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

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Date:   Tue, 22 Sep 2020 10:06:10 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Niklas Schnelle <schnelle@...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

On 9/21/20 5:41 AM, Niklas Schnelle wrote:
> 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.

Frankly, the dropping of 'str_' was arbitrary on my part -- I'll go 
ahead and rename it to util_str_avail with v2.

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

Thanks!

>> +	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++) {
>>