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, 315 insertions, 0 deletions

diff --git a/drivers/scsi/a3000.c b/drivers/scsi/a3000.c
new file mode 100644
index 000000000..bf054dd76
--- /dev/null
+++ b/drivers/scsi/a3000.c
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/ioport.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
+#include <linux/module.h>
+
+#include <asm/page.h>
+#include <asm/amigaints.h>
+#include <asm/amigahw.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_tcq.h>
+#include "wd33c93.h"
+#include "a3000.h"
+
+
+struct a3000_hostdata {
+	struct WD33C93_hostdata wh;
+	struct a3000_scsiregs *regs;
+	struct device *dev;
+};
+
+#define DMA_DIR(d)   ((d == DATA_OUT_DIR) ? DMA_TO_DEVICE : DMA_FROM_DEVICE)
+
+static irqreturn_t a3000_intr(int irq, void *data)
+{
+	struct Scsi_Host *instance = data;
+	struct a3000_hostdata *hdata = shost_priv(instance);
+	unsigned int status = hdata->regs->ISTR;
+	unsigned long flags;
+
+	if (!(status & ISTR_INT_P))
+		return IRQ_NONE;
+	if (status & ISTR_INTS) {
+		spin_lock_irqsave(instance->host_lock, flags);
+		wd33c93_intr(instance);
+		spin_unlock_irqrestore(instance->host_lock, flags);
+		return IRQ_HANDLED;
+	}
+	pr_warn("Non-serviced A3000 SCSI-interrupt? ISTR = %02x\n", status);
+	return IRQ_NONE;
+}
+
+static int dma_setup(struct scsi_cmnd *cmd, int dir_in)
+{
+	struct scsi_pointer *scsi_pointer = WD33C93_scsi_pointer(cmd);
+	unsigned long len = scsi_pointer->this_residual;
+	struct Scsi_Host *instance = cmd->device->host;
+	struct a3000_hostdata *hdata = shost_priv(instance);
+	struct WD33C93_hostdata *wh = &hdata->wh;
+	struct a3000_scsiregs *regs = hdata->regs;
+	unsigned short cntr = CNTR_PDMD | CNTR_INTEN;
+	dma_addr_t addr;
+
+	addr = dma_map_single(hdata->dev, scsi_pointer->ptr,
+			      len, DMA_DIR(dir_in));
+	if (dma_mapping_error(hdata->dev, addr)) {
+		dev_warn(hdata->dev, "cannot map SCSI data block %p\n",
+			 scsi_pointer->ptr);
+		return 1;
+	}
+	scsi_pointer->dma_handle = addr;
+
+	/*
+	 * if the physical address has the wrong alignment, or if
+	 * physical address is bad, or if it is a write and at the
+	 * end of a physical memory chunk, then allocate a bounce
+	 * buffer
+	 * MSch 20220629 - only wrong alignment tested - bounce
+	 * buffer returned by kmalloc is guaranteed to be aligned
+	 */
+	if (addr & A3000_XFER_MASK) {
+		WARN_ONCE(1, "Invalid alignment for DMA!");
+		/* drop useless mapping */
+		dma_unmap_single(hdata->dev, scsi_pointer->dma_handle,
+				 scsi_pointer->this_residual,
+				 DMA_DIR(dir_in));
+
+		wh->dma_bounce_len = (scsi_pointer->this_residual + 511) & ~0x1ff;
+		wh->dma_bounce_buffer = kmalloc(wh->dma_bounce_len,
+						GFP_KERNEL);
+
+		/* can't allocate memory; use PIO */
+		if (!wh->dma_bounce_buffer) {
+			wh->dma_bounce_len = 0;
+			scsi_pointer->dma_handle = (dma_addr_t) NULL;
+			return 1;
+		}
+
+		if (!dir_in) {
+			/* copy to bounce buffer for a write */
+			memcpy(wh->dma_bounce_buffer, scsi_pointer->ptr,
+			       scsi_pointer->this_residual);
+		}
+
+		addr = dma_map_single(hdata->dev, scsi_pointer->ptr,
+				      len, DMA_DIR(dir_in));
+		if (dma_mapping_error(hdata->dev, addr)) {
+			dev_warn(hdata->dev,
+				 "cannot map SCSI data block %p\n",
+				 scsi_pointer->ptr);
+			return 1;
+		}
+		scsi_pointer->dma_handle = addr;
+	}
+
+	/* setup dma direction */
+	if (!dir_in)
+		cntr |= CNTR_DDIR;
+
+	/* remember direction */
+	wh->dma_dir = dir_in;
+
+	regs->CNTR = cntr;
+
+	/* setup DMA *physical* address */
+	regs->ACR = addr;
+
+	/* no more cache flush here - dma_map_single() takes care */
+
+	/* start DMA */
+	mb();			/* make sure setup is completed */
+	regs->ST_DMA = 1;
+	mb();			/* make sure DMA has started before next IO */
+
+	/* return success */
+	return 0;
+}
+
+static void dma_stop(struct Scsi_Host *instance, struct scsi_cmnd *SCpnt,
+		     int status)
+{
+	struct scsi_pointer *scsi_pointer = WD33C93_scsi_pointer(SCpnt);
+	struct a3000_hostdata *hdata = shost_priv(instance);
+	struct WD33C93_hostdata *wh = &hdata->wh;
+	struct a3000_scsiregs *regs = hdata->regs;
+
+	/* disable SCSI interrupts */
+	unsigned short cntr = CNTR_PDMD;
+
+	if (!wh->dma_dir)
+		cntr |= CNTR_DDIR;
+
+	regs->CNTR = cntr;
+	mb();			/* make sure CNTR is updated before next IO */
+
+	/* flush if we were reading */
+	if (wh->dma_dir) {
+		regs->FLUSH = 1;
+		mb();		/* don't allow prefetch */
+		while (!(regs->ISTR & ISTR_FE_FLG))
+			barrier();
+		mb();		/* no IO until FLUSH is done */
+	}
+
+	/* clear a possible interrupt */
+	/* I think that this CINT is only necessary if you are
+	 * using the terminal count features.   HM 7 Mar 1994
+	 */
+	regs->CINT = 1;
+
+	/* stop DMA */
+	regs->SP_DMA = 1;
+	mb();			/* make sure DMA is stopped before next IO */
+
+	/* restore the CONTROL bits (minus the direction flag) */
+	regs->CNTR = CNTR_PDMD | CNTR_INTEN;
+	mb();			/* make sure CNTR is updated before next IO */
+
+	dma_unmap_single(hdata->dev, scsi_pointer->dma_handle,
+			 scsi_pointer->this_residual,
+			 DMA_DIR(wh->dma_dir));
+
+	/* copy from a bounce buffer, if necessary */
+	if (status && wh->dma_bounce_buffer) {
+		if (SCpnt) {
+			if (wh->dma_dir && SCpnt)
+				memcpy(scsi_pointer->ptr, wh->dma_bounce_buffer,
+				       scsi_pointer->this_residual);
+			kfree(wh->dma_bounce_buffer);
+			wh->dma_bounce_buffer = NULL;
+			wh->dma_bounce_len = 0;
+		} else {
+			kfree(wh->dma_bounce_buffer);
+			wh->dma_bounce_buffer = NULL;
+			wh->dma_bounce_len = 0;
+		}
+	}
+}
+
+static const struct scsi_host_template amiga_a3000_scsi_template = {
+	.module			= THIS_MODULE,
+	.name			= "Amiga 3000 built-in SCSI",
+	.show_info		= wd33c93_show_info,
+	.write_info		= wd33c93_write_info,
+	.proc_name		= "A3000",
+	.queuecommand		= wd33c93_queuecommand,
+	.eh_abort_handler	= wd33c93_abort,
+	.eh_host_reset_handler	= wd33c93_host_reset,
+	.can_queue		= CAN_QUEUE,
+	.this_id		= 7,
+	.sg_tablesize		= SG_ALL,
+	.cmd_per_lun		= CMD_PER_LUN,
+	.cmd_size		= sizeof(struct scsi_pointer),
+};
+
+static int __init amiga_a3000_scsi_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct Scsi_Host *instance;
+	int error;
+	struct a3000_scsiregs *regs;
+	wd33c93_regs wdregs;
+	struct a3000_hostdata *hdata;
+
+	if (dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32))) {
+		dev_warn(&pdev->dev, "cannot use 32 bit DMA\n");
+		return -ENODEV;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	if (!request_mem_region(res->start, resource_size(res), "wd33c93"))
+		return -EBUSY;
+
+	instance = scsi_host_alloc(&amiga_a3000_scsi_template,
+				   sizeof(struct a3000_hostdata));
+	if (!instance) {
+		error = -ENOMEM;
+		goto fail_alloc;
+	}
+
+	instance->irq = IRQ_AMIGA_PORTS;
+
+	regs = ZTWO_VADDR(res->start);
+	regs->DAWR = DAWR_A3000;
+
+	wdregs.SASR = &regs->SASR;
+	wdregs.SCMD = &regs->SCMD;
+
+	hdata = shost_priv(instance);
+	hdata->dev = &pdev->dev;
+	hdata->wh.no_sync = 0xff;
+	hdata->wh.fast = 0;
+	hdata->wh.dma_mode = CTRL_DMA;
+	hdata->regs = regs;
+
+	wd33c93_init(instance, wdregs, dma_setup, dma_stop, WD33C93_FS_12_15);
+	error = request_irq(IRQ_AMIGA_PORTS, a3000_intr, IRQF_SHARED,
+			    "A3000 SCSI", instance);
+	if (error)
+		goto fail_irq;
+
+	regs->CNTR = CNTR_PDMD | CNTR_INTEN;
+
+	error = scsi_add_host(instance, NULL);
+	if (error)
+		goto fail_host;
+
+	platform_set_drvdata(pdev, instance);
+
+	scsi_scan_host(instance);
+	return 0;
+
+fail_host:
+	free_irq(IRQ_AMIGA_PORTS, instance);
+fail_irq:
+	scsi_host_put(instance);
+fail_alloc:
+	release_mem_region(res->start, resource_size(res));
+	return error;
+}
+
+static void __exit amiga_a3000_scsi_remove(struct platform_device *pdev)
+{
+	struct Scsi_Host *instance = platform_get_drvdata(pdev);
+	struct a3000_hostdata *hdata = shost_priv(instance);
+	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+	hdata->regs->CNTR = 0;
+	scsi_remove_host(instance);
+	free_irq(IRQ_AMIGA_PORTS, instance);
+	scsi_host_put(instance);
+	release_mem_region(res->start, resource_size(res));
+}
+
+/*
+ * amiga_a3000_scsi_remove() lives in .exit.text. For drivers registered via
+ * module_platform_driver_probe() this is ok because they cannot get unbound at
+ * runtime. So mark the driver struct with __refdata to prevent modpost
+ * triggering a section mismatch warning.
+ */
+static struct platform_driver amiga_a3000_scsi_driver __refdata = {
+	.remove = __exit_p(amiga_a3000_scsi_remove),
+	.driver = {
+		.name = "amiga-a3000-scsi",
+	},
+};
+
+module_platform_driver_probe(amiga_a3000_scsi_driver, amiga_a3000_scsi_probe);
+
+MODULE_DESCRIPTION("Amiga 3000 built-in SCSI");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:amiga-a3000-scsi");