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

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

On 4/23/15, 12:59, "Sander Eikelenboom" <linux@xxxxxxxxxxxxxx> wrote:

>
>> 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
>
>If it crashes with:
>
>
>That problem is likely solved by another patch:
>
>http://lists.xen.org/archives/html/xen-devel/2015-04/msg02253.html
>

Yes, this has fixed the crash.

Thanks,

Suravee

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