From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 AA585334714; Mon, 18 Aug 2025 14:10:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755526235; cv=none; b=Mv+rzc856WzZJB/Y7YX9WDJ/bAoYS0ZU1T/4kJj4qz/3VWw4t/ZSrzTeACXcpmq4TfHa53XLxVYyhzIwJA15ALEQamukrpO/VC2F3qEngdxwP/5UY4y+5RMHZ3UegMIUJXvqLgeC8Uya5OPgxYogYLmQApqhtVAVa4h4olRWor8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755526235; c=relaxed/simple; bh=yFA/RtPgmF6GYMtgY+Sa/z40O+qQ9AkWSYPUKr1nlVw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=n90siI6psJJlZfwVvxUJ2ozzd4+KVwNuOG7uDue7M83eNEJlCVVuf2/pjxiG0TxnvcnscRQZIX1/SRjUJE01+qYFyTgLrQNx3rWI4IcdjrIDYTUFoTMGFppb7jDnqSh351DpyySaQb1SgDf7Jo3/8BTc8n+FR5L0C1p937aGL2U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=fZPzD6lO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="fZPzD6lO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7233C4CEEB; Mon, 18 Aug 2025 14:10:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755526235; bh=yFA/RtPgmF6GYMtgY+Sa/z40O+qQ9AkWSYPUKr1nlVw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fZPzD6lOpSCcOT1LHEkHSKkYL79Z0ADUYygRBJRJ36Klv8gRR7oMrkzfARCiXjNeh 4z/7dVq3eVbefdlfhlmcnpj2FFmMwrNcESdeb+zph17TjlaKPR78A0KNHYZ4NFJdVs FcVDESK3U8i44B6C1i9uXLACMkA3D+IoLjNy375w= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ioanna Alifieraki , Lu Baolu , Kevin Tian , Will Deacon Subject: [PATCH 6.16 497/570] iommu/vt-d: Optimize iotlb_sync_map for non-caching/non-RWBF modes Date: Mon, 18 Aug 2025 14:48:04 +0200 Message-ID: <20250818124525.013074711@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250818124505.781598737@linuxfoundation.org> References: <20250818124505.781598737@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lu Baolu commit 12724ce3fe1a3d8f30d56e48b4f272d8860d1970 upstream. The iotlb_sync_map iommu ops allows drivers to perform necessary cache flushes when new mappings are established. For the Intel iommu driver, this callback specifically serves two purposes: - To flush caches when a second-stage page table is attached to a device whose iommu is operating in caching mode (CAP_REG.CM==1). - To explicitly flush internal write buffers to ensure updates to memory- resident remapping structures are visible to hardware (CAP_REG.RWBF==1). However, in scenarios where neither caching mode nor the RWBF flag is active, the cache_tag_flush_range_np() helper, which is called in the iotlb_sync_map path, effectively becomes a no-op. Despite being a no-op, cache_tag_flush_range_np() involves iterating through all cache tags of the iommu's attached to the domain, protected by a spinlock. This unnecessary execution path introduces overhead, leading to a measurable I/O performance regression. On systems with NVMes under the same bridge, performance was observed to drop from approximately ~6150 MiB/s down to ~4985 MiB/s. Introduce a flag in the dmar_domain structure. This flag will only be set when iotlb_sync_map is required (i.e., when CM or RWBF is set). The cache_tag_flush_range_np() is called only for domains where this flag is set. This flag, once set, is immutable, given that there won't be mixed configurations in real-world scenarios where some IOMMUs in a system operate in caching mode while others do not. Theoretically, the immutability of this flag does not impact functionality. Reported-by: Ioanna Alifieraki Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2115738 Link: https://lore.kernel.org/r/20250701171154.52435-1-ioanna-maria.alifieraki@canonical.com Fixes: 129dab6e1286 ("iommu/vt-d: Use cache_tag_flush_range_np() in iotlb_sync_map") Cc: stable@vger.kernel.org Signed-off-by: Lu Baolu Reviewed-by: Kevin Tian Link: https://lore.kernel.org/r/20250703031545.3378602-1-baolu.lu@linux.intel.com Link: https://lore.kernel.org/r/20250714045028.958850-3-baolu.lu@linux.intel.com Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- drivers/iommu/intel/iommu.c | 19 ++++++++++++++++++- drivers/iommu/intel/iommu.h | 3 +++ 2 files changed, 21 insertions(+), 1 deletion(-) --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -1795,6 +1795,18 @@ static int domain_setup_first_level(stru (pgd_t *)pgd, flags, old); } +static bool domain_need_iotlb_sync_map(struct dmar_domain *domain, + struct intel_iommu *iommu) +{ + if (cap_caching_mode(iommu->cap) && !domain->use_first_level) + return true; + + if (rwbf_quirk || cap_rwbf(iommu->cap)) + return true; + + return false; +} + static int dmar_domain_attach_device(struct dmar_domain *domain, struct device *dev) { @@ -1832,6 +1844,8 @@ static int dmar_domain_attach_device(str if (ret) goto out_block_translation; + domain->iotlb_sync_map |= domain_need_iotlb_sync_map(domain, iommu); + return 0; out_block_translation: @@ -3953,7 +3967,10 @@ static bool risky_device(struct pci_dev static int intel_iommu_iotlb_sync_map(struct iommu_domain *domain, unsigned long iova, size_t size) { - cache_tag_flush_range_np(to_dmar_domain(domain), iova, iova + size - 1); + struct dmar_domain *dmar_domain = to_dmar_domain(domain); + + if (dmar_domain->iotlb_sync_map) + cache_tag_flush_range_np(dmar_domain, iova, iova + size - 1); return 0; } --- a/drivers/iommu/intel/iommu.h +++ b/drivers/iommu/intel/iommu.h @@ -614,6 +614,9 @@ struct dmar_domain { u8 has_mappings:1; /* Has mappings configured through * iommu_map() interface. */ + u8 iotlb_sync_map:1; /* Need to flush IOTLB cache or write + * buffer when creating mappings. + */ spinlock_t lock; /* Protect device tracking lists */ struct list_head devices; /* all devices' list */