From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.15]) (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 6EE36313E3D for ; Fri, 19 Sep 2025 14:22:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758291765; cv=none; b=N7bd4YyAFgBWXgD1z5I5JDNWjmUzaxKn4uR56ulDnJazqBcROYPPQNiZ3XP4Brm3QKGk24mQeoW0L1JYL16nIaQr1Jr9ye79t01ny7zjh9VbebcvH/l3ASQyPUbQwGxb5r40TFJYOzGBIEQyQtdVZk5qclcn9EH3Vy+qvT4NQh0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758291765; c=relaxed/simple; bh=i94V1+cgCGxA8RfxduxqkCM4Li64xgqL9iS8N+4yG0c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZtsDjZL2ff91cx8BFh7ik85xqryjuhvWaPBkmQ7xNH9fbY+T6bVM/XUWJvjEenRH18l5EHH73o6HQCirZCy/kFfRL1UgkFbuM//fHdA5VlZT8MbXueqjoGLdqMA90RtLQu2+XUxH3Xrgec02Ff+rEkTC4P80xmrpB6XI/OaqumE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=M5pUtYQD; arc=none smtp.client-ip=192.198.163.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="M5pUtYQD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1758291763; x=1789827763; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=i94V1+cgCGxA8RfxduxqkCM4Li64xgqL9iS8N+4yG0c=; b=M5pUtYQDkb64rpLhQVu85p3K9VkWUB6e5S/1oOTPFLoCUV0WXcimhn3U VrokK1dxea0jZX/EzV+aFDJrLXUlHB6/FDG7g+XwMAS7V0dKdU5O9UXFX jL3f2KZzrn2mSyQruisXIlPX0bBVeGdfKHtCpPDlykOb0cMx9TsVgFxAc Vf6JYYdeIE+2HixUCiRyQshzxTHii0Qmo+yaqO0yJKA9XwDL5/kV4f0rz Yp+dUCR206SnmFhqhTuGrR16qPOGDtSvqWbvMx39bnv1OphOTaMm+yBR4 i82xu3xl3MhUujeFFg3f7M30JyxD6xfGH05GiX/aucJ1oPqxfZc7uQC3g Q==; X-CSE-ConnectionGUID: 7xFcIjjJSpy0SIVp3bJzew== X-CSE-MsgGUID: i3GqyS0BTgq95WO6m1ZC0A== X-IronPort-AV: E=McAfee;i="6800,10657,11557"; a="60750540" X-IronPort-AV: E=Sophos;i="6.18,278,1751266800"; d="scan'208";a="60750540" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Sep 2025 07:22:38 -0700 X-CSE-ConnectionGUID: qrarD7YET/CWTLpnRKt2Ww== X-CSE-MsgGUID: cxmqiS8MRoGxAqMgP5sXiw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,278,1751266800"; d="scan'208";a="176655027" Received: from dwillia2-desk.jf.intel.com ([10.88.27.145]) by fmviesa010.fm.intel.com with ESMTP; 19 Sep 2025 07:22:38 -0700 From: Dan Williams To: linux-coco@lists.linux.dev, linux-pci@vger.kernel.org Cc: xin@zytor.com, chao.gao@intel.com, Lu Baolu Subject: [RFC PATCH 12/27] iommu/vt-d: Cache max domain ID to avoid redundant calculation Date: Fri, 19 Sep 2025 07:22:21 -0700 Message-ID: <20250919142237.418648-13-dan.j.williams@intel.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250919142237.418648-1-dan.j.williams@intel.com> References: <20250919142237.418648-1-dan.j.williams@intel.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Lu Baolu 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: Dan Williams --- drivers/iommu/intel/dmar.c | 1 + drivers/iommu/intel/iommu.c | 10 +++++----- drivers/iommu/intel/iommu.h | 1 + 3 files changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c index ec975c73cfe6..a54934c0536f 100644 --- a/drivers/iommu/intel/dmar.c +++ b/drivers/iommu/intel/dmar.c @@ -1099,6 +1099,7 @@ 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 9c3ab9d9f69a..9b02007ef831 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -1356,7 +1356,7 @@ 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; @@ -1420,7 +1420,7 @@ 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, @@ -1981,7 +1981,7 @@ 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); @@ -2897,7 +2897,7 @@ 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); @@ -2908,7 +2908,7 @@ 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++; diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h index d09b92871659..d16b1a51c6d6 100644 --- a/drivers/iommu/intel/iommu.h +++ b/drivers/iommu/intel/iommu.h @@ -727,6 +727,7 @@ 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 */ -- 2.51.0