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, 490 insertions, 0 deletions

diff --git a/drivers/video/vgastate.c b/drivers/video/vgastate.c
new file mode 100644
index 000000000..6a29d198f
--- /dev/null
+++ b/drivers/video/vgastate.c
@@ -0,0 +1,490 @@
+/*
+ * linux/drivers/video/vgastate.c -- VGA state save/restore
+ *
+ * Copyright 2002 James Simmons
+ *
+ * Copyright history from vga16fb.c:
+ *	Copyright 1999 Ben Pfaff and Petr Vandrovec
+ *	Based on VGA info at http://www.goodnet.com/~tinara/FreeVGA/home.htm
+ *	Based on VESA framebuffer (c) 1998 Gerd Knorr
+ *
+ * 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/module.h>
+#include <linux/slab.h>
+#include <linux/fb.h>
+#include <linux/vmalloc.h>
+#include <video/vga.h>
+
+struct regstate {
+	__u8 *vga_font0;
+	__u8 *vga_font1;
+	__u8 *vga_text;
+	__u8 *vga_cmap;
+	__u8 *attr;
+	__u8 *crtc;
+	__u8 *gfx;
+	__u8 *seq;
+	__u8 misc;
+};
+
+static inline unsigned char vga_rcrtcs(void __iomem *regbase, unsigned short iobase,
+				       unsigned char reg)
+{
+	vga_w(regbase, iobase + 0x4, reg);
+	return vga_r(regbase, iobase + 0x5);
+}
+
+static inline void vga_wcrtcs(void __iomem *regbase, unsigned short iobase,
+			      unsigned char reg, unsigned char val)
+{
+	vga_w(regbase, iobase + 0x4, reg);
+	vga_w(regbase, iobase + 0x5, val);
+}
+
+static void save_vga_text(struct vgastate *state, void __iomem *fbbase)
+{
+	struct regstate *saved = (struct regstate *) state->vidstate;
+	int i;
+	u8 misc, attr10, gr4, gr5, gr6, seq1, seq2, seq4;
+	unsigned short iobase;
+
+	/* if in graphics mode, no need to save */
+	misc = vga_r(state->vgabase, VGA_MIS_R);
+	iobase = (misc & 1) ? 0x3d0 : 0x3b0;
+
+	vga_r(state->vgabase, iobase + 0xa);
+	vga_w(state->vgabase, VGA_ATT_W, 0x00);
+	attr10 = vga_rattr(state->vgabase, 0x10);
+	vga_r(state->vgabase, iobase + 0xa);
+	vga_w(state->vgabase, VGA_ATT_W, 0x20);
+
+	if (attr10 & 1)
+		return;
+
+	/* save regs */
+	gr4 = vga_rgfx(state->vgabase, VGA_GFX_PLANE_READ);
+	gr5 = vga_rgfx(state->vgabase, VGA_GFX_MODE);
+	gr6 = vga_rgfx(state->vgabase, VGA_GFX_MISC);
+	seq2 = vga_rseq(state->vgabase, VGA_SEQ_PLANE_WRITE);
+	seq4 = vga_rseq(state->vgabase, VGA_SEQ_MEMORY_MODE);
+
+	/* blank screen */
+	seq1 = vga_rseq(state->vgabase, VGA_SEQ_CLOCK_MODE);
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x1);
+	vga_wseq(state->vgabase, VGA_SEQ_CLOCK_MODE, seq1 | 1 << 5);
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x3);
+
+	/* save font at plane 2 */
+	if (state->flags & VGA_SAVE_FONT0) {
+		vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, 0x4);
+		vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, 0x6);
+		vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, 0x2);
+		vga_wgfx(state->vgabase, VGA_GFX_MODE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MISC, 0x5);
+		for (i = 0; i < 4 * 8192; i++)
+			saved->vga_font0[i] = vga_r(fbbase, i);
+	}
+
+	/* save font at plane 3 */
+	if (state->flags & VGA_SAVE_FONT1) {
+		vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, 0x8);
+		vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, 0x6);
+		vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, 0x3);
+		vga_wgfx(state->vgabase, VGA_GFX_MODE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MISC, 0x5);
+		for (i = 0; i < state->memsize; i++)
+			saved->vga_font1[i] = vga_r(fbbase, i);
+	}
+
+	/* save font at plane 0/1 */
+	if (state->flags & VGA_SAVE_TEXT) {
+		vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, 0x1);
+		vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, 0x6);
+		vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MODE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MISC, 0x5);
+		for (i = 0; i < 8192; i++)
+			saved->vga_text[i] = vga_r(fbbase, i);
+
+		vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, 0x2);
+		vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, 0x6);
+		vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, 0x1);
+		vga_wgfx(state->vgabase, VGA_GFX_MODE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MISC, 0x5);
+		for (i = 0; i < 8192; i++)
+			saved->vga_text[8192+i] = vga_r(fbbase + 2 * 8192, i);
+	}
+
+	/* restore regs */
+	vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, seq2);
+	vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, seq4);
+
+	vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, gr4);
+	vga_wgfx(state->vgabase, VGA_GFX_MODE, gr5);
+	vga_wgfx(state->vgabase, VGA_GFX_MISC, gr6);
+
+	/* unblank screen */
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x1);
+	vga_wseq(state->vgabase, VGA_SEQ_CLOCK_MODE, seq1 & ~(1 << 5));
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x3);
+
+	vga_wseq(state->vgabase, VGA_SEQ_CLOCK_MODE, seq1);
+}
+
+static void restore_vga_text(struct vgastate *state, void __iomem *fbbase)
+{
+	struct regstate *saved = (struct regstate *) state->vidstate;
+	int i;
+	u8 gr1, gr3, gr4, gr5, gr6, gr8;
+	u8 seq1, seq2, seq4;
+
+	/* save regs */
+	gr1 = vga_rgfx(state->vgabase, VGA_GFX_SR_ENABLE);
+	gr3 = vga_rgfx(state->vgabase, VGA_GFX_DATA_ROTATE);
+	gr4 = vga_rgfx(state->vgabase, VGA_GFX_PLANE_READ);
+	gr5 = vga_rgfx(state->vgabase, VGA_GFX_MODE);
+	gr6 = vga_rgfx(state->vgabase, VGA_GFX_MISC);
+	gr8 = vga_rgfx(state->vgabase, VGA_GFX_BIT_MASK);
+	seq2 = vga_rseq(state->vgabase, VGA_SEQ_PLANE_WRITE);
+	seq4 = vga_rseq(state->vgabase, VGA_SEQ_MEMORY_MODE);
+
+	/* blank screen */
+	seq1 = vga_rseq(state->vgabase, VGA_SEQ_CLOCK_MODE);
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x1);
+	vga_wseq(state->vgabase, VGA_SEQ_CLOCK_MODE, seq1 | 1 << 5);
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x3);
+
+	if (state->depth == 4) {
+		vga_wgfx(state->vgabase, VGA_GFX_DATA_ROTATE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_BIT_MASK, 0xff);
+		vga_wgfx(state->vgabase, VGA_GFX_SR_ENABLE, 0x00);
+	}
+
+	/* restore font at plane 2 */
+	if (state->flags & VGA_SAVE_FONT0) {
+		vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, 0x4);
+		vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, 0x6);
+		vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, 0x2);
+		vga_wgfx(state->vgabase, VGA_GFX_MODE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MISC, 0x5);
+		for (i = 0; i < 4 * 8192; i++)
+			vga_w(fbbase, i, saved->vga_font0[i]);
+	}
+
+	/* restore font at plane 3 */
+	if (state->flags & VGA_SAVE_FONT1) {
+		vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, 0x8);
+		vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, 0x6);
+		vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, 0x3);
+		vga_wgfx(state->vgabase, VGA_GFX_MODE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MISC, 0x5);
+		for (i = 0; i < state->memsize; i++)
+			vga_w(fbbase, i, saved->vga_font1[i]);
+	}
+
+	/* restore font at plane 0/1 */
+	if (state->flags & VGA_SAVE_TEXT) {
+		vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, 0x1);
+		vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, 0x6);
+		vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MODE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MISC, 0x5);
+		for (i = 0; i < 8192; i++)
+			vga_w(fbbase, i, saved->vga_text[i]);
+
+		vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, 0x2);
+		vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, 0x6);
+		vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, 0x1);
+		vga_wgfx(state->vgabase, VGA_GFX_MODE, 0x0);
+		vga_wgfx(state->vgabase, VGA_GFX_MISC, 0x5);
+		for (i = 0; i < 8192; i++)
+			vga_w(fbbase, i, saved->vga_text[8192+i]);
+	}
+
+	/* unblank screen */
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x1);
+	vga_wseq(state->vgabase, VGA_SEQ_CLOCK_MODE, seq1 & ~(1 << 5));
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x3);
+
+	/* restore regs */
+	vga_wgfx(state->vgabase, VGA_GFX_SR_ENABLE, gr1);
+	vga_wgfx(state->vgabase, VGA_GFX_DATA_ROTATE, gr3);
+	vga_wgfx(state->vgabase, VGA_GFX_PLANE_READ, gr4);
+	vga_wgfx(state->vgabase, VGA_GFX_MODE, gr5);
+	vga_wgfx(state->vgabase, VGA_GFX_MISC, gr6);
+	vga_wgfx(state->vgabase, VGA_GFX_BIT_MASK, gr8);
+
+	vga_wseq(state->vgabase, VGA_SEQ_CLOCK_MODE, seq1);
+	vga_wseq(state->vgabase, VGA_SEQ_PLANE_WRITE, seq2);
+	vga_wseq(state->vgabase, VGA_SEQ_MEMORY_MODE, seq4);
+}
+
+static void save_vga_mode(struct vgastate *state)
+{
+	struct regstate *saved = (struct regstate *) state->vidstate;
+	unsigned short iobase;
+	int i;
+
+	saved->misc = vga_r(state->vgabase, VGA_MIS_R);
+	if (saved->misc & 1)
+		iobase = 0x3d0;
+	else
+		iobase = 0x3b0;
+
+	for (i = 0; i < state->num_crtc; i++)
+		saved->crtc[i] = vga_rcrtcs(state->vgabase, iobase, i);
+
+	vga_r(state->vgabase, iobase + 0xa);
+	vga_w(state->vgabase, VGA_ATT_W, 0x00);
+	for (i = 0; i < state->num_attr; i++) {
+		vga_r(state->vgabase, iobase + 0xa);
+		saved->attr[i] = vga_rattr(state->vgabase, i);
+	}
+	vga_r(state->vgabase, iobase + 0xa);
+	vga_w(state->vgabase, VGA_ATT_W, 0x20);
+
+	for (i = 0; i < state->num_gfx; i++)
+		saved->gfx[i] = vga_rgfx(state->vgabase, i);
+
+	for (i = 0; i < state->num_seq; i++)
+		saved->seq[i] = vga_rseq(state->vgabase, i);
+}
+
+static void restore_vga_mode(struct vgastate *state)
+{
+	struct regstate *saved = (struct regstate *) state->vidstate;
+	unsigned short iobase;
+	int i;
+
+	vga_w(state->vgabase, VGA_MIS_W, saved->misc);
+
+	if (saved->misc & 1)
+		iobase = 0x3d0;
+	else
+		iobase = 0x3b0;
+
+	/* turn off display */
+	vga_wseq(state->vgabase, VGA_SEQ_CLOCK_MODE,
+		 saved->seq[VGA_SEQ_CLOCK_MODE] | 0x20);
+
+	/* disable sequencer */
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x01);
+
+	/* enable palette addressing */
+	vga_r(state->vgabase, iobase + 0xa);
+	vga_w(state->vgabase, VGA_ATT_W, 0x00);
+
+	for (i = 2; i < state->num_seq; i++)
+		vga_wseq(state->vgabase, i, saved->seq[i]);
+
+
+	/* unprotect vga regs */
+	vga_wcrtcs(state->vgabase, iobase, 17, saved->crtc[17] & ~0x80);
+	for (i = 0; i < state->num_crtc; i++)
+		vga_wcrtcs(state->vgabase, iobase, i, saved->crtc[i]);
+
+	for (i = 0; i < state->num_gfx; i++)
+		vga_wgfx(state->vgabase, i, saved->gfx[i]);
+
+	for (i = 0; i < state->num_attr; i++) {
+		vga_r(state->vgabase, iobase + 0xa);
+		vga_wattr(state->vgabase, i, saved->attr[i]);
+	}
+
+	/* reenable sequencer */
+	vga_wseq(state->vgabase, VGA_SEQ_RESET, 0x03);
+	/* turn display on */
+	vga_wseq(state->vgabase, VGA_SEQ_CLOCK_MODE,
+		 saved->seq[VGA_SEQ_CLOCK_MODE] & ~(1 << 5));
+
+	/* disable video/palette source */
+	vga_r(state->vgabase, iobase + 0xa);
+	vga_w(state->vgabase, VGA_ATT_W, 0x20);
+}
+
+static void save_vga_cmap(struct vgastate *state)
+{
+	struct regstate *saved = (struct regstate *) state->vidstate;
+	int i;
+
+	vga_w(state->vgabase, VGA_PEL_MSK, 0xff);
+
+	/* assumes DAC is readable and writable */
+	vga_w(state->vgabase, VGA_PEL_IR, 0x00);
+	for (i = 0; i < 768; i++)
+		saved->vga_cmap[i] = vga_r(state->vgabase, VGA_PEL_D);
+}
+
+static void restore_vga_cmap(struct vgastate *state)
+{
+	struct regstate *saved = (struct regstate *) state->vidstate;
+	int i;
+
+	vga_w(state->vgabase, VGA_PEL_MSK, 0xff);
+
+	/* assumes DAC is readable and writable */
+	vga_w(state->vgabase, VGA_PEL_IW, 0x00);
+	for (i = 0; i < 768; i++)
+		vga_w(state->vgabase, VGA_PEL_D, saved->vga_cmap[i]);
+}
+
+static void vga_cleanup(struct vgastate *state)
+{
+	if (state->vidstate != NULL) {
+		struct regstate *saved = (struct regstate *) state->vidstate;
+
+		vfree(saved->vga_font0);
+		vfree(saved->vga_font1);
+		vfree(saved->vga_text);
+		vfree(saved->vga_cmap);
+		vfree(saved->attr);
+		kfree(saved);
+		state->vidstate = NULL;
+	}
+}
+
+int save_vga(struct vgastate *state)
+{
+	struct regstate *saved;
+
+	saved = kzalloc_obj(struct regstate);
+
+	if (saved == NULL)
+		return 1;
+
+	state->vidstate = (void *)saved;
+
+	if (state->flags & VGA_SAVE_CMAP) {
+		saved->vga_cmap = vmalloc(768);
+		if (!saved->vga_cmap) {
+			vga_cleanup(state);
+			return 1;
+		}
+		save_vga_cmap(state);
+	}
+
+	if (state->flags & VGA_SAVE_MODE) {
+		int total;
+
+		if (state->num_attr < 21)
+			state->num_attr = 21;
+		if (state->num_crtc < 25)
+			state->num_crtc = 25;
+		if (state->num_gfx < 9)
+			state->num_gfx = 9;
+		if (state->num_seq < 5)
+			state->num_seq = 5;
+		total = state->num_attr + state->num_crtc +
+			state->num_gfx + state->num_seq;
+
+		saved->attr = vmalloc(total);
+		if (!saved->attr) {
+			vga_cleanup(state);
+			return 1;
+		}
+		saved->crtc = saved->attr + state->num_attr;
+		saved->gfx = saved->crtc + state->num_crtc;
+		saved->seq = saved->gfx + state->num_gfx;
+
+		save_vga_mode(state);
+	}
+
+	if (state->flags & VGA_SAVE_FONTS) {
+		void __iomem *fbbase;
+
+		/* exit if window is less than 32K */
+		if (state->memsize && state->memsize < 4 * 8192) {
+			vga_cleanup(state);
+			return 1;
+		}
+		if (!state->memsize)
+			state->memsize = 8 * 8192;
+
+		if (!state->membase)
+			state->membase = 0xA0000;
+
+		fbbase = ioremap(state->membase, state->memsize);
+
+		if (!fbbase) {
+			vga_cleanup(state);
+			return 1;
+		}
+
+		/*
+		 * save only first 32K used by vgacon
+		 */
+		if (state->flags & VGA_SAVE_FONT0) {
+			saved->vga_font0 = vmalloc(4 * 8192);
+			if (!saved->vga_font0) {
+				iounmap(fbbase);
+				vga_cleanup(state);
+				return 1;
+			}
+		}
+		/*
+		 * largely unused, but if required by the caller
+		 * we'll just save everything.
+		 */
+		if (state->flags & VGA_SAVE_FONT1) {
+			saved->vga_font1 = vmalloc(state->memsize);
+			if (!saved->vga_font1) {
+				iounmap(fbbase);
+				vga_cleanup(state);
+				return 1;
+			}
+		}
+		/*
+		 * Save 8K at plane0[0], and 8K at plane1[16K]
+		 */
+		if (state->flags & VGA_SAVE_TEXT) {
+			saved->vga_text = vmalloc(8192 * 2);
+			if (!saved->vga_text) {
+				iounmap(fbbase);
+				vga_cleanup(state);
+				return 1;
+			}
+		}
+
+		save_vga_text(state, fbbase);
+		iounmap(fbbase);
+	}
+	return 0;
+}
+
+int restore_vga(struct vgastate *state)
+{
+	if (state->vidstate == NULL)
+		return 1;
+
+	if (state->flags & VGA_SAVE_MODE)
+		restore_vga_mode(state);
+
+	if (state->flags & VGA_SAVE_FONTS) {
+		void __iomem *fbbase = ioremap(state->membase, state->memsize);
+
+		if (!fbbase) {
+			vga_cleanup(state);
+			return 1;
+		}
+		restore_vga_text(state, fbbase);
+		iounmap(fbbase);
+	}
+
+	if (state->flags & VGA_SAVE_CMAP)
+		restore_vga_cmap(state);
+
+	vga_cleanup(state);
+	return 0;
+}
+
+EXPORT_SYMBOL(save_vga);
+EXPORT_SYMBOL(restore_vga);
+
+MODULE_AUTHOR("James Simmons <jsimmons@users.sf.net>");
+MODULE_DESCRIPTION("VGA State Save/Restore");
+MODULE_LICENSE("GPL");
+