linux-kernel - Re: [PATCH 2/4] s390/pci: track whether util_str is valid in the zpci

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Message-ID: <d1bc0e6b-2a9b-3de0-4dd6-59e26d6c1da4@linux.ibm.com>
Date:   Mon, 21 Sep 2020 11:41:14 +0200
From:   Niklas Schnelle <schnelle@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>,
        alex.williamson@...hat.com, cohuck@...hat.com
Cc:     pmorel@...ux.ibm.com, borntraeger@...ibm.com, hca@...ux.ibm.com,
        gor@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] s390/pci: track whether util_str is valid in the
 zpci_dev

Hi Matthew,

On 9/19/20 5:28 PM, Matthew Rosato wrote:
> We'll need to keep track of whether or not the byte string in util_str is
> valid and thus needs to be passed to a vfio-pci passthrough device.
> 
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> ---
>  arch/s390/include/asm/pci.h | 3 ++-
>  arch/s390/pci/pci_clp.c     | 1 +
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 882e233..32eb975 100644
> --- a/arch/s390/include/asm/pci.h
> +++ b/arch/s390/include/asm/pci.h
> @@ -132,7 +132,8 @@ struct zpci_dev {
>  	u8		rid_available	: 1;
>  	u8		has_hp_slot	: 1;
>  	u8		is_physfn	: 1;
> -	u8		reserved	: 5;
> +	u8		util_avail	: 1;

Any reason you're not matching the util_str_avail name in the response struct?
I think this is currently always an EBCDIC encoded string so the information that
even if it looks like binary for anyone with a non-mainframe background
it is in fact a string seems quite helpful.
Other than that

Acked-by: Niklas Schnelle <schnelle@...ux.ibm.com>

> +	u8		reserved	: 4;
>  	unsigned int	devfn;		/* DEVFN part of the RID*/
>  
>  	struct mutex lock;
> diff --git a/arch/s390/pci/pci_clp.c b/arch/s390/pci/pci_clp.c
> index 48bf316..d011134 100644
> --- a/arch/s390/pci/pci_clp.c
> +++ b/arch/s390/pci/pci_clp.c
> @@ -168,6 +168,7 @@ static int clp_store_query_pci_fn(struct zpci_dev *zdev,
>  	if (response->util_str_avail) {
>  		memcpy(zdev->util_str, response->util_str,
>  		       sizeof(zdev->util_str));
> +		zdev->util_avail = 1;
>  	}
>  	zdev->mio_capable = response->mio_addr_avail;
>  	for (i = 0; i < PCI_STD_NUM_BARS; i++) {
>