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From: Ben Horgan <ben.horgan@arm.com>
To: will@kernel.org
Cc: james.morse@arm.com, fenghuay@nvidia.com,
	linux-arm-kernel@lists.infradead.org, andre.przywara@arm.com,
	gshan@redhat.com, tan.shaopeng@jp.fujitsu.com,
	sdonthineni@nvidia.com, jonathan.cameron@oss.qualcomm.com
Subject: Re: [PATCH 6/6] arm_mpam: Apply T241-MPAM-6 to 63-bit counters
Date: Sat, 1 Aug 2026 01:23:57 +0100	[thread overview]
Message-ID: <0fca2908-e8eb-4842-9a9b-a876fa459e02@arm.com> (raw)
In-Reply-To: <20260731175243.904730-7-ben.horgan@arm.com>

Hi Will,

On 7/31/26 18:52, Ben Horgan wrote:
> From: Shanker Donthineni <sdonthineni@nvidia.com>
> 
> T241-MPAM-6 causes all MBWU counter formats to count 64-byte
> requests instead of bytes. Commit dc48eb1ff27c excluded the 63-bit
> MSMON_MBWU_LWD format while scaling the shorter counters. Systems
> selecting the preferred 63-bit counter consequently report bandwidth
> values that are 64 times too small.
> 
> Apply the scale to both the sampled value and overflow correction for
> the 63-bit format. Unsigned arithmetic retains modulo-u64 behavior
> when the scaled counter range exceeds u64.
> 
> Fixes: dc48eb1ff27c ("arm_mpam: Add workaround for T241-MPAM-6")
> Link: https://lore.kernel.org/lkml/20240816131432.993859-1-sdonthineni@nvidia.com/
> Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
> Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
> Tested-by: Fenghua Yu <fenghuay@nvidia.com>
> Reviewed-by: Ben Horgan <ben.horgan@arm.com>
Should have put this before, sorry.

For handling the patch,

Signed-off-by: Ben Horgan <ben.horgan@arm.com>


      reply	other threads:[~2026-08-01  0:24 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-31 17:52 MPAM changes for v7.3 Ben Horgan
2026-07-31 17:52 ` [PATCH 1/6] arm_mpam: resctrl: Pick classes for use as MBM counters Ben Horgan
2026-07-31 17:52 ` [PATCH 2/6] arm_mpam: resctrl: Pre-allocate assignable monitors Ben Horgan
2026-07-31 17:52 ` [PATCH 3/6] arm_mpam: resctrl: Add resctrl_arch_config_cntr() for ABMC use Ben Horgan
2026-07-31 17:52 ` [PATCH 4/6] arm_mpam: resctrl: Add resctrl_arch_cntr_read() & resctrl_arch_reset_cntr() Ben Horgan
2026-07-31 17:52 ` [PATCH 5/6] arm64: mpam: Add memory bandwidth usage (MBWU) documentation Ben Horgan
2026-07-31 17:52 ` [PATCH 6/6] arm_mpam: Apply T241-MPAM-6 to 63-bit counters Ben Horgan
2026-08-01  0:23   ` Ben Horgan [this message]

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