[PATCH] powerpc/pseries: Fix plpks crash on non-pseries

[Nathan Chancellor]

On Wed, Sep 07, 2022 at 04:50:38PM +1000, Michael Ellerman wrote:
> As reported[1] by Nathan, the recently added plpks driver will crash if
> it's built into the kernel and booted on a non-pseries machine, eg
> powernv:
> 
>   kernel BUG at arch/powerpc/kernel/syscall.c:39!
>   Oops: Exception in kernel mode, sig: 5 [#1]
>   LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV
>   ...
>   NIP system_call_exception+0x90/0x3d0
>   LR  system_call_common+0xec/0x250
>   Call Trace:
>     0xc0000000035c3e10 (unreliable)
>     system_call_common+0xec/0x250
>   --- interrupt: c00 at plpar_hcall+0x38/0x60
>   NIP:  c0000000000e4300 LR: c00000000202945c CTR: 0000000000000000
>   REGS: c0000000035c3e80 TRAP: 0c00   Not tainted  (6.0.0-rc4)
>   MSR:  9000000002009033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE>  CR: 28000284  XER: 00000000
>   ...
>   NIP plpar_hcall+0x38/0x60
>   LR  pseries_plpks_init+0x64/0x23c
>   --- interrupt: c00
> 
> On powernv Linux is the hypervisor, so a hypercall just ends up going to
> the syscall path, which BUGs if the syscall (hypercall) didn't come from
> userspace.
> 
> The fix is simply to not probe the plpks driver on non-pseries machines.
> 
> [1] https://lore.kernel.org/linuxppc-dev/Yxe06fbq18Wv9y3W@dev-arch.thelio-3990X/
> 
> Fixes: 2454a7af0f2a ("powerpc/pseries: define driver for Platform KeyStore")
> Reported-by: Nathan Chancellor <nathan at kernel.org>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Tested-by: Nathan Chancellor <nathan at kernel.org>

Thanks!

> ---
>  arch/powerpc/platforms/pseries/plpks.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/plpks.c b/arch/powerpc/platforms/pseries/plpks.c
> index 52aaa2894606..f4b5b5a64db3 100644
> --- a/arch/powerpc/platforms/pseries/plpks.c
> +++ b/arch/powerpc/platforms/pseries/plpks.c
> @@ -17,6 +17,7 @@
>  #include <linux/string.h>
>  #include <linux/types.h>
>  #include <asm/hvcall.h>
> +#include <asm/machdep.h>
>  
>  #include "plpks.h"
>  
> @@ -457,4 +458,4 @@ static __init int pseries_plpks_init(void)
>  
>  	return rc;
>  }
> -arch_initcall(pseries_plpks_init);
> +machine_arch_initcall(pseries, pseries_plpks_init);
> -- 
> 2.37.2
>