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X-CSE-ConnectionGUID: I6EknQSiTvSk8lsRP0wvzQ== X-CSE-MsgGUID: e1ylIafpQAaoJH6ECmYrIQ== X-IronPort-AV: E=McAfee;i="6800,10657,11493"; a="72546673" X-IronPort-AV: E=Sophos;i="6.16,317,1744095600"; d="scan'208";a="72546673" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by fmvoesa102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Jul 2025 18:49:49 -0700 X-CSE-ConnectionGUID: kq5cbfU1QmKl0pu+6mUnXA== X-CSE-MsgGUID: tC5/M5KKReCe0iYKi2flUQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,317,1744095600"; d="scan'208";a="158367440" Received: from allen-sbox.sh.intel.com (HELO [10.239.159.30]) ([10.239.159.30]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Jul 2025 18:49:45 -0700 Message-ID: Date: Thu, 17 Jul 2025 09:47:52 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/1] iommu/sva: Invalidate KVA range on kernel TLB flush To: David Laight , Peter Zijlstra Cc: 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 References: <20250709062800.651521-1-baolu.lu@linux.intel.com> <20250710135432.GO1613376@noisy.programming.kicks-ass.net> <20250710155319.GK1613633@noisy.programming.kicks-ass.net> <20250716125725.37aa3f38@pumpkin> Content-Language: en-US From: Baolu Lu In-Reply-To: <20250716125725.37aa3f38@pumpkin> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/16/25 19:57, David Laight wrote: > 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. Yeah! Fair enough. Thanks, baolu