Re: [PATCH] iommu/amd: Fix "Guest Virtual APIC Table Root Pointer" configuration in IRTE

[Kishon VijayAbraham I <kvijayab@amd.com>]

Hi Joao,

On 4/3/2023 3:41 PM, Joao Martins wrote:
> On 03/04/2023 05:29, Suthikulpanit, Suravee wrote:
>> Kishon,
>>
>> On 3/31/2023 1:17 PM, Kishon Vijay Abraham I wrote:
>>> commit b9c6ff94e43a ("iommu/amd: Re-factor guest virtual APIC
>>> (de-)activation code") while refactoring guest virtual APIC
>>> activation/de-activation code, stored information for activate/de-activate
>>> in "struct amd_ir_data". It used 32-bit integer data type for storing the
>>> "Guest Virtual APIC Table Root Pointer" (ga_root_ptr), though the
>>> "ga_root_ptr" is actually a 40-bit field in IRTE (Interrupt Remapping
>>> Table Entry).
>>>
>>> This causes interrupts from PCIe devices to not reach the guest in the case
>>> of PCIe passthrough with SME (Secure Memory Encryption) enabled as _SME_
>>> bit in the "ga_root_ptr" is lost before writing it to the IRTE.
>>>
>>> Fix it by using 64-bit data type for storing the "ga_root_ptr".
>>>
>>> Fixes: b9c6ff94e43a ("iommu/amd: Re-factor guest virtual APIC (de-)activation
>>> code")
>>> Cc: stable@vger.kernel.org # v5.4+
>>> Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
>>> Signed-off-by: Kishon Vijay Abraham I <kvijayab@amd.com>
>>
>> Please also add
>> Reported-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
>> ---
>>   drivers/iommu/amd/amd_iommu_types.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
>> index 3d684190b4d5..990614b8a1fe 100644
>> --- a/drivers/iommu/amd/amd_iommu_types.h
>> +++ b/drivers/iommu/amd/amd_iommu_types.h
>> @@ -1001,7 +1001,7 @@ struct amd_ir_data {
>>   	 */
>>   	struct irq_cfg *cfg;
>>   	int ga_vector;
>> -	int ga_root_ptr;
>> +	u64 ga_root_ptr;
>>   	int ga_tag;
>>   };
> 
> Nice catch. While at it I noticed the following:
> 
> * ga_tag: The conversion of uint (in kvm as they use proper u32 for gatag) to
> int will miss a bit thus at least VM IDs with the msb set will be stripped from
> vCPU wake ups? Fortunately the 24 bits for VCPU ID wouldn't be affected. But
> ga_tag should probably be a u32.
> 
> * ga_vector: this in principle should be u8 per spec, maybe it is OK to stay as
> is to prevent compiler warnings as IOMMU intremap struct vcpu_data is using a u32.

Thank you for reviewing. Will add fix for other data types in my v2 of 
this patch.

Regards,
Kishon