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X-CSE-ConnectionGUID: 4bwj58UVRM2htLkvGn6wdA== X-CSE-MsgGUID: ms39P4GSSOmQ3cz1XRqBYQ== X-IronPort-AV: E=McAfee;i="6800,10657,11514"; a="60453086" X-IronPort-AV: E=Sophos;i="6.17,268,1747724400"; d="scan'208";a="60453086" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Aug 2025 09:34:15 -0700 X-CSE-ConnectionGUID: 9IlwzfMvSPKiq37JcfswNw== X-CSE-MsgGUID: eR4LIcD7TVews0mh1gsSAA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.17,268,1747724400"; d="scan'208";a="170190193" Received: from kcaccard-desk.amr.corp.intel.com (HELO [10.125.110.154]) ([10.125.110.154]) by orviesa005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Aug 2025 09:34:13 -0700 Message-ID: <62d21545-9e75-41e3-89a3-f21dda15bf16@intel.com> Date: Wed, 6 Aug 2025 09:34:12 -0700 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/1] iommu/sva: Invalidate KVA range on kernel TLB flush To: Jason Gunthorpe Cc: Lu Baolu , Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , Jann Horn , Vasant Hegde , Alistair Popple , Peter Zijlstra , Uladzislau Rezki , Jean-Philippe Brucker , Andy Lutomirski , Yi Lai , iommu@lists.linux.dev, security@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20250806052505.3113108-1-baolu.lu@linux.intel.com> <20250806155223.GV184255@nvidia.com> <20250806160904.GX184255@nvidia.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/6/25 09:09, Jason Gunthorpe wrote: >>> >>> You can't do this approach without also pushing the pages to freed on >>> a list and defering the free till the work. This is broadly what the >>> normal mm user flow is doing.. >> FWIW, I think the simplest way to do this is to plop an unconditional >> schedule_work() in pte_free_kernel(). The work function will invalidate >> the IOTLBs and then free the page. >> >> Keep the schedule_work() unconditional to keep it simple. The >> schedule_work() is way cheaper than all the system-wide TLB invalidation >> IPIs that have to get sent as well. No need to add complexity to >> optimize out something that's in the noise already. > That works also, but now you have to allocate memory or you are > dead.. Is it OK these days, and safe in this code which seems a little > bit linked to memory management? > > The MM side avoided this by putting the list and the rcu_head in the > struct page. I don't think you need to allocate memory. A little static structure that uses the page->list and has a lock should do. Logically something like this: struct kernel_pgtable_work { struct list_head list; spinlock_t lock; struct work_struct work; } kernel_pte_work; pte_free_kernel() { struct page *page = ptdesc_magic(); guard(spinlock)(&kernel_pte_work.lock); list_add(&page->list, &kernel_pte_work.list); schedule_work(&kernel_pte_work.work); } work_func() { iommu_sva_invalidate_kva(); guard(spinlock)(&kernel_pte_work.lock); list_for_each_safe() { page = container_of(...); free_whatever(page); } } The only wrinkle is that pte_free_kernel() itself still has a pte and 'ptdesc', not a 'struct page'. But there is ptdesc->pt_list, which should be unused at this point, especially for non-pgd pages on x86. So, either go over to the 'struct page' earlier (maybe by open-coding pagetable_dtor_free()?), or just use the ptdesc.