From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 78FA31F959 for ; Fri, 6 Oct 2023 13:45:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BD49811FB; Fri, 6 Oct 2023 06:46:29 -0700 (PDT) Received: from [10.57.66.230] (unknown [10.57.66.230]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7DEAD3F641; Fri, 6 Oct 2023 06:45:48 -0700 (PDT) Message-ID: <14555232-bc81-496d-bb06-7a7502f26568@arm.com> Date: Fri, 6 Oct 2023 14:45:47 +0100 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/7] iommu/arm-smmu: Reorganize arm_smmu_domain_add_master() Content-Language: en-GB To: Jason Gunthorpe Cc: iommu@lists.linux.dev, Joerg Roedel , linux-arm-kernel@lists.infradead.org, Will Deacon , Lu Baolu , Heiko Stuebner , Joerg Roedel , Jerry Snitselaar , Marek Szyprowski , Nicolin Chen , Niklas Schnelle , Steven Price References: <1-v1-cf5846854f51+6db3f-smmu_newapi_jgg@nvidia.com> <20231006123001.GO682044@nvidia.com> From: Robin Murphy In-Reply-To: <20231006123001.GO682044@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2023-10-06 13:30, Jason Gunthorpe wrote: > On Fri, Oct 06, 2023 at 01:05:03PM +0100, Robin Murphy wrote: >> On 2023-10-05 19:28, Jason Gunthorpe wrote: >>> Make arm_smmu_domain_add_master() not use the smmu_domain to detect the >>> s2cr configuration, instead pass it in as a parameter. It always returns >>> zero so make it return void. >> >> It doesn't follow that a function named arm_smmu_domain_() should >> not operate on an arm_smmu_domain... I think this is the point to rename it >> to something like arm_smmu_master_install_s2crs() to reflect that what it's >> actually doing by now is a lot less than it did 10 years ago. > > heh, yes, I did not notice > >>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c >>> index d6d1a2a55cc069..7f33363719f4ac 100644 >>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c >>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c >>> @@ -1081,21 +1081,14 @@ static void arm_smmu_master_free_smes(struct arm_smmu_master_cfg *cfg, >>> mutex_unlock(&smmu->stream_map_mutex); >>> } >>> -static int arm_smmu_domain_add_master(struct arm_smmu_domain *smmu_domain, >>> - struct arm_smmu_master_cfg *cfg, >>> - struct iommu_fwspec *fwspec) >>> +static void arm_smmu_domain_add_master(struct arm_smmu_device *smmu, >> >> We already have the SMMU device in cfg->smmu, no need to pass it twice. > > Sure, but the caller also already has it on its stack.. Stack? Caller? Not in my build ;) 00000000000040b8 : ... smmu = cfg->smmu; 410c: f94002d3 ldr x19, [x22] ... smmu_domain->smmu = smmu; 4268: f90002f3 str x19, [x23] ... struct arm_smmu_s2cr *s2cr = smmu->s2crs; 44e0: f9403a79 ldr x25, [x19, #112] ... ret = arm_smmu_domain_add_master(smmu_domain, cfg, fwspec); 4544: 5280001c mov w28, #0x0 ... Even if the compiler didn't inline the heck out of an easy inlining candidate, this is hardly a critical hot path where an extra load would make any difference, so the only thing this code needs optimising for is readability, or Donald Knuth will be sad :( Thanks, Robin.