[Xen-devel] [PATCH for-4.13 v2 2/2] x86/ioapic: fix clear_IO_APIC_pin write of raw entries

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

clear_IO_APIC_pin can be called after the iommu has been enabled, and
using raw reads and writes to modify IO-APIC entries that have been
setup to use interrupt remapping can lead to issues as some of the
fields have different meaning when the IO-APIC entry is setup to point
to an interrupt remapping table entry.

The following ASSERT in AMD IOMMU code triggers afterwards as a result
of the raw changes to IO-APIC entries performed by clear_IO_APIC_pin.

(XEN) [   10.082154] ENABLING IO-APIC IRQs
(XEN) [   10.087789]  -> Using new ACK method
(XEN) [   10.093738] Assertion 'get_rte_index(rte) == offset' failed at 
iommu_intr.c:328

Fix this by making sure that modifications to entries are performed in
non raw mode.

Reported-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Juergen Gross <jgross@xxxxxxxx>
---
Changes since v1:
 - Do not change all instances of raw reads.
 - Fix commit message
---
 xen/arch/x86/io_apic.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index b9c66acdb3..732b57995c 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -519,8 +519,9 @@ static void clear_IO_APIC_pin(unsigned int apic, unsigned 
int pin)
     if (entry.irr) {
         /* Make sure the trigger mode is set to level. */
         if (!entry.trigger) {
+            entry = __ioapic_read_entry(apic, pin, false);
             entry.trigger = 1;
-            __ioapic_write_entry(apic, pin, true, entry);
+            __ioapic_write_entry(apic, pin, false, entry);
         }
         __io_apic_eoi(apic, entry.vector, pin);
     }
@@ -530,7 +531,7 @@ static void clear_IO_APIC_pin(unsigned int apic, unsigned 
int pin)
      */
     memset(&entry, 0, sizeof(entry));
     entry.mask = 1;
-    __ioapic_write_entry(apic, pin, true, entry);
+    __ioapic_write_entry(apic, pin, false, entry);
 
     entry = __ioapic_read_entry(apic, pin, true);
     if (entry.irr)
-- 
2.23.0


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