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, 145 insertions, 0 deletions

diff --git a/arch/mips/bcm63xx/cs.c b/arch/mips/bcm63xx/cs.c
new file mode 100644
index 000000000..29205badc
--- /dev/null
+++ b/arch/mips/bcm63xx/cs.c
@@ -0,0 +1,145 @@
+/*
+ * 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) 2008 Maxime Bizon <mbizon@freebox.fr>
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/spinlock.h>
+#include <linux/log2.h>
+#include <bcm63xx_cpu.h>
+#include <bcm63xx_io.h>
+#include <bcm63xx_regs.h>
+#include <bcm63xx_cs.h>
+
+static DEFINE_SPINLOCK(bcm63xx_cs_lock);
+
+/*
+ * check if given chip select exists
+ */
+static int is_valid_cs(unsigned int cs)
+{
+	if (cs > 6)
+		return 0;
+	return 1;
+}
+
+/*
+ * Configure chipselect base address and size (bytes).
+ * Size must be a power of two between 8k and 256M.
+ */
+int bcm63xx_set_cs_base(unsigned int cs, u32 base, unsigned int size)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	/* sanity check on size */
+	if (size != roundup_pow_of_two(size))
+		return -EINVAL;
+
+	if (size < 8 * 1024 || size > 256 * 1024 * 1024)
+		return -EINVAL;
+
+	val = (base & MPI_CSBASE_BASE_MASK);
+	/* 8k => 0 - 256M => 15 */
+	val |= (ilog2(size) - ilog2(8 * 1024)) << MPI_CSBASE_SIZE_SHIFT;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	bcm_mpi_writel(val, MPI_CSBASE_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_base);
+
+/*
+ * configure chipselect timing (ns)
+ */
+int bcm63xx_set_cs_timing(unsigned int cs, unsigned int wait,
+			   unsigned int setup, unsigned int hold)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	val &= ~(MPI_CSCTL_WAIT_MASK);
+	val &= ~(MPI_CSCTL_SETUP_MASK);
+	val &= ~(MPI_CSCTL_HOLD_MASK);
+	val |= wait << MPI_CSCTL_WAIT_SHIFT;
+	val |= setup << MPI_CSCTL_SETUP_SHIFT;
+	val |= hold << MPI_CSCTL_HOLD_SHIFT;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_timing);
+
+/*
+ * configure other chipselect parameter (data bus size, ...)
+ */
+int bcm63xx_set_cs_param(unsigned int cs, u32 params)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	/* none of this fields apply to pcmcia */
+	if (cs == MPI_CS_PCMCIA_COMMON ||
+	    cs == MPI_CS_PCMCIA_ATTR ||
+	    cs == MPI_CS_PCMCIA_IO)
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	val &= ~(MPI_CSCTL_DATA16_MASK);
+	val &= ~(MPI_CSCTL_SYNCMODE_MASK);
+	val &= ~(MPI_CSCTL_TSIZE_MASK);
+	val &= ~(MPI_CSCTL_ENDIANSWAP_MASK);
+	val |= params;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_param);
+
+/*
+ * set cs status (enable/disable)
+ */
+int bcm63xx_set_cs_status(unsigned int cs, int enable)
+{
+	unsigned long flags;
+	u32 val;
+
+	if (!is_valid_cs(cs))
+		return -EINVAL;
+
+	spin_lock_irqsave(&bcm63xx_cs_lock, flags);
+	val = bcm_mpi_readl(MPI_CSCTL_REG(cs));
+	if (enable)
+		val |= MPI_CSCTL_ENABLE_MASK;
+	else
+		val &= ~MPI_CSCTL_ENABLE_MASK;
+	bcm_mpi_writel(val, MPI_CSCTL_REG(cs));
+	spin_unlock_irqrestore(&bcm63xx_cs_lock, flags);
+	return 0;
+}
+
+EXPORT_SYMBOL(bcm63xx_set_cs_status);