From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f44.google.com (mail-ej1-f44.google.com [209.85.218.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AFD564204F for ; Sun, 14 Apr 2024 16:25:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713111909; cv=none; b=rxGdJkT3dH1OPFv4rQQ5/VsdLFqE1s9/bEfpF5anXj1WcHGqtOkovhcUz9jChI0JJS9loCy4TmZPb34QscnfbHt/+BPvh7hhcZT4CX/0yLrLssvoCBFLHNyu6VswE5m7ac4DWXO9Gdf8ieJKLks2kPEvujFRuNmf/in8YdC6RiU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713111909; c=relaxed/simple; bh=x9zY+X01BxCJYs60384+4AxqPsLSpqAW3M0zfApyxdc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=T11rTHhVNAbzXPbQWm7u34iSTE7mFx93uXqaEAQiVquWFUR6uY0Its671BmGiQEWe08kwdR7AURYtIACCceZOuKQZ2CVWzP4S7H0cc4EyK9UEfFFgpm3zgrOtPcL6ClO3AJONXvWzFWVTk7At91H+rKdpvEHjSMI5E6Jrsxm8Uc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=m7/JtsVu; arc=none smtp.client-ip=209.85.218.44 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="m7/JtsVu" Received: by mail-ej1-f44.google.com with SMTP id a640c23a62f3a-a44ad785a44so278278166b.3 for ; Sun, 14 Apr 2024 09:25:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1713111906; x=1713716706; darn=lists.linux.dev; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=OVsG3JCtQo4tlTQt5Af4gG7a1SS2UAv4W4YMU6rXC8Y=; b=m7/JtsVuP6aFYhO5G5uCAB0TgLsn5kFNmh3D35+Lzbw4Lfd3L8cN9ss5EM5yQ5Dp71 gIwyuW3QmENijNiMVs07/QCU2pqGqJhD1lRrsTLZGRJVIyLTE5zY6NmIbkRpCXNnLt0Y 226LVvU+atM+CctL7punxDAugZHLJjlNm+f3j18qZ+78dtD67T4gw5JCAc0tu4z5WX1M RCnMJJfdle6NGWCfa1QkJXgFZ90N0HRhiSxuG0TnnqSj+Uwr3fm8iLoBacwGHsmDGGlJ LTRQ7q58c2M3ZTG/WG50lHxlzD3nK8zN41UfyyMuVyTfaavUgOQ3YmwxlYkFUJu2STuy aLdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713111906; x=1713716706; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=OVsG3JCtQo4tlTQt5Af4gG7a1SS2UAv4W4YMU6rXC8Y=; b=m8IHb1gYUAbRQAR9gJ8zUWQC4pOD56tBqjZw4IAOdSMNoucesekeEp3nXBwtuEGsej hTWDFq8cMzWCXY2toSbX1rxfRSx6R2nPNUiMFcv2RKAE/nq7TROf9Q7MT/g8PHZcKag9 3/R7m8G7rQHXDjfEbjwQgZkS4SiKIMLYIUDvjtJTt/ic7Yv+bvzZuLxFoodzUNb4TAyv dowtf7MjipaYpDNMSdlVJBLjuIYvyBXq8ZkPE4PBmEIbav0MrIscG6nk0F/dU8L8XGBh niaaXfrwM1gTpb18GMuNgiLD+sLi00efNoD+FagOl1/j2xjYpyfVyZHmtuXKR0A8YDh8 /vzA== X-Gm-Message-State: AOJu0Yz9xK0MogZxrrkMKVpt7T+7mk9f4CivYhT2BVoUcBx/Uwn/U7zC dh5DWpnvecBWboIGx1Ptypuxo8IXLodVEGtKywe7qoNpmMSfXEp9Hq82mQ== X-Google-Smtp-Source: AGHT+IH9g+mcCrogr0CIRidhtrDFP5KjqkCIgE/JGUqj2zc3wRYfBX9PYIONiFkO0uvOTfch9T1big== X-Received: by 2002:a17:906:2932:b0:a51:969e:ba0 with SMTP id v18-20020a170906293200b00a51969e0ba0mr4631415ejd.44.1713111905479; Sun, 14 Apr 2024 09:25:05 -0700 (PDT) Received: from localhost.localdomain ([46.248.82.114]) by smtp.gmail.com with ESMTPSA id b18-20020a1709063f9200b00a523cf3293fsm2920181ejj.59.2024.04.14.09.25.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 14 Apr 2024 09:25:04 -0700 (PDT) From: Uros Bizjak To: iommu@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Uros Bizjak , David Woodhouse , Lu Baolu , Joerg Roedel , Will Deacon , Robin Murphy Subject: [PATCH] iommu/intel: Use try_cmpxchg64{,_local}() in iommu.c Date: Sun, 14 Apr 2024 18:23:11 +0200 Message-ID: <20240414162454.49584-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.42.0 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Replace this pattern in iommu.c: cmpxchg64{,_local}(*ptr, 0, new) != 0 ... with the simpler and faster: !try_cmpxchg64{,_local}(*ptr, &tmp, new) The x86 CMPXCHG instruction returns success in the ZF flag, so this change saves a compare after the CMPXCHG. No functional change intended. Signed-off-by: Uros Bizjak Cc: David Woodhouse Cc: Lu Baolu Cc: Joerg Roedel Cc: Will Deacon Cc: Robin Murphy --- drivers/iommu/intel/iommu.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 50eb9aed47cc..311073494f50 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -865,7 +865,7 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain, break; if (!dma_pte_present(pte)) { - uint64_t pteval; + uint64_t pteval, tmp; tmp_page = alloc_pgtable_page(domain->nid, gfp); @@ -877,7 +877,8 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain, if (domain->use_first_level) pteval |= DMA_FL_PTE_XD | DMA_FL_PTE_US | DMA_FL_PTE_ACCESS; - if (cmpxchg64(&pte->val, 0ULL, pteval)) + tmp = 0ULL; + if (!try_cmpxchg64(&pte->val, &tmp, pteval)) /* Someone else set it while we were thinking; use theirs. */ free_pgtable_page(tmp_page); else @@ -2128,8 +2129,8 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn, /* We don't need lock here, nobody else * touches the iova range */ - tmp = cmpxchg64_local(&pte->val, 0ULL, pteval); - if (tmp) { + tmp = 0ULL; + if (!try_cmpxchg64_local(&pte->val, &tmp, pteval)) { static int dumps = 5; pr_crit("ERROR: DMA PTE for vPFN 0x%lx already set (to %llx not %llx)\n", iov_pfn, tmp, (unsigned long long)pteval); -- 2.42.0