This is a note to let you know that I've just added the patch titled
Xen/gnttab: handle p2m update errors on a per-slot basis
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-gnttab-handle-p2m-update-errors-on-a-per-slot-basis.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8310b77b48c5558c140e7a57a702e7819e62f04e Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@xxxxxxxx>
Date: Thu, 25 Feb 2021 16:34:43 +0100
Subject: Xen/gnttab: handle p2m update errors on a per-slot basis
From: Jan Beulich <jbeulich@xxxxxxxx>
commit 8310b77b48c5558c140e7a57a702e7819e62f04e upstream.
Bailing immediately from set_foreign_p2m_mapping() upon a p2m updating
error leaves the full batch in an ambiguous state as far as the caller
is concerned. Instead flags respective slots as bad, unmapping what
was mapped there right away.
HYPERVISOR_grant_table_op()'s return value and the individual unmap
slots' status fields get used only for a one-time - there's not much we
can do in case of a failure.
Note that there's no GNTST_enomem or alike, so GNTST_general_error gets
used.
The map ops' handle fields get overwritten just to be on the safe side.
This is part of XSA-367.
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Link: https://lore.kernel.org/r/96cccf5d-e756-5f53-b91a-ea269bfb9be0@xxxxxxxx
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/xen/p2m.c | 35 +++++++++++++++++++++++++++++++----
arch/x86/xen/p2m.c | 44 +++++++++++++++++++++++++++++++++++++++++---
2 files changed, 72 insertions(+), 7 deletions(-)
--- a/arch/arm/xen/p2m.c
+++ b/arch/arm/xen/p2m.c
@@ -91,12 +91,39 @@ int set_foreign_p2m_mapping(struct gntta
int i;
for (i = 0; i < count; i++) {
+ struct gnttab_unmap_grant_ref unmap;
+ int rc;
+
if (map_ops[i].status)
continue;
- if (unlikely(!set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT,
- map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT))) {
- return -ENOMEM;
- }
+ if (likely(set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT,
+ map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT)))
+ continue;
+
+ /*
+ * Signal an error for this slot. This in turn requires
+ * immediate unmapping.
+ */
+ map_ops[i].status = GNTST_general_error;
+ unmap.host_addr = map_ops[i].host_addr,
+ unmap.handle = map_ops[i].handle;
+ map_ops[i].handle = ~0;
+ if (map_ops[i].flags & GNTMAP_device_map)
+ unmap.dev_bus_addr = map_ops[i].dev_bus_addr;
+ else
+ unmap.dev_bus_addr = 0;
+
+ /*
+ * Pre-populate the status field, to be recognizable in
+ * the log message below.
+ */
+ unmap.status = 1;
+
+ rc = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
+ &unmap, 1);
+ if (rc || unmap.status != GNTST_okay)
+ pr_err_once("gnttab unmap failed: rc=%d st=%d\n",
+ rc, unmap.status);
}
return 0;
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -723,6 +723,8 @@ int set_foreign_p2m_mapping(struct gntta
for (i = 0; i < count; i++) {
unsigned long mfn, pfn;
+ struct gnttab_unmap_grant_ref unmap[2];
+ int rc;
/* Do not add to override if the map failed. */
if (map_ops[i].status != GNTST_okay ||
@@ -740,10 +742,46 @@ int set_foreign_p2m_mapping(struct gntta
WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be ballooned");
- if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
- ret = -ENOMEM;
- goto out;
+ if (likely(set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
+ continue;
+
+ /*
+ * Signal an error for this slot. This in turn requires
+ * immediate unmapping.
+ */
+ map_ops[i].status = GNTST_general_error;
+ unmap[0].host_addr = map_ops[i].host_addr,
+ unmap[0].handle = map_ops[i].handle;
+ map_ops[i].handle = ~0;
+ if (map_ops[i].flags & GNTMAP_device_map)
+ unmap[0].dev_bus_addr = map_ops[i].dev_bus_addr;
+ else
+ unmap[0].dev_bus_addr = 0;
+
+ if (kmap_ops) {
+ kmap_ops[i].status = GNTST_general_error;
+ unmap[1].host_addr = kmap_ops[i].host_addr,
+ unmap[1].handle = kmap_ops[i].handle;
+ kmap_ops[i].handle = ~0;
+ if (kmap_ops[i].flags & GNTMAP_device_map)
+ unmap[1].dev_bus_addr = kmap_ops[i].dev_bus_addr;
+ else
+ unmap[1].dev_bus_addr = 0;
}
+
+ /*
+ * Pre-populate both status fields, to be recognizable in
+ * the log message below.
+ */
+ unmap[0].status = 1;
+ unmap[1].status = 1;
+
+ rc = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
+ unmap, 1 + !!kmap_ops);
+ if (rc || unmap[0].status != GNTST_okay ||
+ unmap[1].status != GNTST_okay)
+ pr_err_once("gnttab unmap failed: rc=%d st0=%d st1=%d\n",
+ rc, unmap[0].status, unmap[1].status);
}
out:
Patches currently in stable-queue which might be from jbeulich@xxxxxxxx are
queue-4.4/xen-netback-respect-gnttab_map_refs-s-return-value.patch
queue-4.4/xen-gnttab-handle-p2m-update-errors-on-a-per-slot-basis.patch
