From 02a1fbc3121aa47f5397c8f0db0d3c5ad0d78467 Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw@amazon.co.uk>
Date: Tue, 10 Jan 2023 01:09:04 +0000
Subject: [PATCH] hw/xen: Implement soft reset for emulated gnttab

This is only part of it; we will also need to get the PV back end drivers
to tear down their own mappings (or do it for them, but they kind of need
to stop using the pointers too).

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 hw/i386/kvm/xen_gnttab.c  | 26 ++++++++++++++++++++++++--
 hw/i386/kvm/xen_gnttab.h  |  1 +
 target/i386/kvm/xen-emu.c |  5 +++++
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/hw/i386/kvm/xen_gnttab.c b/hw/i386/kvm/xen_gnttab.c
index 8008a391bd..3fe3a8043b 100644
--- a/hw/i386/kvm/xen_gnttab.c
+++ b/hw/i386/kvm/xen_gnttab.c
@@ -72,13 +72,11 @@ static void xen_gnttab_realize(DeviceState *dev, Error **errp)
         error_setg(errp, "Xen grant table support is for Xen emulation");
         return;
     }
-    s->nr_frames = 0;
     s->max_frames = kvm_xen_get_gnttab_max_frames();
     memory_region_init_ram(&s->gnt_frames, OBJECT(dev), "xen:grant_table",
                            XEN_PAGE_SIZE * s->max_frames, &error_abort);
     memory_region_set_enabled(&s->gnt_frames, true);
     s->entries.v1 = memory_region_get_ram_ptr(&s->gnt_frames);
-    memset(s->entries.v1, 0, XEN_PAGE_SIZE * s->max_frames);
 
     /* Create individual page-sizes aliases for overlays */
     s->gnt_aliases = (void *)g_new0(MemoryRegion, s->max_frames);
@@ -90,8 +88,11 @@ static void xen_gnttab_realize(DeviceState *dev, Error **errp)
         s->gnt_frame_gpas[i] = INVALID_GPA;
     }
 
+    s->nr_frames = 0;
+    memset(s->entries.v1, 0, XEN_PAGE_SIZE * s->max_frames);
     s->entries.v1[GNTTAB_RESERVED_XENSTORE].flags = GTF_permit_access;
     s->entries.v1[GNTTAB_RESERVED_XENSTORE].frame = XEN_SPECIAL_PFN(XENSTORE);
+
     qemu_mutex_init(&s->gnt_lock);
 
     xen_gnttab_singleton = s;
@@ -524,3 +525,24 @@ static struct gnttab_backend_ops emu_gnttab_backend_ops = {
     .unmap = xen_be_gnttab_unmap,
 };
 
+int xen_gnttab_reset(void)
+{
+    XenGnttabState *s = xen_gnttab_singleton;
+
+    if (!s) {
+        return -ENOTSUP;
+    }
+
+    QEMU_LOCK_GUARD(&s->gnt_lock);
+
+    s->nr_frames = 0;
+
+    memset(s->entries.v1, 0, XEN_PAGE_SIZE * s->max_frames);
+
+    s->entries.v1[GNTTAB_RESERVED_XENSTORE].flags = GTF_permit_access;
+    s->entries.v1[GNTTAB_RESERVED_XENSTORE].frame = XEN_SPECIAL_PFN(XENSTORE);
+
+    memset(s->map_track, 0, s->max_frames * ENTRIES_PER_FRAME_V1);
+
+    return 0;
+}
diff --git a/hw/i386/kvm/xen_gnttab.h b/hw/i386/kvm/xen_gnttab.h
index 3bdbe96191..ee215239b0 100644
--- a/hw/i386/kvm/xen_gnttab.h
+++ b/hw/i386/kvm/xen_gnttab.h
@@ -13,6 +13,7 @@
 #define QEMU_XEN_GNTTAB_H
 
 void xen_gnttab_create(void);
+int xen_gnttab_reset(void);
 int xen_gnttab_map_page(uint64_t idx, uint64_t gfn);
 
 struct gnttab_set_version;
diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c
index 7076e23453..273200bc70 100644
--- a/target/i386/kvm/xen-emu.c
+++ b/target/i386/kvm/xen-emu.c
@@ -1329,6 +1329,11 @@ static int kvm_xen_soft_reset(void)
         return err;
     }
 
+    err = xen_gnttab_reset();
+    if (err) {
+        return err;
+    }
+
     err = xen_xenstore_reset();
     if (err) {
         return err;
-- 
2.49.0