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, 259 insertions, 0 deletions

diff --git a/drivers/usb/dwc2/drd.c b/drivers/usb/dwc2/drd.c
new file mode 100644
index 000000000..1ad8fa3f8
--- /dev/null
+++ b/drivers/usb/dwc2/drd.c
@@ -0,0 +1,259 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * drd.c - DesignWare USB2 DRD Controller Dual-role support
+ *
+ * Copyright (C) 2020 STMicroelectronics
+ *
+ * Author(s): Amelie Delaunay <amelie.delaunay@st.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/iopoll.h>
+#include <linux/platform_device.h>
+#include <linux/usb/role.h>
+#include "core.h"
+
+#define dwc2_ovr_gotgctl(gotgctl) \
+	((gotgctl) |= GOTGCTL_BVALOEN | GOTGCTL_AVALOEN | GOTGCTL_VBVALOEN | \
+	 GOTGCTL_DBNCE_FLTR_BYPASS)
+
+static void dwc2_ovr_init(struct dwc2_hsotg *hsotg)
+{
+	unsigned long flags;
+	u32 gotgctl;
+
+	spin_lock_irqsave(&hsotg->lock, flags);
+
+	gotgctl = dwc2_readl(hsotg, GOTGCTL);
+	dwc2_ovr_gotgctl(gotgctl);
+	gotgctl &= ~(GOTGCTL_BVALOVAL | GOTGCTL_AVALOVAL | GOTGCTL_VBVALOVAL);
+	if (hsotg->role_sw_default_mode == USB_DR_MODE_HOST)
+		gotgctl |= GOTGCTL_AVALOVAL | GOTGCTL_VBVALOVAL;
+	else if (hsotg->role_sw_default_mode == USB_DR_MODE_PERIPHERAL)
+		gotgctl |= GOTGCTL_BVALOVAL | GOTGCTL_VBVALOVAL;
+	dwc2_writel(hsotg, gotgctl, GOTGCTL);
+
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+
+	dwc2_force_mode(hsotg, (hsotg->dr_mode == USB_DR_MODE_HOST) ||
+				(hsotg->role_sw_default_mode == USB_DR_MODE_HOST));
+}
+
+static int dwc2_ovr_avalid(struct dwc2_hsotg *hsotg, bool valid)
+{
+	u32 gotgctl = dwc2_readl(hsotg, GOTGCTL);
+
+	/* Check if A-Session is already in the right state */
+	if ((valid && (gotgctl & GOTGCTL_ASESVLD)) ||
+	    (!valid && !(gotgctl & GOTGCTL_ASESVLD)))
+		return -EALREADY;
+
+	/* Always enable overrides to handle the resume case */
+	dwc2_ovr_gotgctl(gotgctl);
+
+	gotgctl &= ~GOTGCTL_BVALOVAL;
+	if (valid)
+		gotgctl |= GOTGCTL_AVALOVAL | GOTGCTL_VBVALOVAL;
+	else
+		gotgctl &= ~(GOTGCTL_AVALOVAL | GOTGCTL_VBVALOVAL);
+	dwc2_writel(hsotg, gotgctl, GOTGCTL);
+
+	return 0;
+}
+
+static int dwc2_ovr_bvalid(struct dwc2_hsotg *hsotg, bool valid)
+{
+	u32 gotgctl = dwc2_readl(hsotg, GOTGCTL);
+
+	/* Check if B-Session is already in the right state */
+	if ((valid && (gotgctl & GOTGCTL_BSESVLD)) ||
+	    (!valid && !(gotgctl & GOTGCTL_BSESVLD)))
+		return -EALREADY;
+
+	/* Always enable overrides to handle the resume case */
+	dwc2_ovr_gotgctl(gotgctl);
+
+	gotgctl &= ~GOTGCTL_AVALOVAL;
+	if (valid)
+		gotgctl |= GOTGCTL_BVALOVAL | GOTGCTL_VBVALOVAL;
+	else
+		gotgctl &= ~(GOTGCTL_BVALOVAL | GOTGCTL_VBVALOVAL);
+	dwc2_writel(hsotg, gotgctl, GOTGCTL);
+
+	return 0;
+}
+
+static int dwc2_drd_role_sw_set(struct usb_role_switch *sw, enum usb_role role)
+{
+	struct dwc2_hsotg *hsotg = usb_role_switch_get_drvdata(sw);
+	unsigned long flags;
+	int already = 0;
+
+	/* Skip session not in line with dr_mode */
+	if ((role == USB_ROLE_DEVICE && hsotg->dr_mode == USB_DR_MODE_HOST) ||
+	    (role == USB_ROLE_HOST && hsotg->dr_mode == USB_DR_MODE_PERIPHERAL))
+		return -EINVAL;
+
+#if IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) || \
+	IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)
+	/* Skip session if core is in test mode */
+	if (role == USB_ROLE_NONE && hsotg->test_mode) {
+		dev_dbg(hsotg->dev, "Core is in test mode\n");
+		return -EBUSY;
+	}
+#endif
+
+	/*
+	 * In case of USB_DR_MODE_PERIPHERAL, clock is disabled at the end of
+	 * the probe and enabled on udc_start.
+	 * If role-switch set is called before the udc_start, we need to enable
+	 * the clock to read/write GOTGCTL and GUSBCFG registers to override
+	 * mode and sessions. It is the case if cable is plugged at boot.
+	 */
+	if (!hsotg->ll_hw_enabled && hsotg->clk) {
+		int ret = clk_prepare_enable(hsotg->clk);
+
+		if (ret)
+			return ret;
+	}
+
+	spin_lock_irqsave(&hsotg->lock, flags);
+
+	if (role == USB_ROLE_NONE) {
+		/* default operation mode when usb role is USB_ROLE_NONE */
+		if (hsotg->role_sw_default_mode == USB_DR_MODE_HOST)
+			role = USB_ROLE_HOST;
+		else if (hsotg->role_sw_default_mode == USB_DR_MODE_PERIPHERAL)
+			role = USB_ROLE_DEVICE;
+	}
+
+	if ((IS_ENABLED(CONFIG_USB_DWC2_PERIPHERAL) ||
+	     IS_ENABLED(CONFIG_USB_DWC2_DUAL_ROLE)) &&
+	     dwc2_is_device_mode(hsotg) &&
+	     hsotg->lx_state == DWC2_L2 &&
+	     hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_NONE &&
+	     hsotg->bus_suspended &&
+	     !hsotg->params.no_clock_gating)
+		dwc2_gadget_exit_clock_gating(hsotg, 0);
+
+	if (role == USB_ROLE_HOST) {
+		already = dwc2_ovr_avalid(hsotg, true);
+	} else if (role == USB_ROLE_DEVICE) {
+		already = dwc2_ovr_bvalid(hsotg, true);
+		if (dwc2_is_device_enabled(hsotg)) {
+			/* This clear DCTL.SFTDISCON bit */
+			dwc2_hsotg_core_connect(hsotg);
+		}
+	} else {
+		if (dwc2_is_device_mode(hsotg)) {
+			if (!dwc2_ovr_bvalid(hsotg, false))
+				/* This set DCTL.SFTDISCON bit */
+				dwc2_hsotg_core_disconnect(hsotg);
+		} else {
+			dwc2_ovr_avalid(hsotg, false);
+		}
+	}
+
+	spin_unlock_irqrestore(&hsotg->lock, flags);
+
+	if (!already && hsotg->dr_mode == USB_DR_MODE_OTG)
+		/* This will raise a Connector ID Status Change Interrupt */
+		dwc2_force_mode(hsotg, role == USB_ROLE_HOST);
+
+	if (!hsotg->ll_hw_enabled && hsotg->clk)
+		clk_disable_unprepare(hsotg->clk);
+
+	dev_dbg(hsotg->dev, "%s-session valid\n",
+		role == USB_ROLE_NONE ? "No" :
+		role == USB_ROLE_HOST ? "A" : "B");
+
+	return 0;
+}
+
+int dwc2_drd_init(struct dwc2_hsotg *hsotg)
+{
+	struct usb_role_switch_desc role_sw_desc = {0};
+	struct usb_role_switch *role_sw;
+	int ret;
+
+	if (!device_property_read_bool(hsotg->dev, "usb-role-switch"))
+		return 0;
+
+	hsotg->role_sw_default_mode = usb_get_role_switch_default_mode(hsotg->dev);
+	role_sw_desc.driver_data = hsotg;
+	role_sw_desc.fwnode = dev_fwnode(hsotg->dev);
+	role_sw_desc.set = dwc2_drd_role_sw_set;
+	role_sw_desc.allow_userspace_control = true;
+
+	role_sw = usb_role_switch_register(hsotg->dev, &role_sw_desc);
+	if (IS_ERR(role_sw)) {
+		ret = PTR_ERR(role_sw);
+		dev_err(hsotg->dev,
+			"failed to register role switch: %d\n", ret);
+		return ret;
+	}
+
+	hsotg->role_sw = role_sw;
+
+	/* Enable override and initialize values */
+	dwc2_ovr_init(hsotg);
+
+	return 0;
+}
+
+void dwc2_drd_suspend(struct dwc2_hsotg *hsotg)
+{
+	u32 gintsts, gintmsk;
+
+	if (hsotg->role_sw && !hsotg->params.external_id_pin_ctl) {
+		gintmsk = dwc2_readl(hsotg, GINTMSK);
+		gintmsk &= ~GINTSTS_CONIDSTSCHNG;
+		dwc2_writel(hsotg, gintmsk, GINTMSK);
+		gintsts = dwc2_readl(hsotg, GINTSTS);
+		dwc2_writel(hsotg, gintsts | GINTSTS_CONIDSTSCHNG, GINTSTS);
+	}
+}
+
+void dwc2_drd_resume(struct dwc2_hsotg *hsotg)
+{
+	u32 gintsts, gintmsk;
+	enum usb_role role;
+
+	if (hsotg->role_sw) {
+		/* get last known role (as the get ops isn't implemented by this driver) */
+		role = usb_role_switch_get_role(hsotg->role_sw);
+
+		if (role == USB_ROLE_NONE) {
+			if (hsotg->role_sw_default_mode == USB_DR_MODE_HOST)
+				role = USB_ROLE_HOST;
+			else if (hsotg->role_sw_default_mode == USB_DR_MODE_PERIPHERAL)
+				role = USB_ROLE_DEVICE;
+		}
+
+		/* restore last role that may have been lost */
+		if (role == USB_ROLE_HOST)
+			dwc2_ovr_avalid(hsotg, true);
+		else if (role == USB_ROLE_DEVICE)
+			dwc2_ovr_bvalid(hsotg, true);
+
+		dwc2_force_mode(hsotg, role == USB_ROLE_HOST);
+
+		dev_dbg(hsotg->dev, "resuming %s-session valid\n",
+			role == USB_ROLE_NONE ? "No" :
+			role == USB_ROLE_HOST ? "A" : "B");
+	}
+
+	if (hsotg->role_sw && !hsotg->params.external_id_pin_ctl) {
+		gintsts = dwc2_readl(hsotg, GINTSTS);
+		dwc2_writel(hsotg, gintsts | GINTSTS_CONIDSTSCHNG, GINTSTS);
+		gintmsk = dwc2_readl(hsotg, GINTMSK);
+		gintmsk |= GINTSTS_CONIDSTSCHNG;
+		dwc2_writel(hsotg, gintmsk, GINTMSK);
+	}
+}
+
+void dwc2_drd_exit(struct dwc2_hsotg *hsotg)
+{
+	if (hsotg->role_sw)
+		usb_role_switch_unregister(hsotg->role_sw);
+}