linux-kernel - Re: [PATCH v4 1/3] RAS: Introduce AMD Address Translation Library

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Date: Mon, 18 Dec 2023 20:21:53 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Yazen Ghannam <yazen.ghannam@....com>, bp@...en8.de,
 linux-edac@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, avadhut.naik@....com, tony.luck@...el.com,
 john.allen@....com, william.roche@...cle.com, muralidhara.mk@....com
Subject: Re: [PATCH v4 1/3] RAS: Introduce AMD Address Translation Library

Le 18/12/2023 à 20:04, Yazen Ghannam a écrit :
> AMD Zen-based systems report memory errors through Machine Check banks
> representing Unified Memory Controllers (UMCs). The address value
> reported for DRAM ECC errors is a "normalized address" that is relative
> to the UMC. This normalized address must be converted to a system
> physical address to be usable by the OS.
> 
> Support for this address translation was introduced to the MCA subsystem
> with Zen1 systems. The code was later moved to the AMD64 EDAC module,
> since this was the only user of the code at the time.
> 
> However, there are uses for this translation outside of EDAC. The system
> physical address can be used in MCA for preemptive page offlining as done
> in some MCA notifier functions. Also, this translation is needed as the
> basis of similar functionality needed for some CXL configurations on AMD
> systems.
> 
> Introduce a common address translation library that can be used for
> multiple subsystems including MCA, EDAC, and CXL.
> 
> Include support for UMC normalized to system physical address
> translation for current CPU systems.
> 
> The Data Fabric Indirect register access offsets and one of the register
> fields were changed. Default to the current offsets and register field
> definition. And fallback to the older values if running on a "legacy"
> system.
> 
> Provide built-in code to facilitate the loading and unloading of the
> library module without affecting other modules or built-in code.
> 
> Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> ---

...

> +int get_address_map(struct addr_ctx *ctx)
> +{
> +	int ret = 0;

Nit: unneeded init

> +
> +	ret = get_address_map_common(ctx);
> +	if (ret)
> +		goto out;
> +
> +	ret = get_global_map_data(ctx);
> +	if (ret)
> +		goto out;
> +
> +	dump_address_map(&ctx->map);
> +
> +out:
> +	return ret;
> +}
> diff --git a/drivers/ras/amd/atl/reg_fields.h b/drivers/ras/amd/atl/reg_fields.h
> new file mode 100644
> index 000000000000..6aaa5093f42c
> --- /dev/null
> +++ b/drivers/ras/amd/atl/reg_fields.h
> @@ -0,0 +1,603 @@

...

> +static void get_num_maps(void)
> +{
> +	switch (df_cfg.rev) {
> +	case DF2:
> +	case DF3:
> +	case DF3p5:
> +		df_cfg.num_coh_st_maps	= 2;
> +		break;
> +	case DF4:
> +		df_cfg.num_coh_st_maps	= 4;
> +		break;

If 4 is the correct value in both cases, DF4 and DF4p5 cases could be 
merged.

CJ

> +	case DF4p5:
> +		df_cfg.num_coh_st_maps	= 4;
> +		break;
> +	default:
> +		atl_debug_on_bad_df_rev();
> +	}
> +}

...