Re: [PATCH v4 01/12] vfio/pci: Extract mdev check into an helper

[Joao Martins]

On 16/07/2024 10:21, Cédric Le Goater wrote:
> Hello Joao
> 
> On 7/12/24 13:46, Joao Martins wrote:
>> In preparation to skip initialization of the HostIOMMUDevice for mdev,
>> extract the checks that validate if a device is an mdev into helpers.
>>
>> A vfio_set_mdev() is created, and subsystems consult VFIODevice::mdev
>> to check if it's mdev or not.
>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>>   include/hw/vfio/vfio-common.h |  2 ++
>>   hw/vfio/helpers.c             | 18 ++++++++++++++++++
>>   hw/vfio/pci.c                 |  9 ++-------
>>   3 files changed, 22 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>> index e8ddf92bb185..7419466bca92 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -116,6 +116,7 @@ typedef struct VFIODevice {
>>       DeviceState *dev;
>>       int fd;
>>       int type;
>> +    bool mdev;
>>       bool reset_works;
>>       bool needs_reset;
>>       bool no_mmap;
>> @@ -231,6 +232,7 @@ void vfio_region_exit(VFIORegion *region);
>>   void vfio_region_finalize(VFIORegion *region);
>>   void vfio_reset_handler(void *opaque);
>>   struct vfio_device_info *vfio_get_device_info(int fd);
>> +void vfio_set_mdev(VFIODevice *vbasedev);
>>   bool vfio_attach_device(char *name, VFIODevice *vbasedev,
>>                           AddressSpace *as, Error **errp);
>>   void vfio_detach_device(VFIODevice *vbasedev);
>> diff --git a/hw/vfio/helpers.c b/hw/vfio/helpers.c
>> index b14edd46edc9..bace0e788a09 100644
>> --- a/hw/vfio/helpers.c
>> +++ b/hw/vfio/helpers.c
>> @@ -675,3 +675,21 @@ int vfio_device_get_aw_bits(VFIODevice *vdev)
>>         return HOST_IOMMU_DEVICE_CAP_AW_BITS_MAX;
>>   }
>> +
>> +void vfio_set_mdev(VFIODevice *vbasedev)
> 
> Could you please change this routine to :
> 
>   bool vfio_device_is_mdev(VFIODevice *vbasedev)
> 
OK

>> +{
>> +    g_autofree char *tmp = NULL;
>> +    char *subsys;
> 
> a g_autofree variable is preferable here.
> 

It was a code move hence why I kept the exact same structure

I will change to your suggestion

>> +    bool is_mdev;
>> +
>> +    if (!vbasedev->sysfsdev) {
>> +        return;
>> +    }
>> +
>> +    tmp = g_strdup_printf("%s/subsystem", vbasedev->sysfsdev);
>> +    subsys = realpath(tmp, NULL);
>> +    is_mdev = subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
> 
> simply return is the result here and ....
> 
OK
>> +    free(subsys);
>> +
>> +    vbasedev->mdev = is_mdev;
>> +}
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index e03d9f3ba546..585f23a18406 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -2963,12 +2963,10 @@ static void vfio_realize(PCIDevice *pdev, Error 
>> **errp)
>>       ERRP_GUARD();
>>       VFIOPCIDevice *vdev = VFIO_PCI(pdev);
>>       VFIODevice *vbasedev = &vdev->vbasedev;
>> -    char *subsys;
>>       int i, ret;
>>       bool is_mdev;
>>       char uuid[UUID_STR_LEN];
>>       g_autofree char *name = NULL;
>> -    g_autofree char *tmp = NULL;
>>         if (vbasedev->fd < 0 && !vbasedev->sysfsdev) {
>>           if (!(~vdev->host.domain || ~vdev->host.bus ||
>> @@ -2997,11 +2995,8 @@ static void vfio_realize(PCIDevice *pdev, Error 
>> **errp)
>>        * stays in sync with the active working set of the guest driver.  
>> Prevent
>>        * the x-balloon-allowed option unless this is minimally an mdev 
>> device.
>>        */
>> -    tmp = g_strdup_printf("%s/subsystem", vbasedev->sysfsdev);
>> -    subsys = realpath(tmp, NULL);
>> -    is_mdev = subsys && (strcmp(subsys, "/sys/bus/mdev") == 0);
>> -    free(subsys);
>> -
>> +    vfio_set_mdev(vbasedev);
>> +    is_mdev = vbasedev->mdev;
> 
> replace with :
> 
>   vbasedev->mdev = vfio_device_is_mdev(vbasedev);
> 
> and use vbasedev->mdev instead of is_mdev where needed.
> 

OK

> 
> Thanks,
> 
> C.
> 
> 
> 
> 
>>       trace_vfio_mdev(vbasedev->name, is_mdev);
>>         if (vbasedev->ram_block_discard_allowed && !is_mdev) {
>