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, 197 insertions, 0 deletions

diff --git a/drivers/video/fbdev/sunxvr1000.c b/drivers/video/fbdev/sunxvr1000.c
new file mode 100644
index 000000000..a93b06614
--- /dev/null
+++ b/drivers/video/fbdev/sunxvr1000.c
@@ -0,0 +1,197 @@
+/* sunxvr1000.c: Sun XVR-1000 fb driver for sparc64 systems
+ *
+ * License: GPL
+ *
+ * Copyright (C) 2010 David S. Miller (davem@davemloft.net)
+ */
+
+#include <linux/kernel.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct gfb_info {
+	struct fb_info		*info;
+
+	char __iomem		*fb_base;
+	unsigned long		fb_base_phys;
+
+	struct device_node	*of_node;
+
+	unsigned int		width;
+	unsigned int		height;
+	unsigned int		depth;
+	unsigned int		fb_size;
+
+	u32			pseudo_palette[16];
+};
+
+static int gfb_get_props(struct gfb_info *gp)
+{
+	gp->width = of_getintprop_default(gp->of_node, "width", 0);
+	gp->height = of_getintprop_default(gp->of_node, "height", 0);
+	gp->depth = of_getintprop_default(gp->of_node, "depth", 32);
+
+	if (!gp->width || !gp->height) {
+		printk(KERN_ERR "gfb: Critical properties missing for %pOF\n",
+		       gp->of_node);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int gfb_setcolreg(unsigned regno,
+			 unsigned red, unsigned green, unsigned blue,
+			 unsigned transp, struct fb_info *info)
+{
+	u32 value;
+
+	if (regno < 16) {
+		red >>= 8;
+		green >>= 8;
+		blue >>= 8;
+
+		value = (blue << 16) | (green << 8) | red;
+		((u32 *)info->pseudo_palette)[regno] = value;
+	}
+
+	return 0;
+}
+
+static const struct fb_ops gfb_ops = {
+	.owner			= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_setcolreg		= gfb_setcolreg,
+};
+
+static int gfb_set_fbinfo(struct gfb_info *gp)
+{
+	struct fb_info *info = gp->info;
+	struct fb_var_screeninfo *var = &info->var;
+
+	info->fbops = &gfb_ops;
+	info->screen_base = gp->fb_base;
+	info->screen_size = gp->fb_size;
+
+	info->pseudo_palette = gp->pseudo_palette;
+
+	/* Fill fix common fields */
+	strscpy(info->fix.id, "gfb", sizeof(info->fix.id));
+        info->fix.smem_start = gp->fb_base_phys;
+        info->fix.smem_len = gp->fb_size;
+        info->fix.type = FB_TYPE_PACKED_PIXELS;
+	if (gp->depth == 32 || gp->depth == 24)
+		info->fix.visual = FB_VISUAL_TRUECOLOR;
+	else
+		info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
+
+	var->xres = gp->width;
+	var->yres = gp->height;
+	var->xres_virtual = var->xres;
+	var->yres_virtual = var->yres;
+	var->bits_per_pixel = gp->depth;
+
+	var->red.offset = 0;
+	var->red.length = 8;
+	var->green.offset = 8;
+	var->green.length = 8;
+	var->blue.offset = 16;
+	var->blue.length = 8;
+	var->transp.offset = 0;
+	var->transp.length = 0;
+
+	if (fb_alloc_cmap(&info->cmap, 256, 0)) {
+		printk(KERN_ERR "gfb: Cannot allocate color map.\n");
+		return -ENOMEM;
+	}
+
+        return 0;
+}
+
+static int gfb_probe(struct platform_device *op)
+{
+	struct device_node *dp = op->dev.of_node;
+	struct fb_info *info;
+	struct gfb_info *gp;
+	int err;
+
+	info = framebuffer_alloc(sizeof(struct gfb_info), &op->dev);
+	if (!info) {
+		err = -ENOMEM;
+		goto err_out;
+	}
+
+	gp = info->par;
+	gp->info = info;
+	gp->of_node = dp;
+
+	gp->fb_base_phys = op->resource[6].start;
+
+	err = gfb_get_props(gp);
+	if (err)
+		goto err_release_fb;
+
+	/* Framebuffer length is the same regardless of resolution. */
+	info->fix.line_length = 16384;
+	gp->fb_size = info->fix.line_length * gp->height;
+
+	gp->fb_base = of_ioremap(&op->resource[6], 0,
+				 gp->fb_size, "gfb fb");
+	if (!gp->fb_base) {
+		err = -ENOMEM;
+		goto err_release_fb;
+	}
+
+	err = gfb_set_fbinfo(gp);
+	if (err)
+		goto err_unmap_fb;
+
+	printk("gfb: Found device at %pOF\n", dp);
+
+	err = register_framebuffer(info);
+	if (err < 0) {
+		printk(KERN_ERR "gfb: Could not register framebuffer %pOF\n",
+		       dp);
+		goto err_unmap_fb;
+	}
+
+	dev_set_drvdata(&op->dev, info);
+
+	return 0;
+
+err_unmap_fb:
+	of_iounmap(&op->resource[6], gp->fb_base, gp->fb_size);
+
+err_release_fb:
+        framebuffer_release(info);
+
+err_out:
+	return err;
+}
+
+static const struct of_device_id gfb_match[] = {
+	{
+		.name = "SUNW,gfb",
+	},
+	{},
+};
+
+static struct platform_driver gfb_driver = {
+	.probe		= gfb_probe,
+	.driver = {
+		.name			= "gfb",
+		.of_match_table		= gfb_match,
+		.suppress_bind_attrs	= true,
+	},
+};
+
+static int __init gfb_init(void)
+{
+	if (fb_get_options("gfb", NULL))
+		return -ENODEV;
+
+	return platform_driver_register(&gfb_driver);
+}
+device_initcall(gfb_init);