Re: [PATCH] s390/cmf: Fix virtual vs physical address confusion

[Peter Oberparleiter <oberpar@linux.ibm.com>]

On 20.09.2026 18:15, Heiko Carstens wrote:
> On Fri, Sep 18, 2026 at 06:12:07PM +0200, Peter Oberparleiter wrote:
>> The measurement block address is an absolute address; therefore add a
>> missing virt_to_phys() translation.
>>
>> Without this fix, a wrong address will be used by firmware when storing
>> extended format channel measurement data on kernels built with
>> CONFIG_RANDOMIZE_IDENTITY_BASE=y.
>>
>> Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
>> ---
>>  drivers/s390/cio/cmf.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/s390/cio/cmf.c b/drivers/s390/cio/cmf.c
>> index 92ab3d546fe4..5f57a12762d2 100644
>> --- a/drivers/s390/cio/cmf.c
>> +++ b/drivers/s390/cio/cmf.c
>> @@ -183,7 +183,7 @@ static int set_schib(struct ccw_device *cdev, u32 mme, int mbfc,
>>  	sch->config.mbfc = mbfc;
>>  	/* address can be either a block address or a block index */
>>  	if (mbfc)
>> -		sch->config.mba = address;
>> +		sch->config.mba = address ? virt_to_phys((void *)address) : 0;
> 
> Would it make sense to change the type of the mba member in struct
> schib_config and struct schib to dma64_t, and use virt_to_dma64()
> instead of virt_to_phys() here?
> 
> That would add sparse type checking and would catch similar future bugs.

Sounds good - I'll prepare a v2.


-- 
Peter Oberparleiter
Linux on IBM Z Development - IBM Germany R&D