Ping: [PATCH] x86/fpu/xstate: Fix XSTATE_WARN_ON() to emit relevant diagnostics

[Andrew Cooper <Andrew.Cooper3@citrix.com>]

On 10/08/2022 23:19, Andrew Cooper wrote:
> "XSAVE consistency problem" has been reported under Xen, but that's the extent
> of my divination skills.
>
> Modify XSTATE_WARN_ON() to force the caller to provide relevant diagnostic
> information, and modify each caller suitably.
>
> For check_xstate_against_struct(), this removes a double WARN() where one will
> do perfectly fine.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Ingo Molnar <mingo@redhat.com>
> CC: Borislav Petkov <bp@alien8.de>
> CC: Dave Hansen <dave.hansen@linux.intel.com>
> CC: x86@kernel.org
> CC: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
>
> RFC: CC stable?  This has been wonky debugging for 7 years.
>
> Apparently "size 832 != kernel_size 0" so let the debugging continue...
> ---
>  arch/x86/kernel/fpu/xstate.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
> index c8340156bfd2..28b6478ea531 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -440,8 +440,8 @@ static void __init __xstate_dump_leaves(void)
>  	}
>  }
>  
> -#define XSTATE_WARN_ON(x) do {							\
> -	if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {	\
> +#define XSTATE_WARN_ON(x, fmt, ...) do {					\
> +	if (WARN_ONCE(x, "XSAVE consistency problem: " fmt, ##__VA_ARGS__)) {	\
>  		__xstate_dump_leaves();						\
>  	}									\
>  } while (0)
> @@ -554,8 +554,7 @@ static bool __init check_xstate_against_struct(int nr)
>  	    (nr >= XFEATURE_MAX) ||
>  	    (nr == XFEATURE_PT_UNIMPLEMENTED_SO_FAR) ||
>  	    ((nr >= XFEATURE_RSRVD_COMP_11) && (nr <= XFEATURE_RSRVD_COMP_16))) {
> -		WARN_ONCE(1, "no structure for xstate: %d\n", nr);
> -		XSTATE_WARN_ON(1);
> +		XSTATE_WARN_ON(1, "No structure for xstate: %d\n", nr);
>  		return false;
>  	}
>  	return true;
> @@ -598,12 +597,13 @@ static bool __init paranoid_xstate_size_valid(unsigned int kernel_size)
>  		 * XSAVES.
>  		 */
>  		if (!xsaves && xfeature_is_supervisor(i)) {
> -			XSTATE_WARN_ON(1);
> +			XSTATE_WARN_ON(1, "Got supervisor feature %d, but XSAVES not advertised\n", i);
>  			return false;
>  		}
>  	}
>  	size = xstate_calculate_size(fpu_kernel_cfg.max_features, compacted);
> -	XSTATE_WARN_ON(size != kernel_size);
> +	XSTATE_WARN_ON(size != kernel_size,
> +		       "size %u != kernel_size %u\n", size, kernel_size);
>  	return size == kernel_size;
>  }
>