Re: [PATCH v1 1/1] s390: nmi: fix virtual-physical address confusion

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Wed, 15 Feb 2023 17:02:52 +0100
Nico Boehr <nrb@linux.ibm.com> wrote:

> When a machine check is received while in SIE, it is reinjected into the
> guest in some cases. The respective code needs to access the sie_block,
> which is taken from the backed up R14.
> 
> Since reinjection only occurs while we are in SIE (i.e. between the
> labels sie_entry and sie_leave in entry.S and thus if CIF_MCCK_GUEST is
> set), the backed up R14 will always contain a physical address in
> s390_backup_mcck_info.
> 
> This currently works, because virtual and physical addresses are
> the same.
> 
> Add phys_to_virt() to resolve the virtual-physical confusion.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  arch/s390/kernel/nmi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
> index 5dbf274719a9..322160328866 100644
> --- a/arch/s390/kernel/nmi.c
> +++ b/arch/s390/kernel/nmi.c
> @@ -347,7 +347,7 @@ static void notrace s390_backup_mcck_info(struct pt_regs *regs)
>  
>  	/* r14 contains the sie block, which was set in sie64a */
>  	struct kvm_s390_sie_block *sie_block =
> -			(struct kvm_s390_sie_block *) regs->gprs[14];
> +			(struct kvm_s390_sie_block *)phys_to_virt(regs->gprs[14]);
>  
>  	if (sie_block == NULL)
>  		/* Something's seriously wrong, stop system. */