From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f173.google.com (mail-pf1-f173.google.com [209.85.210.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6A03511734 for ; Fri, 11 Aug 2023 17:14:04 +0000 (UTC) Received: by mail-pf1-f173.google.com with SMTP id d2e1a72fcca58-68783b2e40bso1695596b3a.3 for ; Fri, 11 Aug 2023 10:14:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1691774043; x=1692378843; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=bcJM0SLMxv8I13dY5TRlyJefXEA95JxGEoIyQSKlH3s=; b=KqNPrZIieuMXW+UgXUuHECVuGzp6DFkx3AYbo8xgXyKIzl+6R4MqT+E2phfEgUxYDS u5SrIMTZ0xlYbMTsBexIJMQZteqMFhQzd0kIP4j6LTJ39kgodtEXIHVUEdOTzOdLiGTR xK6w/uG8iTasuLVNR2msFgo+/IZ7iuBY9p5YcWmer1bGTNSDxjxGA4KJQkimxuT92uqG Flb9reLYIfU600rv825vz9iAh0HxtDZTfkxjheEdJQo7F6LIs0+SmJbwEKgB1muTIkK3 cySVwh4wWzmS3xD5X3QT2UER5Gl5IJ6LK0LaEa2s143Agjg1Qajxg8c4L0IvaVujlT5u /Itw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691774043; x=1692378843; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=bcJM0SLMxv8I13dY5TRlyJefXEA95JxGEoIyQSKlH3s=; b=BNDobEX++nXVnFONHj+IJ/XOxgzz/o1MKOqpL8yEllk4UOjszVKNRak2k7uwINw/aN Ttt9Dyk5pT2o9IA3LeJHf8g2HdOUto4r94TqsKs/JlSMn2N9w7P+icnQnYKu5boQA4KR 4XjDfYPUUBOcTvQcgZ64JHW/wN2Ykn3Uch0L3qUCE5qmV7bhfa3T37TlAEI+XUeUtTzX uE93XOH98JeCCUFIVEdfhzQYV/BharF2gwfbmKsqpOiIHwmqImY26UUmVYX/0Bi/bDRH qkyaIEnhP5F2Bj6Bf6MAcVx/tjkIBdcaHxsIiNXauZn+zVh59vh90jk1oTQM0OGC89gK Q9zw== X-Gm-Message-State: AOJu0YzI4K6W2utnyN1CrvokvapC9/uYGxf3R+zbhhv3E4bmM3cyplhn 7GzeH27fcWyyJQF3LhMGdLvcyQ== X-Google-Smtp-Source: AGHT+IGFh5YVV7fdqBpdV4FUhL2nsK7RQeaIPdvgZucjdKYKzxMNBjvOBrHSHNO3kBEv7zfbIObFlQ== X-Received: by 2002:a05:6a20:5497:b0:135:8a04:9045 with SMTP id i23-20020a056a20549700b001358a049045mr3266427pzk.1.1691774043466; Fri, 11 Aug 2023 10:14:03 -0700 (PDT) Received: from ziepe.ca ([206.223.160.26]) by smtp.gmail.com with ESMTPSA id r30-20020a63441e000000b0056001f43726sm3571605pga.92.2023.08.11.10.14.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Aug 2023 10:14:02 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1qUVi5-005Sth-As; Fri, 11 Aug 2023 14:14:01 -0300 Date: Fri, 11 Aug 2023 14:14:01 -0300 From: Jason Gunthorpe To: Baolu Lu Cc: Joerg Roedel , Will Deacon , Robin Murphy , Kevin Tian , Jean-Philippe Brucker , Nicolin Chen , Yi Liu , Jacob Pan , iommu@lists.linux.dev, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 12/12] iommu: Add helper to set iopf handler for domain Message-ID: References: <20230727054837.147050-1-baolu.lu@linux.intel.com> <20230727054837.147050-13-baolu.lu@linux.intel.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Aug 11, 2023 at 10:40:15AM +0800, Baolu Lu wrote: > On 2023/8/11 3:18, Jason Gunthorpe wrote: > > On Thu, Jul 27, 2023 at 01:48:37PM +0800, Lu Baolu wrote: > > > To avoid open code everywhere. > > > > > > Signed-off-by: Lu Baolu > > > --- > > > include/linux/iommu.h | 11 ++++++++++- > > > drivers/iommu/iommu.c | 20 ++++++++++++++++++-- > > > 2 files changed, 28 insertions(+), 3 deletions(-) > > > > Seems like overkill at this point.. > > > > Also, I think this is probably upside down. > > > > We want to create the domains as fault enabled in the first place. > > > > A fault enabled domain should never be attached to something that > > cannot support faults. It should also not support changing the fault > > handler while it exists. > > > > Thus at the creation point would be the time to supply the fault handler > > as part of requesting faulting. > > > > Taking an existing domain and making it faulting enabled is going to > > be really messy in all the corner cases. > > Yes. Agreed. > > > > > My advice (and Robin will probably hate me), is to define a new op: > > > > struct domain_alloc_paging_args { > > struct fault_handler *fault_handler; > > void *fault_data > > }; > > > > struct iommu_domain *domain_alloc_paging2(struct device *dev, struct > > domain_alloc_paging_args *args) > > > > The point would be to leave the majority of drivers using the > > simplified, core assisted, domain_alloc_paging() interface and they > > just don't have to touch any of this stuff at all. > > > > Obviously if handler is given then the domain will be initialized as > > faulting. > > Perhaps we also need an internal helper for iommu drivers to check the > iopf capability of the domain. Yeah, maybe. I've been mulling over this for a a bit here Robin suggested to wrap everything in a arg to domain_alloc and build a giant super multiplexor I don't really like that because it makes it quite complicated for the driver and multiplexor APIs are rarely good. So for simple drivers I like the 'domain_alloc_paging' as the only op they implement and it is obviously simple and hard to implement wrong. Most drivers would do this. We also need a: struct iommu_domain *domain_alloc_sva(struct device *dev, struct mm_struct *mm) So SVA can be fully setup at allocation time. SVA doesn't have any legal permutations so it can be kept simple. Then we need something to bundle: - Dirty tracking yes/no - The iommufd user space blob - Fault handling yes/no For complex drivers. So maybe we should just have a 3rd option // I'm a complex driver and many people checked that I implemented // this right: struct domain_alloc_args { struct device *dev; unsigned int flags; // For requesting dirty tracking // alloc_domain_user interface struct iommu_domain *parent; void *user_data; size_t user_len; // Faulting struct fault_handler *fault_handler; void *fault_data; }; struct iommu_domain *domain_alloc(struct domain_alloc_args *args); ? IDK, multiplexor APIs are rarely good, but maybe this is the right direction? Jason