ_MAC_SCSI);
+}
+
+static void oss_nubus_irq(struct irq_desc *desc)
+{
+	u16 events, irq_bit;
+	int irq_num;
+
+	events = oss->irq_pending & OSS_IP_NUBUS;
+	irq_num = NUBUS_SOURCE_BASE + 5;
+	irq_bit = OSS_IP_NUBUS5;
+	do {
+		if (events & irq_bit) {
+			events &= ~irq_bit;
+			generic_handle_irq(irq_num);
+		}
+		--irq_num;
+		irq_bit >>= 1;
+	} while (events);
+}
+
+static void oss_iopscc_irq(struct irq_desc *desc)
+{
+	generic_handle_irq(IRQ_MAC_SCC);
+}
+
+/*
+ * Register the OSS and NuBus interrupt dispatchers.
+ *
+ * This IRQ mapping is laid out with two things in mind: first, we try to keep
+ * things on their own levels to avoid having to do double-dispatches. Second,
+ * the levels match as closely as possible the alternate IRQ mapping mode (aka
+ * "A/UX mode") available on some VIA machines.
+ */
+
+#define OSS_IRQLEV_IOPISM    IRQ_AUTO_1
+#define OSS_IRQLEV_SCSI      IRQ_AUTO_2
+#define OSS_IRQLEV_NUBUS     IRQ_AUTO_3
+#define OSS_IRQLEV_IOPSCC    IRQ_AUTO_4
+#define OSS_IRQLEV_VIA1      IRQ_AUTO_6
+
+void __init oss_register_interrupts(void)
+{
+	irq_set_chained_handler(OSS_IRQLEV_IOPISM, oss_iopism_irq);
+	irq_set_chained_handler(OSS_IRQLEV_SCSI,   oss_scsi_irq);
+	irq_set_chained_handler(OSS_IRQLEV_NUBUS,  oss_nubus_irq);
+	irq_set_chained_handler(OSS_IRQLEV_IOPSCC, oss_iopscc_irq);
+	irq_set_chained_handler(OSS_IRQLEV_VIA1,   via1_irq);
+
+	/* OSS_VIA1 gets enabled here because it has no machspec interrupt. */
+	oss->irq_level[OSS_VIA1] = OSS_IRQLEV_VIA1;
+}
+
+/*
+ * Enable an OSS interrupt
+ *
+ * It looks messy but it's rather straightforward. The switch() statement
+ * just maps the machspec interrupt numbers to the right OSS interrupt
+ * source (if the OSS handles that interrupt) and then sets the interrupt
+ * level for that source to nonzero, thus enabling the interrupt.
+ */
+
+void oss_irq_enable(int irq) {
+	switch(irq) {
+		case IRQ_MAC_SCC:
+			oss->irq_level[OSS_IOPSCC] = OSS_IRQLEV_IOPSCC;
+			return;
+		case IRQ_MAC_ADB:
+			oss->irq_level[OSS_IOPISM] = OSS_IRQLEV_IOPISM;
+			return;
+		case IRQ_MAC_SCSI:
+			oss->irq_level[OSS_SCSI] = OSS_IRQLEV_SCSI;
+			return;
+		case IRQ_NUBUS_9:
+		case IRQ_NUBUS_A:
+		case IRQ_NUBUS_B:
+		case IRQ_NUBUS_C:
+		case IRQ_NUBUS_D:
+		case IRQ_NUBUS_E:
+			irq -= NUBUS_SOURCE_BASE;
+			oss->irq_level[irq] = OSS_IRQLEV_NUBUS;
+			return;
+	}
+
+	if (IRQ_SRC(irq) == 1)
+		via_irq_enable(irq);
+}
+
+/*
+ * Disable an OSS interrupt
+ *
+ * Same as above except we set the source's interrupt level to zero,
+ * to disable the interrupt.
+ */
+
+void oss_irq_disable(int irq) {
+	switch(irq) {
+		case IRQ_MAC_SCC:
+			oss->irq_level[OSS_IOPSCC] = 0;
+			return;
+		case IRQ_MAC_ADB:
+			oss->irq_level[OSS_IOPISM] = 0;
+			return;
+		case IRQ_MAC_SCSI:
+			oss->irq_level[OSS_SCSI] = 0;
+			return;
+		case IRQ_NUBUS_9:
+		case IRQ_NUBUS_A:
+		case IRQ_NUBUS_B:
+		case IRQ_NUBUS_C:
+		case IRQ_NUBUS_D:
+		case IRQ_NUBUS_E:
+			irq -= NUBUS_SOURCE_BASE;
+			oss->irq_level[irq] = 0;
+			return;
+	}
+
+	if (IRQ_SRC(irq) == 1)
+		via_irq_disable(irq);
+}