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

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

> 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



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