Re: [PATCH] arm64: Subscribe Microsoft Azure Cobalt 100 to ARM Neoverse N2 errata

From: Oliver Upton
Date: Mon Feb 12 2024 - 18:44:44 EST


Hi Easwar,

On Mon, Feb 12, 2024 at 11:29:06PM +0000, Easwar Hariharan wrote:
> Add the MIDR value of Microsoft Azure Cobalt 100, which is a Microsoft
> implemented CPU based on r0p0 of the ARM Neoverse N2 CPU, and therefore
> suffers from all the same errata.

Can you comment at all on where one might find this MIDR? That is, does
your hypervisor report the native MIDR of the implementation or does it
repaint it as an Arm Neoverse N2 (0x410FD490)?

> diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
> index 7c7493cb571f..a632a7514e55 100644
> --- a/arch/arm64/include/asm/cputype.h
> +++ b/arch/arm64/include/asm/cputype.h
> @@ -61,6 +61,7 @@
> #define ARM_CPU_IMP_HISI 0x48
> #define ARM_CPU_IMP_APPLE 0x61
> #define ARM_CPU_IMP_AMPERE 0xC0
> +#define ARM_CPU_IMP_MICROSOFT 0x6D
>
> #define ARM_CPU_PART_AEM_V8 0xD0F
> #define ARM_CPU_PART_FOUNDATION 0xD00
> @@ -135,6 +136,8 @@
>
> #define AMPERE_CPU_PART_AMPERE1 0xAC3
>
> +#define MSFT_CPU_PART_AZURE_COBALT_100 0xD49 /* Based on r0p0 of ARM Neoverse N2 */
> +
> #define MIDR_CORTEX_A53 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A53)
> #define MIDR_CORTEX_A57 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A57)
> #define MIDR_CORTEX_A72 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A72)
> @@ -193,6 +196,7 @@
> #define MIDR_APPLE_M2_BLIZZARD_MAX MIDR_CPU_MODEL(ARM_CPU_IMP_APPLE, APPLE_CPU_PART_M2_BLIZZARD_MAX)
> #define MIDR_APPLE_M2_AVALANCHE_MAX MIDR_CPU_MODEL(ARM_CPU_IMP_APPLE, APPLE_CPU_PART_M2_AVALANCHE_MAX)
> #define MIDR_AMPERE1 MIDR_CPU_MODEL(ARM_CPU_IMP_AMPERE, AMPERE_CPU_PART_AMPERE1)
> +#define MIDR_MICROSOFT_AZURE_COBALT_100 MIDR_CPU_MODEL(ARM_CPU_IMP_MICROSOFT, MSFT_CPU_PART_AZURE_COBALT_100)

nitpick: consistently use the abbreviated 'MSFT' for all the definitions
you're adding.

--
Thanks,
Oliver