Hi Mark,

quoted

+HWCAP3_MTE_FAR

quoted

+    Functionality implied by ID_AA64PFR2_EL1.MTEFAR == 0b0001.
+Applications should interpret the values of these bits based on
+the support for the 'mte_far' hwcap. If the support is not present,
+the values of these bits should be considered as undefined otherwise valid.

The constant is HWCAP3_MTE_FAR and the cpuinfo is mtefar:

+     [KERNEL_HWCAP_MTE_FAR]          = "mtefar",

The reference to the hwcap should probably be one of these, I'd go for
HWCAP3_MTE_FAR since it says hwcap.

Just for confirmation. so change to "mtefar" -> "mte_far"
Am I missing?


--  
Sincerely,
Yeoreum Yun




________________________________________
From: Mark Brown
Sent: Wednesday, June 11, 2025 12:43
To: Yeo Reum Yun
Cc: Catalin Marinas; pcc@google.com; will@kernel.org; Anshuman Khandual; Joey Gouly; Yury Khrustalev; maz@kernel.org; oliver.upton@linux.dev; frederic@kernel.org; akpm@linux-foundation.org; surenb@google.com; linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; linux-doc@vger.kernel.org
Subject: Re: [PATCH v6 2/9] arm64: report address tag when FEAT_MTE_TAGGED_FAR is supported


On Wed, Jun 11, 2025 at 10:41:00AM +0100, Yeoreum Yun wrote:

+HWCAP3_MTE_FAR

+    Functionality implied by ID_AA64PFR2_EL1.MTEFAR == 0b0001.

+Applications should interpret the values of these bits based on

+the support for the 'mte_far' hwcap. If the support is not present,

+the values of these bits should be considered as undefined otherwise valid.

The constant is HWCAP3_MTE_FAR and the cpuinfo is mtefar:

+     [KERNEL_HWCAP_MTE_FAR]          = "mtefar",

The reference to the hwcap should probably be one of these, I'd go for

HWCAP3_MTE_FAR since it says hwcap.

quoted

       /*
        * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN
        * for tag check faults. Set them to corresponding bits in the untagged
-      * address.
+      * address if ARM64_MTE_FAR isn't supported.
+      * Otherwise, bits 63:60 of FAR_EL1 are KNOWN.

Should this say UNKNOWN?

I think KNOWN is corret since this is Otherwise case (when MET_FAR is supported).

Thanks.