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[142.68.50.193]) by smtp.gmail.com with ESMTPSA id e2-20020ac845c2000000b003a5c6ad428asm6418411qto.92.2022.12.12.15.08.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Dec 2022 15:08:58 -0800 (PST) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1p4rur-008z7X-EE; Mon, 12 Dec 2022 19:08:57 -0400 Date: Mon, 12 Dec 2022 19:08:57 -0400 From: Jason Gunthorpe To: Alex Williamson Cc: Steven Sistare , "Tian, Kevin" , "kvm@vger.kernel.org" Subject: Re: [PATCH] vfio/type1: Cleanup remaining vaddr removal/update fragments Message-ID: References: <20221208094008.1b79dd59.alex.williamson@redhat.com> <20221209124212.672b7a9c.alex.williamson@redhat.com> <5f494e1f-536d-7225-e2c7-5ec9c993f13a@oracle.com> <20221209140120.667cb658.alex.williamson@redhat.com> <6914b4eb-cd82-0c3e-6637-c7922092ef11@oracle.com> <20221212085823.5d760656.alex.williamson@redhat.com> <8f29aad0-7378-ef7a-9ac5-f98b3054d5eb@oracle.com> <20221212142651.263dd6ae.alex.williamson@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221212142651.263dd6ae.alex.williamson@redhat.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Dec 12, 2022 at 02:26:51PM -0700, Alex Williamson wrote: > On Mon, 12 Dec 2022 15:59:11 -0500 > Steven Sistare wrote: > > > On 12/12/2022 10:58 AM, Alex Williamson wrote: > > > On Mon, 12 Dec 2022 09:17:54 -0400 > > > Jason Gunthorpe wrote: > > > > > >> On Sat, Dec 10, 2022 at 09:14:06AM -0500, Steven Sistare wrote: > > >> > > >>> Thank you for your thoughtful response. Rather than debate the degree of > > >>> of vulnerability, I propose an alternate solution. The technical crux of > > >>> the matter is support for mediated devices. > > >> > > >> I'm not sure I'm convinced about that. It is easy to make problematic > > >> situations with mdevs, but that doesn't mean other cases don't exist > > >> too eg what happens if userspace suspends and then immediately does > > >> something to trigger a domain attachment? Doesn't it still deadlock > > >> the kernel? > > > > > > The opportunity for that to deadlock isn't obvious to me, a replay > > > would be stalled waiting for invalid vaddrs, but this is essentially > > > the user deadlocking themselves. There's also code there to handle the > > > process getting killed while waiting, making it interruptible. Thanks, > > > > I will submit new patches tomorrow to exclude mdevs. Almost done. > > I've dropped the removal commits from my next branch in the interim. Woah, please don't do that - I already built and sent pull requests assuming this, there are conflicts. Why would we not revert everything from 6.2 - that is what we agreed to do? Jason