Re: [PATCH v1] s390: ipl: fix physical-virtual confusion for diag308

[Alexander Gordeev <agordeev@linux.ibm.com>]

On Fri, Mar 10, 2023 at 01:22:04PM +0100, Nico Boehr wrote:
> Diag 308 subcodes expect a physical address as their parameter.
> 
> This currently is not a bug, but in the future physical and virtual
> addresses might differ.
> 
> Fix the confusion by doing a virtual-to-physical conversion in the
> exported diag308() and leave the assembly wrapper __diag308() alone.
> 
> Note that several callers pass NULL as addr, this is fine since
> virt_to_phys(0) == 0.
> 
> Suggested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> ---
>  arch/s390/kernel/ipl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
> index 5f0f5c86963a..5611ba8f68b9 100644
> --- a/arch/s390/kernel/ipl.c
> +++ b/arch/s390/kernel/ipl.c
> @@ -176,7 +176,7 @@ static bool reipl_fcp_clear;
>  static bool reipl_ccw_clear;
>  static bool reipl_eckd_clear;
>  
> -static inline int __diag308(unsigned long subcode, void *addr)
> +static inline int __diag308(unsigned long subcode, u64 addr)
>  {
>  	union register_pair r1;
>  
> @@ -195,7 +195,7 @@ static inline int __diag308(unsigned long subcode, void *addr)
>  int diag308(unsigned long subcode, void *addr)
>  {
>  	diag_stat_inc(DIAG_STAT_X308);
> -	return __diag308(subcode, addr);
> +	return __diag308(subcode, virt_to_phys(addr));
>  }
>  EXPORT_SYMBOL_GPL(diag308);

Please note diag308() is called with NULL a lot.
I think a proper fix would be like this:

diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
index 0f91cd401eef..43de939b7af1 100644
--- a/arch/s390/kernel/ipl.c
+++ b/arch/s390/kernel/ipl.c
@@ -176,11 +176,11 @@ static bool reipl_fcp_clear;
 static bool reipl_ccw_clear;
 static bool reipl_eckd_clear;
 
-static inline int __diag308(unsigned long subcode, void *addr)
+static inline int __diag308(unsigned long subcode, unsigned long addr)
 {
 	union register_pair r1;
 
-	r1.even = (unsigned long) addr;
+	r1.even = addr;
 	r1.odd	= 0;
 	asm volatile(
 		"	diag	%[r1],%[subcode],0x308\n"
@@ -195,7 +195,7 @@ static inline int __diag308(unsigned long subcode, void *addr)
 int diag308(unsigned long subcode, void *addr)
 {
 	diag_stat_inc(DIAG_STAT_X308);
-	return __diag308(subcode, addr);
+	return __diag308(subcode, addr ? virt_to_phys(addr) : 0);
 }
 EXPORT_SYMBOL_GPL(diag308);