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SubjectRe: [PATCH] iommu/amd: fix interrupt remapping for avic
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On 9/15/20 6:25 PM, Maxim Levitsky wrote:
> On Mon, 2020-09-14 at 21:48 +0700, Suravee Suthikulpanit wrote:
>> Maxim,
>>
>> On 9/13/2020 7:42 PM, Maxim Levitsky wrote:
>>> Commit e52d58d54a32 ("iommu/amd: Use cmpxchg_double() when updating 128-bit IRTE")
>>> accidentally removed an assumption that modify_irte_ga always set the valid bit
>>> and amd_iommu_activate_guest_mode relied on that.
>>>
>>> Side effect of this is that on my machine, VFIO based VMs with AVIC enabled
>>> would eventually crash and show IOMMU errors like that:
>>>
>>> AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0055 address=0xfffffffdf8000000 flags=0x0008]
>>>
>>> Fixes: e52d58d54a321 ("iommu/amd: Use cmpxchg_double() when updating 128-bit IRTE")
>>> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
>>> ---
>>> drivers/iommu/amd/iommu.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
>>> index 07ae8b93887e5..aff4cc1869356 100644
>>> --- a/drivers/iommu/amd/iommu.c
>>> +++ b/drivers/iommu/amd/iommu.c
>>> @@ -3853,6 +3853,7 @@ int amd_iommu_activate_guest_mode(void *data)
>>> entry->hi.fields.ga_root_ptr = ir_data->ga_root_ptr;
>>> entry->hi.fields.vector = ir_data->ga_vector;
>>> entry->lo.fields_vapic.ga_tag = ir_data->ga_tag;
>>> + entry->lo.fields_remap.valid = 1;
>>>
>>> return modify_irte_ga(ir_data->irq_2_irte.devid,
>>> ir_data->irq_2_irte.index, entry, ir_data);
>>>
>>
>> Could you please try with the following patch instead?
>>
>> --- a/drivers/iommu/amd/iommu.c
>> +++ b/drivers/iommu/amd/iommu.c
>> @@ -3840,14 +3840,18 @@ int amd_iommu_activate_guest_mode(void *data)
>> {
>> struct amd_ir_data *ir_data = (struct amd_ir_data *)data;
>> struct irte_ga *entry = (struct irte_ga *) ir_data->entry;
>> + u64 valid;
>>
>> if (!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir) ||
>> !entry || entry->lo.fields_vapic.guest_mode)
>> return 0;
>>
>> + valid = entry->lo.fields_vapic.valid;
>> +
>> entry->lo.val = 0;
>> entry->hi.val = 0;
>>
>> + entry->lo.fields_vapic.valid = valid;
>> entry->lo.fields_vapic.guest_mode = 1;
>> entry->lo.fields_vapic.ga_log_intr = 1;
>> entry->hi.fields.ga_root_ptr = ir_data->ga_root_ptr;
>> @@ -3864,12 +3868,14 @@ int amd_iommu_deactivate_guest_mode(void *data)
>> struct amd_ir_data *ir_data = (struct amd_ir_data *)data;
>> struct irte_ga *entry = (struct irte_ga *) ir_data->entry;
>> struct irq_cfg *cfg = ir_data->cfg;
>> - u64 valid = entry->lo.fields_remap.valid;
>> + u64 valid;
>>
>> if (!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir) ||
>> !entry || !entry->lo.fields_vapic.guest_mode)
>> return 0;
>>
>> + valid = entry->lo.fields_remap.valid;
>> +
>> entry->lo.val = 0;
>> entry->hi.val = 0;
> I see. I based my approach on the fact that valid bit was
> set always to true anyway before, plus that amd_iommu_activate_guest_mode
> should be really only called when someone activates a valid interrupt remapping
> entry, but IMHO the approach of preserving the valid bit is safer anyway.
>
> It works on my system (I applied the patch manually, since either your or my email client,
> seems to mangle the patch)
>
> Thanks,
> Best regards,
> Maxim Levitsky
>
>

Sorry for the mangled patch. I'll submit the patch w/ your information. Thanks for your help reporting, debugging, and
testing the patch.

Sincerely,

Suravee
>> --
>
>>
>> Thanks,
>> Suravee
>>
>
>

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