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Date:   Tue, 19 Apr 2022 11:41:46 +0200
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Subject: Re: [PATCH v5 18/21] vfio-pci/zdev: different maxstbl for interpreted
 devices
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To:     Matthew Rosato <mjrosato@linux.ibm.com>, linux-s390@vger.kernel.org
Cc:     alex.williamson@redhat.com, cohuck@redhat.com,
        schnelle@linux.ibm.com, farman@linux.ibm.com,
        borntraeger@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com,
        gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com,
        svens@linux.ibm.com, frankja@linux.ibm.com, david@redhat.com,
        imbrenda@linux.ibm.com, vneethv@linux.ibm.com,
        oberpar@linux.ibm.com, freude@linux.ibm.com, thuth@redhat.com,
        pasic@linux.ibm.com, pbonzini@redhat.com, corbet@lwn.net,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org
References: <20220404174349.58530-1-mjrosato@linux.ibm.com>
 <20220404174349.58530-19-mjrosato@linux.ibm.com>
From:   Pierre Morel <pmorel@linux.ibm.com>
In-Reply-To: <20220404174349.58530-19-mjrosato@linux.ibm.com>
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On 4/4/22 19:43, Matthew Rosato wrote:
> When doing load/store interpretation, the maximum store block length is
> determined by the underlying firmware, not the host kernel API.  Reflect
> that in the associated Query PCI Function Group clp capability and let
> userspace decide which is appropriate to present to the guest.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>


Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>


> ---
>   drivers/vfio/pci/vfio_pci_zdev.c | 6 ++++--
>   include/uapi/linux/vfio_zdev.h   | 4 ++++
>   2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
> index 4a653ce480c7..d3ca58d9d8ec 100644
> --- a/drivers/vfio/pci/vfio_pci_zdev.c
> +++ b/drivers/vfio/pci/vfio_pci_zdev.c
> @@ -44,14 +44,16 @@ static int zpci_group_cap(struct zpci_dev *zdev, struct vfio_info_cap *caps)
>   {
>   	struct vfio_device_info_cap_zpci_group cap = {
>   		.header.id = VFIO_DEVICE_INFO_CAP_ZPCI_GROUP,
> -		.header.version = 1,
> +		.header.version = 2,
>   		.dasm = zdev->dma_mask,
>   		.msi_addr = zdev->msi_addr,
>   		.flags = VFIO_DEVICE_INFO_ZPCI_FLAG_REFRESH,
>   		.mui = zdev->fmb_update,
>   		.noi = zdev->max_msi,
>   		.maxstbl = ZPCI_MAX_WRITE_SIZE,
> -		.version = zdev->version
> +		.version = zdev->version,
> +		.reserved = 0,
> +		.imaxstbl = zdev->maxstbl
>   	};
>   
>   	return vfio_info_add_capability(caps, &cap.header, sizeof(cap));
> diff --git a/include/uapi/linux/vfio_zdev.h b/include/uapi/linux/vfio_zdev.h
> index 78c022af3d29..77f2aff1f27e 100644
> --- a/include/uapi/linux/vfio_zdev.h
> +++ b/include/uapi/linux/vfio_zdev.h
> @@ -50,6 +50,10 @@ struct vfio_device_info_cap_zpci_group {
>   	__u16 noi;		/* Maximum number of MSIs */
>   	__u16 maxstbl;		/* Maximum Store Block Length */
>   	__u8 version;		/* Supported PCI Version */
> +	/* End of version 1 */
> +	__u8 reserved;
> +	__u16 imaxstbl;		/* Maximum Interpreted Store Block Length */
> +	/* End of version 2 */
>   };
>   
>   /**
> 

-- 
Pierre Morel
IBM Lab Boeblingen