Re: [PATCH v2 2/5] powerpc/pseries: Add RTAS error injection buffer infrastructure

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 27/05/26 12:54, Narayana Murty N wrote:
> Adds global infrastructure required by the injection engine:
>   - a 1KB aligned RTAS working buffer in rtas.c
>   - a spinlock to serialize buffer access
>   - UAPI definitions for error-injection tokens (added to eeh.h)
>
> Signed-off-by: Narayana Murty N <nnmlinux@linux.ibm.com>
> ---
>   arch/powerpc/include/asm/rtas.h     | 21 +++++++++++++++++++++
>   arch/powerpc/include/uapi/asm/eeh.h | 18 ++++++++++++++++++
>   arch/powerpc/kernel/rtas.c          | 12 ++++++++++++
>   3 files changed, 51 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
> index d046bbd5017d..82512f822c7a 100644
> --- a/arch/powerpc/include/asm/rtas.h
> +++ b/arch/powerpc/include/asm/rtas.h
> @@ -519,6 +519,27 @@ int rtas_get_error_log_max(void);
>   extern spinlock_t rtas_data_buf_lock;
>   extern char rtas_data_buf[RTAS_DATA_BUF_SIZE];
>   
> +/*
> + * RTAS Error Injection Buffer (PAPR-compliant)
> + * ============================================
> + *
> + * 1KB aligned, zero-initialized buffer for ibm,errinjct RTAS work area.
> + * Protected by rtas_errinjct_buf_lock for concurrent access safety.
> + *
> + * PAPR Requirement: ibm,errinjct requires a caller-allocated buffer passed
> + * via physical address. Buffer must accommodate largest error type layouts:
> + * - IOA bus error (64-bit): 8x32-bit words (32 bytes)
> + * - All other types: <=4x32-bit words (16 bytes)
> + *
> + * Usage:
> + * prepare_errinjct_buffer() -> spin_lock() -> rtas_call() -> spin_unlock()
> + *
> + * Alignment: SZ_1K ensures PAPR firmware requirements and cache-line safety.
> + */
> +#define RTAS_ERRINJCT_BUF_SIZE 1024
> +extern spinlock_t rtas_errinjct_buf_lock;
> +extern char rtas_errinjct_buf[RTAS_ERRINJCT_BUF_SIZE];

The kernel has a similar buffer for userspace (named rtas_rmo_buf),
which is allocated in the range (0, min(ppc64_rma_size, 
RTAS_INSTANTIATE_MAX)).

Whereas, the base address of the statically allocated rtas_errinjct_buf 
array
depends on the location at which the kernel is loaded, which could be 
higher than
RTAS_INSTANTIATE_MAX.

Also, things will break if the base address of rtas_errinjct_buf is 
greater than
4 GB. In that case, the kernel will send a truncated address, and RTAS may
corrupt memory as a result.

Why don't we allocate rtas_errinjct_buf in the same range where
rtas_rmo_buf is allocated?
> +
>   /* RMO buffer reserved for user-space RTAS use */
>   extern unsigned long rtas_rmo_buf;
>   
> diff --git a/arch/powerpc/include/uapi/asm/eeh.h b/arch/powerpc/include/uapi/asm/eeh.h
> index 3b5c47ff3fc4..86645cab2827 100644
> --- a/arch/powerpc/include/uapi/asm/eeh.h
> +++ b/arch/powerpc/include/uapi/asm/eeh.h
> @@ -41,4 +41,22 @@
>   #define EEH_ERR_FUNC_DMA_WR_TARGET	19
>   #define EEH_ERR_FUNC_MAX		19
>   
> +/* RTAS PCI Error Injection Token Types */
> +#define RTAS_ERR_TYPE_FATAL                     0x1
> +#define RTAS_ERR_TYPE_RECOVERED_RANDOM_EVENT    0x2
> +#define RTAS_ERR_TYPE_RECOVERED_SPECIAL_EVENT   0x3
> +#define RTAS_ERR_TYPE_CORRUPTED_PAGE            0x4
> +#define RTAS_ERR_TYPE_CORRUPTED_SLB             0x5
> +#define RTAS_ERR_TYPE_TRANSLATOR_FAILURE        0x6
> +#define RTAS_ERR_TYPE_IOA_BUS_ERROR             0x7
> +#define RTAS_ERR_TYPE_PLATFORM_SPECIFIC         0x8
> +#define RTAS_ERR_TYPE_CORRUPTED_DCACHE_START    0x9
> +#define RTAS_ERR_TYPE_CORRUPTED_DCACHE_END      0xA
> +#define RTAS_ERR_TYPE_CORRUPTED_ICACHE_START    0xB
> +#define RTAS_ERR_TYPE_CORRUPTED_ICACHE_END      0xC
> +#define RTAS_ERR_TYPE_CORRUPTED_TLB_START       0xD
> +#define RTAS_ERR_TYPE_CORRUPTED_TLB_END         0xE
> +#define RTAS_ERR_TYPE_IOA_BUS_ERROR_64          0xF
> +#define RTAS_ERR_TYPE_UPSTREAM_IO_ERROR         0x10
> +
>   #endif /* _ASM_POWERPC_EEH_H */
> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
> index a2dd94eed9d0..c110965ea1d9 100644
> --- a/arch/powerpc/kernel/rtas.c
> +++ b/arch/powerpc/kernel/rtas.c
> @@ -769,6 +769,18 @@ EXPORT_SYMBOL_GPL(rtas_data_buf);
>   
>   unsigned long rtas_rmo_buf;
>   
> +/*
> + * RTAS Error Injection Buffer - Global Definitions
> + * Global 1KB buffer and spinlock for ibm,errinjct RTAS service.
> + * Exported for pseries EEH error injection usage.
> + */
> +
> +DEFINE_SPINLOCK(rtas_errinjct_buf_lock);
> +EXPORT_SYMBOL_GPL(rtas_errinjct_buf_lock);
> +
> +char rtas_errinjct_buf[1024] __aligned(SZ_1K);
> +EXPORT_SYMBOL_GPL(rtas_errinjct_buf);
> +
>   /*
>    * If non-NULL, this gets called when the kernel terminates.
>    * This is done like this so rtas_flash can be a module.