Re: [Xen-devel] [PATCH] AMD IOMMU: only translate remapped IO-APIC RTEs

["Suthikulpanit, Suravee" <Suravee.Suthikulpanit@xxxxxxx>]

On 4/23/15, 08:47, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:

>>>> On 23.04.15 at 15:31, <Suravee.Suthikulpanit@xxxxxxx> wrote:
>
>> 
>> On 4/17/15, 10:27, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
>> 
>>>1aeb1156fa ("x86 don't change affinity with interrupt unmasked")
>>>introducing RTE reads prior to the respective interrupt having got
>>>enabled for the first time uncovered a bug in 2ca9fbd739 ("AMD IOMMU:
>>>allocate IRTE entries instead of using a static mapping"): We obviously
>>>shouldn't be translating RTEs for which remapping didn't get set up
>>>yet.
>>>
>>>Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
>>>Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>
>>>--- a/xen/drivers/passthrough/amd/iommu_intr.c
>>>+++ b/xen/drivers/passthrough/amd/iommu_intr.c
>>>@@ -365,15 +365,17 @@ unsigned int amd_iommu_read_ioapic_from_
>>>     unsigned int apic, unsigned int reg)
>>> {
>>>     unsigned int val = __io_apic_read(apic, reg);
>>>+    unsigned int pin = (reg - 0x10) / 2;
>>>+    unsigned int offset = ioapic_sbdf[IO_APIC_ID(apic)].pin_2_idx[pin];
>>> 
>>>-    if ( !(reg & 1) )
>>>+    if ( !(reg & 1) && offset < INTREMAP_ENTRIES )
>>>     {
>>>-        unsigned int offset = val & (INTREMAP_ENTRIES - 1);
>>>         u16 bdf = ioapic_sbdf[IO_APIC_ID(apic)].bdf;
>>>         u16 seg = ioapic_sbdf[IO_APIC_ID(apic)].seg;
>>>         u16 req_id = get_intremap_requestor_id(seg, bdf);
>>>         const u32 *entry = get_intremap_entry(seg, req_id, offset);
>>> 
>>>+        ASSERT(offset == (val & (INTREMAP_ENTRIES - 1)));
>> 
>> Jan, could you please explain why the ASSERT is needed here?
>
>The previous value "offset" got assigned was calculated using
>the right side expression. I.e. the assert makes sure that what
>we used before and what we use now is the same.
>
>Jan

Jan,

I have tested this patch w/ staging branch booting Dom0, and this patch
got rid of the following error from xl dmesg:
(XEN) APIC error on CPU0: 00(40)
(XEN) APIC error on CPU2: 00(40)

However, when I tried starting a guest w/ PCI device passthrough, the
system crashed and reboot. Although, I don¹t think this is caused by the
patch. 

Acked-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>

I¹m looking into the issue. I also went back and tested it with 4.5 on the
same setup and didn¹t see the issue.


Thanks,
Suravee


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