Re: [PATCH 24/24] iommu/amd: Relocate vIOMMU translate-device-id on PCI reserve

["Suthikulpanit, Suravee" <suravee.suthikulpanit@amd.com>]

On 8/19/2026 4:42 PM, guanghuifeng@linux.alibaba.com wrote:
> 
> 在 2026/7/27 21:29, Suravee Suthikulpanit 写道:
>> When PCI attach reserves a BDF already allocated to a vIOMMU, relocate
>> that vIOMMU to a newly allocated translate-device-id before marking the
>> BDF reserved for the device.  Reprogram translation DTE and VFctrl under
>> trans_devid_lock; roll back the pool on failure.
>>
>> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
>> ---
>>   drivers/iommu/amd/trans_devid.c | 116 +++++++++++++++++++++++++++++++-
>>   1 file changed, 115 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/amd/trans_devid.c b/drivers/iommu/amd/ 
>> trans_devid.c
>> index 9d7d93c5dcdb..6fb1ba3c9444 100644
>> --- a/drivers/iommu/amd/trans_devid.c
>> +++ b/drivers/iommu/amd/trans_devid.c
>> @@ -82,16 +82,120 @@ void amd_iommu_pci_seg_trans_devid_fini(struct 
>>
>> ....
>>
>> +static int trans_devid_relocate(struct amd_iommu_pci_seg *pci_seg, 
>> u16 from_id,
>> +                struct amd_iommu_viommu *aviommu)
>> +{
>> +    u16 new_id;
>> +    int ret;
>> +
>> +    mutex_lock(&aviommu->trans_devid_lock);
>> +
>> +    mutex_lock(&pci_seg->trans_devid_mutex);
>> +    if (trans_devid_xa_owner(xa_load(&pci_seg->trans_devid_xa, 
>> from_id)) !=
>> +        aviommu) {
>> +        ret = -ENOENT;
>> +        goto unlock_seg;
>> +    }
>> +
>> +    if (aviommu->trans_devid != from_id) {
>> +        ret = -EINVAL;
>> +        goto unlock_seg;
>> +    }
>> +
>> +    new_id = trans_devid_find_free_locked(pci_seg);
>> +    if (new_id < 0) {
>> +        ret = new_id;
>> +        goto unlock_seg;
>> +    }
> 
> 
> This has a type-truncation bug. trans_devid_find_free_locked() returns
> int and signals failure with -ENOSPC. Assigning it to a u16 truncates
> -ENOSPC (-28) to 65508 (0xFFDC), and the subsequent "if (new_id < 0)"
> is always false for an unsigned u16. On pool exhaustion the code would
> proceed to install and program a DTE with the bogus ID 65508. Please
> change new_id to int:
> 
>      int new_id;
> 

I'll fix in v5.

Thanks,
Suravee