linux-kernel - Re: [PATCH 2/3] iommu/vt-d: Use try_cmpxchg64() in intel_pasid_get

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Message-ID: <44d4013d-5c25-40ba-a599-91eee6d50a8c@linux.intel.com>
Date: Fri, 24 May 2024 09:09:11 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Uros Bizjak <ubizjak@...il.com>, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Cc: baolu.lu@...ux.intel.com, David Woodhouse <dwmw2@...radead.org>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH 2/3] iommu/vt-d: Use try_cmpxchg64() in
 intel_pasid_get_entry()

On 5/22/24 4:26 PM, Uros Bizjak wrote:
> Use try_cmpxchg64() instead of cmpxchg64 (*ptr, old, new) != old in
> intel_pasid_get_entry().  cmpxchg returns success in ZF flag, so
> this change saves a compare after cmpxchg (and related move
> instruction in front of cmpxchg).
> 
> Signed-off-by: Uros Bizjak<ubizjak@...il.com>
> Cc: David Woodhouse<dwmw2@...radead.org>
> Cc: Lu Baolu<baolu.lu@...ux.intel.com>
> Cc: Joerg Roedel<joro@...tes.org>
> Cc: Will Deacon<will@...nel.org>
> Cc: Robin Murphy<robin.murphy@....com>
> ---
>   drivers/iommu/intel/pasid.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)

Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>

Best regards,
baolu