linux-kernel - Re: [PATCH] iommu/arm-smmu-v3: Stop pre-zeroing batch commands

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Date:   Fri, 13 Aug 2021 15:33:47 +0100
From:   Will Deacon <will@...nel.org>
To:     robin.murphy@....com, John Garry <john.garry@...wei.com>
Cc:     catalin.marinas@....com, kernel-team@...roid.com,
        Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, thunder.leizhen@...wei.com,
        joro@...tes.org, linuxarm@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/arm-smmu-v3: Stop pre-zeroing batch commands

On Wed, 11 Aug 2021 23:49:26 +0800, John Garry wrote:
> Pre-zeroing the batched commands structure is inefficient, as individual
> commands are zeroed later in arm_smmu_cmdq_build_cmd(). The size is quite
> large and commonly most commands won't even be used:
> 
> 	struct arm_smmu_cmdq_batch cmds = {};
> 345c:	52800001 	mov	w1, #0x0                   	// #0
> 3460:	d2808102 	mov	x2, #0x408                 	// #1032
> 3464:	910143a0 	add	x0, x29, #0x50
> 3468:	94000000 	bl	0 <memset>
> 
> [...]

Applied to will (for-joerg/arm-smmu/updates), thanks!

[1/1] iommu/arm-smmu-v3: Stop pre-zeroing batch commands
      https://git.kernel.org/will/c/fac956710ab0

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev