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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b5e8bd1a2bsm17916359f8f.14.2025.07.16.04.57.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Jul 2025 04:57:26 -0700 (PDT) Date: Wed, 16 Jul 2025 12:57:25 +0100 From: David Laight To: Peter Zijlstra Cc: Lu Baolu , Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , Jason Gunthorpe , Jann Horn , Vasant Hegde , Dave Hansen , Alistair Popple , Uladzislau Rezki , Jean-Philippe Brucker , Andy Lutomirski , "Tested-by : Yi Lai" , iommu@lists.linux.dev, security@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 1/1] iommu/sva: Invalidate KVA range on kernel TLB flush Message-ID: <20250716125725.37aa3f38@pumpkin> In-Reply-To: <20250710155319.GK1613633@noisy.programming.kicks-ass.net> References: <20250709062800.651521-1-baolu.lu@linux.intel.com> <20250710135432.GO1613376@noisy.programming.kicks-ass.net> <20250710155319.GK1613633@noisy.programming.kicks-ass.net> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 10 Jul 2025 17:53:19 +0200 Peter Zijlstra wrote: > On Thu, Jul 10, 2025 at 03:54:32PM +0200, Peter Zijlstra wrote: > > > > @@ -132,8 +136,15 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm > > > if (ret) > > > goto out_free_domain; > > > domain->users = 1; > > > - list_add(&domain->next, &mm->iommu_mm->sva_domains); > > > > > > + if (list_empty(&iommu_mm->sva_domains)) { > > > + scoped_guard(spinlock_irqsave, &iommu_mms_lock) { > > > + if (list_empty(&iommu_sva_mms)) > > > + static_branch_enable(&iommu_sva_present); > > > + list_add(&iommu_mm->mm_list_elm, &iommu_sva_mms); > > > + } > > > + } > > > + list_add(&domain->next, &iommu_mm->sva_domains); > > > out: > > > refcount_set(&handle->users, 1); > > > mutex_unlock(&iommu_sva_lock); > > > @@ -175,6 +186,15 @@ void iommu_sva_unbind_device(struct iommu_sva *handle) > > > list_del(&domain->next); > > > iommu_domain_free(domain); > > > } > > > + > > > + if (list_empty(&iommu_mm->sva_domains)) { > > > + scoped_guard(spinlock_irqsave, &iommu_mms_lock) { > > > + list_del(&iommu_mm->mm_list_elm); > > > + if (list_empty(&iommu_sva_mms)) > > > + static_branch_disable(&iommu_sva_present); > > > + } > > > + } > > > + > > > mutex_unlock(&iommu_sva_lock); > > > kfree(handle); > > > } > > > > This seems an odd coding style choice; why the extra unneeded > > indentation? That is, what's wrong with: > > > > if (list_empty()) { > > guard(spinlock_irqsave)(&iommu_mms_lock); > > list_del(); > > if (list_empty() > > static_branch_disable(); > > } > > Well, for one, you can't do static_branch_{en,dis}able() from atomic > context... Aren't they also somewhat expensive - so you really want to use them for configuration options which pretty much don't change. David > > Was this ever tested? >