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[70.31.27.79]) by smtp.gmail.com with ESMTPSA id s2-20020a05620a29c200b006ce40fbb8f6sm7649270qkp.21.2022.09.24.06.22.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 24 Sep 2022 06:22:34 -0700 (PDT) Date: Sat, 24 Sep 2022 09:22:32 -0400 From: Peter Xu To: Marc Zyngier Subject: Re: [PATCH 2/6] KVM: Add KVM_CAP_DIRTY_LOG_RING_ORDERED capability and config option Message-ID: References: <20220922170133.2617189-1-maz@kernel.org> <20220922170133.2617189-3-maz@kernel.org> <87czbmjhbh.wl-maz@kernel.org> <87edw1i290.wl-maz@kernel.org> <87czblhv2a.wl-maz@kernel.org> MIME-Version: 1.0 In-Reply-To: <87czblhv2a.wl-maz@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: kvm@vger.kernel.org, catalin.marinas@arm.com, andrew.jones@linux.dev, will@kernel.org, shan.gavin@gmail.com, bgardon@google.com, dmatlack@google.com, pbonzini@redhat.com, zhenyzha@redhat.com, shuah@kernel.org, kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Sat, Sep 24, 2022 at 12:26:53PM +0100, Marc Zyngier wrote: > On Sat, 24 Sep 2022 09:51:39 +0100, > Marc Zyngier wrote: > > > > On Fri, 23 Sep 2022 19:26:18 +0100, > > Peter Xu wrote: > > > > > > On Fri, Sep 23, 2022 at 03:28:34PM +0100, Marc Zyngier wrote: > > > > On Thu, 22 Sep 2022 22:48:19 +0100, > > > > Peter Xu wrote: > > > > > > > > > > On Thu, Sep 22, 2022 at 06:01:29PM +0100, Marc Zyngier wrote: > > > > > > In order to differenciate between architectures that require no extra > > > > > > synchronisation when accessing the dirty ring and those who do, > > > > > > add a new capability (KVM_CAP_DIRTY_LOG_RING_ORDERED) that identify > > > > > > the latter sort. TSO architectures can obviously advertise both, while > > > > > > relaxed architectures most only advertise the ORDERED version. > > > > > > > > > > > > Suggested-by: Paolo Bonzini > > > > > > Signed-off-by: Marc Zyngier > > > > > > --- > > > > > > include/linux/kvm_dirty_ring.h | 6 +++--- > > > > > > include/uapi/linux/kvm.h | 1 + > > > > > > virt/kvm/Kconfig | 14 ++++++++++++++ > > > > > > virt/kvm/Makefile.kvm | 2 +- > > > > > > virt/kvm/kvm_main.c | 11 +++++++++-- > > > > > > 5 files changed, 28 insertions(+), 6 deletions(-) > > > > > > > > > > > > diff --git a/include/linux/kvm_dirty_ring.h b/include/linux/kvm_dirty_ring.h > > > > > > index 906f899813dc..7a0c90ae9a3f 100644 > > > > > > --- a/include/linux/kvm_dirty_ring.h > > > > > > +++ b/include/linux/kvm_dirty_ring.h > > > > > > @@ -27,7 +27,7 @@ struct kvm_dirty_ring { > > > > > > int index; > > > > > > }; > > > > > > > > > > > > -#ifndef CONFIG_HAVE_KVM_DIRTY_RING > > > > > > +#ifndef CONFIG_HAVE_KVM_DIRTY_LOG > > > > > > > > > > s/LOG/LOG_RING/ according to the commit message? Or the name seems too > > > > > generic. > > > > > > > > The commit message talks about the capability, while the above is the > > > > config option. If you find the names inappropriate, feel free to > > > > suggest alternatives (for all I care, they could be called FOO, BAR > > > > and BAZ). > > > > > > The existing name from David looks better than the new one.. to me. > > > > I'm happy to bikeshed, but please spell it out for me. If we follow > > the current scheme, we need 3 configuration symbols (of which we > > already have one), and 2 capabilities (of which we already have one). I hope it's not bikeshedding. I normally don't comment on namings at all because many of them can be "bikeshedding" to me. But this one is so special because it directly collides with KVM_GET_DIRTY_LOG, which is other method of dirty tracking. > > > > Do you have any concrete proposal for those? > > In order to make some forward progress, I've reworked the series[1] > with another proposal for those: > > Config symbols: > > - HAVE_KVM_DIRTY_RING: > * mostly the same meaning as today > * not directly selected by any architecture > * doesn't expose any capability on its own > > - HAVE_KVM_DIRTY_RING_TSO: > * only for strongly ordered architectures > * selects HAVE_KVM_DIRTY_RING > * exposes KVM_CAP_DIRTY_LOG_RING > * selected by x86 > > - HAVE_KVM_DIRTY_RING_ACQ_REL: > * selects HAVE_KVM_DIRTY_RING > * exposes KVM_CAP_DIRTY_LOG_RING_ACQ_REL > * selected by arm64 and x86 > > Capabilities: > > - KVM_CAP_DIRTY_LOG_RING: the good old x86-specific stuff, advertised > when HAVE_KVM_DIRTY_RING_TSO is selected > > - KVM_CAP_DIRTY_LOG_RING_ACQ_REL: the new acquire/release semantics, > advertised when HAVE_KVM_DIRTY_RING_ACQ_REL is selected > > This significantly reduces the churn and makes things slightly more > explicit. This looks good to me, thanks. -- Peter Xu _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm