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, 94 insertions, 0 deletions

diff --git a/drivers/fpga/xilinx-selectmap.c b/drivers/fpga/xilinx-selectmap.c
new file mode 100644
index 000000000..d0cbb5fdf
--- /dev/null
+++ b/drivers/fpga/xilinx-selectmap.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Xilinx Spartan6 and 7 Series SelectMAP interface driver
+ *
+ * (C) 2024 Charles Perry <charles.perry@savoirfairelinux.com>
+ *
+ * Manage Xilinx FPGA firmware loaded over the SelectMAP configuration
+ * interface.
+ */
+
+#include "xilinx-core.h"
+
+#include <linux/gpio/consumer.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct xilinx_selectmap_conf {
+	struct xilinx_fpga_core core;
+	void __iomem *base;
+};
+
+#define to_xilinx_selectmap_conf(obj) \
+	container_of(obj, struct xilinx_selectmap_conf, core)
+
+static int xilinx_selectmap_write(struct xilinx_fpga_core *core,
+				  const char *buf, size_t count)
+{
+	struct xilinx_selectmap_conf *conf = to_xilinx_selectmap_conf(core);
+	size_t i;
+
+	for (i = 0; i < count; ++i)
+		writeb(buf[i], conf->base);
+
+	return 0;
+}
+
+static int xilinx_selectmap_probe(struct platform_device *pdev)
+{
+	struct xilinx_selectmap_conf *conf;
+	struct gpio_desc *gpio;
+	void __iomem *base;
+
+	conf = devm_kzalloc(&pdev->dev, sizeof(*conf), GFP_KERNEL);
+	if (!conf)
+		return -ENOMEM;
+
+	conf->core.dev = &pdev->dev;
+	conf->core.write = xilinx_selectmap_write;
+
+	base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(base))
+		return dev_err_probe(&pdev->dev, PTR_ERR(base),
+				     "ioremap error\n");
+	conf->base = base;
+
+	/* CSI_B is active low */
+	gpio = devm_gpiod_get_optional(&pdev->dev, "csi", GPIOD_OUT_HIGH);
+	if (IS_ERR(gpio))
+		return dev_err_probe(&pdev->dev, PTR_ERR(gpio),
+				     "Failed to get CSI_B gpio\n");
+
+	/* RDWR_B is active low */
+	gpio = devm_gpiod_get_optional(&pdev->dev, "rdwr", GPIOD_OUT_HIGH);
+	if (IS_ERR(gpio))
+		return dev_err_probe(&pdev->dev, PTR_ERR(gpio),
+				     "Failed to get RDWR_B gpio\n");
+
+	return xilinx_core_probe(&conf->core);
+}
+
+static const struct of_device_id xlnx_selectmap_of_match[] = {
+	{ .compatible = "xlnx,fpga-xc7s-selectmap", }, // Spartan-7
+	{ .compatible = "xlnx,fpga-xc7a-selectmap", }, // Artix-7
+	{ .compatible = "xlnx,fpga-xc7k-selectmap", }, // Kintex-7
+	{ .compatible = "xlnx,fpga-xc7v-selectmap", }, // Virtex-7
+	{},
+};
+MODULE_DEVICE_TABLE(of, xlnx_selectmap_of_match);
+
+static struct platform_driver xilinx_selectmap_driver = {
+	.driver = {
+		.name = "xilinx-selectmap",
+		.of_match_table = xlnx_selectmap_of_match,
+	},
+	.probe  = xilinx_selectmap_probe,
+};
+
+module_platform_driver(xilinx_selectmap_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Charles Perry <charles.perry@savoirfairelinux.com>");
+MODULE_DESCRIPTION("Load Xilinx FPGA firmware over SelectMap");