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, 209 insertions, 0 deletions

diff --git a/drivers/scsi/jazz_esp.c b/drivers/scsi/jazz_esp.c
new file mode 100644
index 000000000..35137f5cf
--- /dev/null
+++ b/drivers/scsi/jazz_esp.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* jazz_esp.c: ESP front-end for MIPS JAZZ systems.
+ *
+ * Copyright (C) 2007 Thomas Bogendörfer (tsbogend@alpha.frankende)
+ */
+
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
+
+#include <asm/irq.h>
+#include <asm/io.h>
+#include <asm/dma.h>
+
+#include <asm/jazz.h>
+#include <asm/jazzdma.h>
+
+#include <scsi/scsi_host.h>
+
+#include "esp_scsi.h"
+
+#define DRV_MODULE_NAME		"jazz_esp"
+#define PFX DRV_MODULE_NAME	": "
+#define DRV_VERSION		"1.000"
+#define DRV_MODULE_RELDATE	"May 19, 2007"
+
+static void jazz_esp_write8(struct esp *esp, u8 val, unsigned long reg)
+{
+	*(volatile u8 *)(esp->regs + reg) = val;
+}
+
+static u8 jazz_esp_read8(struct esp *esp, unsigned long reg)
+{
+	return *(volatile u8 *)(esp->regs + reg);
+}
+
+static int jazz_esp_irq_pending(struct esp *esp)
+{
+	if (jazz_esp_read8(esp, ESP_STATUS) & ESP_STAT_INTR)
+		return 1;
+	return 0;
+}
+
+static void jazz_esp_reset_dma(struct esp *esp)
+{
+	vdma_disable ((int)esp->dma_regs);
+}
+
+static void jazz_esp_dma_drain(struct esp *esp)
+{
+	/* nothing to do */
+}
+
+static void jazz_esp_dma_invalidate(struct esp *esp)
+{
+	vdma_disable ((int)esp->dma_regs);
+}
+
+static void jazz_esp_send_dma_cmd(struct esp *esp, u32 addr, u32 esp_count,
+				  u32 dma_count, int write, u8 cmd)
+{
+	BUG_ON(!(cmd & ESP_CMD_DMA));
+
+	jazz_esp_write8(esp, (esp_count >> 0) & 0xff, ESP_TCLOW);
+	jazz_esp_write8(esp, (esp_count >> 8) & 0xff, ESP_TCMED);
+	vdma_disable ((int)esp->dma_regs);
+	if (write)
+		vdma_set_mode ((int)esp->dma_regs, DMA_MODE_READ);
+	else
+		vdma_set_mode ((int)esp->dma_regs, DMA_MODE_WRITE);
+
+	vdma_set_addr ((int)esp->dma_regs, addr);
+	vdma_set_count ((int)esp->dma_regs, dma_count);
+	vdma_enable ((int)esp->dma_regs);
+
+	scsi_esp_cmd(esp, cmd);
+}
+
+static int jazz_esp_dma_error(struct esp *esp)
+{
+	u32 enable = vdma_get_enable((int)esp->dma_regs);
+
+	if (enable & (R4030_MEM_INTR|R4030_ADDR_INTR))
+		return 1;
+
+	return 0;
+}
+
+static const struct esp_driver_ops jazz_esp_ops = {
+	.esp_write8	=	jazz_esp_write8,
+	.esp_read8	=	jazz_esp_read8,
+	.irq_pending	=	jazz_esp_irq_pending,
+	.reset_dma	=	jazz_esp_reset_dma,
+	.dma_drain	=	jazz_esp_dma_drain,
+	.dma_invalidate	=	jazz_esp_dma_invalidate,
+	.send_dma_cmd	=	jazz_esp_send_dma_cmd,
+	.dma_error	=	jazz_esp_dma_error,
+};
+
+static int esp_jazz_probe(struct platform_device *dev)
+{
+	const struct scsi_host_template *tpnt = &scsi_esp_template;
+	struct Scsi_Host *host;
+	struct esp *esp;
+	struct resource *res;
+	int err;
+
+	host = scsi_host_alloc(tpnt, sizeof(struct esp));
+
+	err = -ENOMEM;
+	if (!host)
+		goto fail;
+
+	host->max_id = 8;
+	esp = shost_priv(host);
+
+	esp->host = host;
+	esp->dev = &dev->dev;
+	esp->ops = &jazz_esp_ops;
+
+	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
+	if (!res)
+		goto fail_unlink;
+
+	esp->regs = (void __iomem *)res->start;
+	if (!esp->regs)
+		goto fail_unlink;
+
+	res = platform_get_resource(dev, IORESOURCE_MEM, 1);
+	if (!res)
+		goto fail_unlink;
+
+	esp->dma_regs = (void __iomem *)res->start;
+
+	esp->command_block = dma_alloc_coherent(esp->dev, 16,
+						&esp->command_block_dma,
+						GFP_KERNEL);
+	if (!esp->command_block)
+		goto fail_unmap_regs;
+
+	host->irq = err = platform_get_irq(dev, 0);
+	if (err < 0)
+		goto fail_unmap_command_block;
+	err = request_irq(host->irq, scsi_esp_intr, IRQF_SHARED, "ESP", esp);
+	if (err < 0)
+		goto fail_unmap_command_block;
+
+	esp->scsi_id = 7;
+	esp->host->this_id = esp->scsi_id;
+	esp->scsi_id_mask = (1 << esp->scsi_id);
+	esp->cfreq = 40000000;
+
+	dev_set_drvdata(&dev->dev, esp);
+
+	err = scsi_esp_register(esp);
+	if (err)
+		goto fail_free_irq;
+
+	return 0;
+
+fail_free_irq:
+	free_irq(host->irq, esp);
+fail_unmap_command_block:
+	dma_free_coherent(esp->dev, 16,
+			  esp->command_block,
+			  esp->command_block_dma);
+fail_unmap_regs:
+fail_unlink:
+	scsi_host_put(host);
+fail:
+	return err;
+}
+
+static void esp_jazz_remove(struct platform_device *dev)
+{
+	struct esp *esp = dev_get_drvdata(&dev->dev);
+	unsigned int irq = esp->host->irq;
+
+	scsi_esp_unregister(esp);
+
+	free_irq(irq, esp);
+	dma_free_coherent(esp->dev, 16,
+			  esp->command_block,
+			  esp->command_block_dma);
+
+	scsi_host_put(esp->host);
+}
+
+/* work with hotplug and coldplug */
+MODULE_ALIAS("platform:jazz_esp");
+
+static struct platform_driver esp_jazz_driver = {
+	.probe		= esp_jazz_probe,
+	.remove		= esp_jazz_remove,
+	.driver	= {
+		.name	= "jazz_esp",
+	},
+};
+module_platform_driver(esp_jazz_driver);
+
+MODULE_DESCRIPTION("JAZZ ESP SCSI driver");
+MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(DRV_VERSION);