[Xen-changelog] [xen staging] x86/ioapic: fix clear_IO_APIC_pin write of raw entries

[patchbot@xxxxxxx]

commit dedcb1087dfeae0bbd9eea465a57f25b13e40585
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Tue Nov 12 11:07:40 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Nov 12 11:07:40 2019 +0100

    x86/ioapic: fix clear_IO_APIC_pin write of raw entries
    
    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 when fields are affected which may either have changed
    meaning with interrupt remapping, or which may need mirroring into
    IRTEs.
    
    Reported-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 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)
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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