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, 90 insertions, 0 deletions

diff --git a/drivers/firmware/imx/rm.c b/drivers/firmware/imx/rm.c
new file mode 100644
index 000000000..d492b99e1
--- /dev/null
+++ b/drivers/firmware/imx/rm.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2020 NXP
+ *
+ * File containing client-side RPC functions for the RM service. These
+ * function are ported to clients that communicate to the SC.
+ */
+
+#include <linux/firmware/imx/svc/rm.h>
+
+struct imx_sc_msg_rm_rsrc_owned {
+	struct imx_sc_rpc_msg hdr;
+	u16 resource;
+} __packed __aligned(4);
+
+/*
+ * This function check @resource is owned by current partition or not
+ *
+ * @param[in]     ipc         IPC handle
+ * @param[in]     resource    resource the control is associated with
+ *
+ * @return Returns 0 for not owned and 1 for owned.
+ */
+bool imx_sc_rm_is_resource_owned(struct imx_sc_ipc *ipc, u16 resource)
+{
+	struct imx_sc_msg_rm_rsrc_owned msg;
+	struct imx_sc_rpc_msg *hdr = &msg.hdr;
+
+	hdr->ver = IMX_SC_RPC_VERSION;
+	hdr->svc = IMX_SC_RPC_SVC_RM;
+	hdr->func = IMX_SC_RM_FUNC_IS_RESOURCE_OWNED;
+	hdr->size = 2;
+
+	msg.resource = resource;
+
+	/*
+	 * SCU firmware only returns value 0 or 1
+	 * for resource owned check which means not owned or owned.
+	 * So it is always successful.
+	 */
+	imx_scu_call_rpc(ipc, &msg, true);
+
+	return hdr->func;
+}
+EXPORT_SYMBOL(imx_sc_rm_is_resource_owned);
+
+struct imx_sc_msg_rm_get_resource_owner {
+	struct imx_sc_rpc_msg hdr;
+	union {
+		struct {
+			u16 resource;
+		} req;
+		struct {
+			u8 val;
+		} resp;
+	} data;
+} __packed __aligned(4);
+
+/*
+ * This function get @resource partition number
+ *
+ * @param[in]     ipc         IPC handle
+ * @param[in]     resource    resource the control is associated with
+ * @param[out]    pt          pointer to return the partition number
+ *
+ * @return Returns 0 for success and < 0 for errors.
+ */
+int imx_sc_rm_get_resource_owner(struct imx_sc_ipc *ipc, u16 resource, u8 *pt)
+{
+	struct imx_sc_msg_rm_get_resource_owner msg;
+	struct imx_sc_rpc_msg *hdr = &msg.hdr;
+	int ret;
+
+	hdr->ver = IMX_SC_RPC_VERSION;
+	hdr->svc = IMX_SC_RPC_SVC_RM;
+	hdr->func = IMX_SC_RM_FUNC_GET_RESOURCE_OWNER;
+	hdr->size = 2;
+
+	msg.data.req.resource = resource;
+
+	ret = imx_scu_call_rpc(ipc, &msg, true);
+	if (ret)
+		return ret;
+
+	if (pt)
+		*pt = msg.data.resp.val;
+
+	return 0;
+}
+EXPORT_SYMBOL(imx_sc_rm_get_resource_owner);