From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AFEB7386422 for ; Tue, 4 Aug 2026 02:48:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785811737; cv=none; b=PHmGXoqmQLl9xKRDmrUFs4wnnFhVkrIDJf2gCPSzigqXy25krqncopYspQu0HEHxTEqnELBwLRXaK6KgCSpZSagW8/e60AjcU9cgI+Zqyad1dnb5CxkKgB2nyAkBWMjtmK4jnFLQmUAVa8+fiuGi4H8ouh4glhJVeuD2FlkR01c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785811737; c=relaxed/simple; bh=bYxhmqmIFX9Vs3YJLdvrfZ/i13mZ7a4GJErjKqVa80A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OTVrFlO3buT6c9xr5fcOluwe+eMVXCfIBSFEaSnnB6RwBGTD8X2FPtAmMcruwYQ6uXRdN4ScGsMluIWdINYPsdR3dBQF6P2pA+dFOl6D7OmzUAGNw2Aa1ZJFJYeYZzEu45QEgg8n394maAy0LfwrnltBFM00pjfjy7Rup6f0opE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=YUUuK09o; arc=none smtp.client-ip=192.198.163.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="YUUuK09o" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1785811736; x=1817347736; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=bYxhmqmIFX9Vs3YJLdvrfZ/i13mZ7a4GJErjKqVa80A=; b=YUUuK09ojZOpD0odheKSquZzpIxjvLk1CiZBjVFLPMFAm+nIdBxWoWiL N5uYN4LAKQ/cUk8OGEMIzO970OhOeXZ7vmkUCkhyjg1sdMQyvGrDgI2KA nuK/quVVaLwvTO/FBKfIbXWd/KRw/rQV6/Hnr7NnHFFwVFXJtIwtgHhx0 EmgIOx99lUpQyGag99dnf2RvXHhkcTvTzJMnd3mBwkqNOHo8+JWs4LwLU Vso9MlsWSvYlKgG/m8LMNCoI+x7G2bl/8zgLo4JonyEQ6e/gjYT8JpTcM ttEs9vCGGYi+wK2cLxViR8F6IzNR1BdUXz1jsCYSfaOScvscHHme1Vb9v g==; X-CSE-ConnectionGUID: xLKy5WJ4RHWtfzD6B40W9Q== X-CSE-MsgGUID: IfoZomfGQcqFnNiX0E4Dxg== X-IronPort-AV: E=McAfee;i="6800,10657,11864"; a="86231338" X-IronPort-AV: E=Sophos;i="6.25,203,1779174000"; d="scan'208";a="86231338" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Aug 2026 19:48:55 -0700 X-CSE-ConnectionGUID: J48bjZ5VT/ev0XZHKw4CvQ== X-CSE-MsgGUID: ayQfe9fhQOGNf+DEnL7NQw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,203,1779174000"; d="scan'208";a="259587576" Received: from allen-box.sh.intel.com ([10.239.159.52]) by orviesa006.jf.intel.com with ESMTP; 03 Aug 2026 19:48:53 -0700 From: Lu Baolu To: Joerg Roedel Cc: ZhaoJinming , Kevin Tian , Dmitry Antipov , Guanghui Feng , Li RongQing , Desnes Nunes , iommu@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH 14/20] iommu/vt-d: Cache max domain ID to avoid redundant calculation Date: Tue, 4 Aug 2026 10:37:08 +0800 Message-ID: <20260804023714.3080506-15-baolu.lu@linux.intel.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260804023714.3080506-1-baolu.lu@linux.intel.com> References: <20260804023714.3080506-1-baolu.lu@linux.intel.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The cap_ndoms() helper calculates the maximum available domain ID from the value of capability register, which can be inefficient if called repeatedly. Cache the maximum supported domain ID in max_domain_id field during initialization to avoid redundant calls to cap_ndoms() throughout the IOMMU driver. No functionality change. Signed-off-by: Lu Baolu Signed-off-by: Xu Yilun Reviewed-by: Kevin Tian --- drivers/iommu/intel/iommu.h | 1 + drivers/iommu/intel/dmar.c | 1 + drivers/iommu/intel/iommu.c | 10 +++++----- 3 files changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h index 656cd311ed9a..c00f44db0020 100644 --- a/drivers/iommu/intel/iommu.h +++ b/drivers/iommu/intel/iommu.h @@ -700,6 +700,7 @@ struct intel_iommu { /* mutex to protect domain_ida */ struct mutex did_lock; struct ida domain_ida; /* domain id allocator */ + unsigned long max_domain_id; unsigned long *copied_tables; /* bitmap of copied tables */ spinlock_t lock; /* protect context, domain ids */ struct root_entry *root_entry; /* virtual address */ diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c index 33bfaeafa7c6..c854173f6be9 100644 --- a/drivers/iommu/intel/dmar.c +++ b/drivers/iommu/intel/dmar.c @@ -1174,6 +1174,7 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd) spin_lock_init(&iommu->lock); ida_init(&iommu->domain_ida); mutex_init(&iommu->did_lock); + iommu->max_domain_id = cap_ndoms(iommu->cap); ver = readl(iommu->reg + DMAR_VER_REG); pr_info("%s: reg_base_addr %llx ver %d:%d cap %llx ecap %llx\n", diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index a996b72aca57..5ea584b76f77 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -1047,7 +1047,7 @@ int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu) } num = ida_alloc_range(&iommu->domain_ida, IDA_START_DID, - cap_ndoms(iommu->cap) - 1, GFP_KERNEL); + iommu->max_domain_id - 1, GFP_KERNEL); if (num < 0) { pr_err("%s: No free domain ids\n", iommu->name); goto err_unlock; @@ -1111,7 +1111,7 @@ static void copied_context_tear_down(struct intel_iommu *iommu, did_old = context_domain_id(context); context_clear_entry(context); - if (did_old < cap_ndoms(iommu->cap)) { + if (did_old < iommu->max_domain_id) { iommu->flush.flush_context(iommu, did_old, PCI_DEVID(bus, devfn), DMA_CCMD_MASK_NOBIT, @@ -1511,7 +1511,7 @@ static int copy_context_table(struct intel_iommu *iommu, continue; did = context_domain_id(&ce); - if (did >= 0 && did < cap_ndoms(iommu->cap)) + if (did >= 0 && did < iommu->max_domain_id) ida_alloc_range(&iommu->domain_ida, did, did, GFP_KERNEL); set_context_copied(iommu, bus, devfn); @@ -2431,7 +2431,7 @@ static ssize_t domains_supported_show(struct device *dev, struct device_attribute *attr, char *buf) { struct intel_iommu *iommu = dev_to_intel_iommu(dev); - return sysfs_emit(buf, "%ld\n", cap_ndoms(iommu->cap)); + return sysfs_emit(buf, "%ld\n", iommu->max_domain_id); } static DEVICE_ATTR_RO(domains_supported); @@ -2442,7 +2442,7 @@ static ssize_t domains_used_show(struct device *dev, unsigned int count = 0; int id; - for (id = 0; id < cap_ndoms(iommu->cap); id++) + for (id = 0; id < iommu->max_domain_id; id++) if (ida_exists(&iommu->domain_ida, id)) count++; -- 2.43.0