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

[Heiko Carstens <hca@linux.ibm.com>]

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.