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, 100 insertions, 0 deletions

diff --git a/arch/m68k/sun3/sun3ints.c b/arch/m68k/sun3/sun3ints.c
new file mode 100644
index 000000000..32eaf55f8
--- /dev/null
+++ b/arch/m68k/sun3/sun3ints.c
@@ -0,0 +1,100 @@
+ /*
+ * linux/arch/m68k/sun3/sun3ints.c -- Sun-3(x) Linux interrupt handling code
+ *
+ * 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.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/kernel_stat.h>
+#include <linux/interrupt.h>
+#include <asm/intersil.h>
+#include <asm/oplib.h>
+#include <asm/sun3ints.h>
+#include <asm/irq_regs.h>
+#include <linux/seq_file.h>
+
+#include "sun3.h"
+
+void sun3_disable_interrupts(void)
+{
+	sun3_disable_irq(0);
+}
+
+void sun3_enable_interrupts(void)
+{
+	sun3_enable_irq(0);
+}
+
+static unsigned char led_pattern[8] = {
+	(u8)~(0x80), (u8)~(0x01),
+	(u8)~(0x40), (u8)~(0x02),
+	(u8)~(0x20), (u8)~(0x04),
+	(u8)~(0x10), (u8)~(0x08)
+};
+
+volatile unsigned char* sun3_intreg;
+
+void sun3_enable_irq(unsigned int irq)
+{
+	*sun3_intreg |=  (1 << irq);
+}
+
+void sun3_disable_irq(unsigned int irq)
+{
+	*sun3_intreg &= ~(1 << irq);
+}
+
+static irqreturn_t sun3_int7(int irq, void *dev_id)
+{
+	unsigned int cnt;
+
+	cnt = kstat_irqs_cpu(irq, 0);
+	if (!(cnt % 2000))
+		sun3_leds(led_pattern[cnt % 16000 / 2000]);
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t sun3_int5(int irq, void *dev_id)
+{
+	unsigned long flags;
+	unsigned int cnt;
+
+	local_irq_save(flags);
+#ifdef CONFIG_SUN3
+	intersil_clear();
+#endif
+	sun3_disable_irq(5);
+	sun3_enable_irq(5);
+#ifdef CONFIG_SUN3
+	intersil_clear();
+#endif
+	legacy_timer_tick(1);
+	cnt = kstat_irqs_cpu(irq, 0);
+	if (!(cnt % 20))
+		sun3_leds(led_pattern[cnt % 160 / 20]);
+	local_irq_restore(flags);
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t sun3_vec255(int irq, void *dev_id)
+{
+	return IRQ_HANDLED;
+}
+
+void __init sun3_init_IRQ(void)
+{
+	*sun3_intreg = 1;
+
+	m68k_setup_user_interrupt(VEC_USER, 128);
+
+	if (request_irq(IRQ_AUTO_5, sun3_int5, 0, "clock", NULL))
+		pr_err("Couldn't register %s interrupt\n", "int5");
+	if (request_irq(IRQ_AUTO_7, sun3_int7, 0, "nmi", NULL))
+		pr_err("Couldn't register %s interrupt\n", "int7");
+	if (request_irq(IRQ_USER+127, sun3_vec255, 0, "vec255", NULL))
+		pr_err("Couldn't register %s interrupt\n", "vec255");
+}