ACK: [PATCH] mtrr: check memory type above 4GB on AMD platforms

[ivanhu]

On 1/8/19 3:14 AM, Alex Hung wrote:
> On AMD platforms, Tom2ForceMemTypeWB in MSR SYS_CFG (C001_0010)
> specifies the memory type above 4GB. If Tom2ForceMemTypeWB is set,
> memory above 4GB will be write-back instead of any other types
> (usually "uncached").
>
> More information can be found in AMD's PPR document:
> http://support.amd.com/TechDocs/54945_PPR_Family_17h_Models_00h-0Fh.pdf
>
> Signed-off-by: Alex Hung <alex.hung at canonical.com>
> ---
>  src/bios/mtrr/mtrr.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/src/bios/mtrr/mtrr.c b/src/bios/mtrr/mtrr.c
> index a614ffbb..53d1a807 100644
> --- a/src/bios/mtrr/mtrr.c
> +++ b/src/bios/mtrr/mtrr.c
> @@ -50,8 +50,10 @@ static fwts_cpuinfo_x86 *fwts_cpuinfo;
>  #define UNKNOWN		0x0080
>  
>  #define MTRR_DEF_TYPE_MSR	0x2FF
> +#define AMD_SYS_CFG_MSR		0xC0010010
>  
>  static	uint64_t mtrr_default;
> +static	bool amd_Tom2ForceMemTypeWB = false;
>  
>  struct mtrr_entry {
>  	uint8_t  reg;
> @@ -184,6 +186,17 @@ static int get_mtrrs(void)
>  
>  static int get_default_mtrr(fwts_framework *fw)
>  {
> +	uint64_t amd_sys_conf;
> +
> +	/* Get the default memory type of memory between 4GB and second top of
> +	 * memory (TOM2) - i.e. is it write back (WB)
> +	 */
> +	if (strstr(fwts_cpuinfo->vendor_id, "AMD")) {
> +		if (fwts_cpu_readmsr(fw, 0, AMD_SYS_CFG_MSR, &amd_sys_conf) == FWTS_OK)
> +			if (amd_sys_conf | 0x200000)
> +				amd_Tom2ForceMemTypeWB = true;
> +	}
> +
>  	if (fwts_cpu_readmsr(fw, 0, MTRR_DEF_TYPE_MSR, &mtrr_default) == FWTS_OK) {
>  		switch (mtrr_default & 0xFF) {
>  			case 0:
> @@ -216,6 +229,12 @@ static int cache_types(uint64_t start, uint64_t end)
>  	struct mtrr_entry *entry;
>  	int type = 0;
>  
> +	/* On AMD platforms, Tom2ForceMemTypeWB overwrites other memory types */
> +	if (amd_Tom2ForceMemTypeWB && start >= 0x100000000) {
> +		type = WRITE_BACK;
> +		return type;
> +	}
> +
>  	fwts_list_foreach(item, mtrr_list) {
>  		entry = fwts_list_data(struct mtrr_entry*, item);
>  


Acked-by: Ivan Hu <ivan.hu at canonical.com>