From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Re: [RFC PATCH 0/5] madvise MADV_DOEXEC Date: Tue, 4 Aug 2020 12:13:16 +0100 Message-ID: <20200804111316.GE23808@casper.infradead.org> References: <20200730171251.GI23808@casper.infradead.org> <63a7404c-e4f6-a82e-257b-217585b0277f@oracle.com> <20200730174956.GK23808@casper.infradead.org> <87y2n03brx.fsf@x220.int.ebiederm.org> <689d6348-6029-5396-8de7-a26bc3c017e5@oracle.com> <877dufvje9.fsf@x220.int.ebiederm.org> <1596469370.29091.13.camel@HansenPartnership.com> <9371b8272fd84280ae40b409b260bab3@AcuMS.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55440 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730016AbgHDLO6 (ORCPT ); Tue, 4 Aug 2020 07:14:58 -0400 Content-Disposition: inline In-Reply-To: <9371b8272fd84280ae40b409b260bab3@AcuMS.aculab.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Laight Cc: 'James Bottomley' , "Eric W. Biederman" , Steven Sistare , Anthony Yznaga , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-arch@vger.kernel.org" , "mhocko@kernel.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "x86@kernel.org" , "hpa@zytor.com" , "viro@zeniv.linux.org.uk" , "akpm@linux-foundation.org" , "arnd@arndb.de" On Tue, Aug 04, 2020 at 08:44:42AM +0000, David Laight wrote: > From: James Bottomley > > Sent: 03 August 2020 16:43 > > > > On Mon, 2020-08-03 at 10:28 -0500, Eric W. Biederman wrote: > > [...] > > > What is wrong with live migration between one qemu process and > > > another qemu process on the same machine not work for this use case? > > > > > > Just reusing live migration would seem to be the simplest path of > > > all, as the code is already implemented. Further if something goes > > > wrong with the live migration you can fallback to the existing > > > process. With exec there is no fallback if the new version does not > > > properly support the handoff protocol of the old version. > > > > Actually, could I ask this another way: the other patch set you sent to > > the KVM list was to snapshot the VM to a PKRAM capsule preserved across > > kexec using zero copy for extremely fast save/restore. The original > > idea was to use this as part of a CRIU based snapshot, kexec to new > > system, restore. However, why can't you do a local snapshot, restart > > qemu, restore using the PKRAM capsule to achieve exactly the same as > > MADV_DOEXEC does but using a system that's easy to reason about? It > > may be slightly slower, but I think we're still talking milliseconds. > > > I've had another idea (that is probably impossible...). > What about a 'reverse mmap' operation. > Something that creates an fd whose contents are a chunk of the > processes address space. http://www.wil.cx/~willy/linux/sileby.html From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 4 Aug 2020 12:13:16 +0100 From: Matthew Wilcox Subject: Re: [RFC PATCH 0/5] madvise MADV_DOEXEC Message-ID: <20200804111316.GE23808@casper.infradead.org> References: <20200730171251.GI23808@casper.infradead.org> <63a7404c-e4f6-a82e-257b-217585b0277f@oracle.com> <20200730174956.GK23808@casper.infradead.org> <87y2n03brx.fsf@x220.int.ebiederm.org> <689d6348-6029-5396-8de7-a26bc3c017e5@oracle.com> <877dufvje9.fsf@x220.int.ebiederm.org> <1596469370.29091.13.camel@HansenPartnership.com> <9371b8272fd84280ae40b409b260bab3@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9371b8272fd84280ae40b409b260bab3@AcuMS.aculab.com> Sender: owner-linux-mm@kvack.org To: David Laight Cc: 'James Bottomley' , "Eric W. Biederman" , Steven Sistare , Anthony Yznaga , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-arch@vger.kernel.org" , "mhocko@kernel.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "x86@kernel.org" , "hpa@zytor.com" , "viro@zeniv.linux.org.uk" , "akpm@linux-foundation.org" , "arnd@arndb.de" , "keescook@chromium.org" , "gerg@linux-m68k.org" , "ktkhai@virtuozzo.com" , "christian.brauner@ubuntu.com" , "peterz@infradead.org" , "esyr@redhat.com" , "jgg@ziepe.ca" , "christian@kellner.me" , "areber@redhat.com" , "cyphar@cyphar.com" List-ID: Message-ID: <20200804111316.DuypSRvd_jVYvyHv0wCnqwhCtK_yGAfoQnlK1cTDZvA@z> On Tue, Aug 04, 2020 at 08:44:42AM +0000, David Laight wrote: > From: James Bottomley > > Sent: 03 August 2020 16:43 > > > > On Mon, 2020-08-03 at 10:28 -0500, Eric W. Biederman wrote: > > [...] > > > What is wrong with live migration between one qemu process and > > > another qemu process on the same machine not work for this use case? > > > > > > Just reusing live migration would seem to be the simplest path of > > > all, as the code is already implemented. Further if something goes > > > wrong with the live migration you can fallback to the existing > > > process. With exec there is no fallback if the new version does not > > > properly support the handoff protocol of the old version. > > > > Actually, could I ask this another way: the other patch set you sent to > > the KVM list was to snapshot the VM to a PKRAM capsule preserved across > > kexec using zero copy for extremely fast save/restore. The original > > idea was to use this as part of a CRIU based snapshot, kexec to new > > system, restore. However, why can't you do a local snapshot, restart > > qemu, restore using the PKRAM capsule to achieve exactly the same as > > MADV_DOEXEC does but using a system that's easy to reason about? It > > may be slightly slower, but I think we're still talking milliseconds. > > > I've had another idea (that is probably impossible...). > What about a 'reverse mmap' operation. > Something that creates an fd whose contents are a chunk of the > processes address space. http://www.wil.cx/~willy/linux/sileby.html