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[54.240.197.239]) by smtp.gmail.com with ESMTPSA id j6-20020a5d6046000000b0032fc5f5abafsm7034674wrt.96.2023.11.09.02.06.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Nov 2023 02:06:46 -0800 (PST) From: Paul Durrant X-Google-Original-From: Paul Durrant Message-ID: Date: Thu, 9 Nov 2023 10:06:40 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: paul@xen.org Subject: Re: [PATCH v7 00/11] KVM: xen: update shared_info and vcpu_info handling Content-Language: en-US To: David Woodhouse , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Paul Durrant , "H. Peter Anvin" , Borislav Petkov , Dave Hansen , Ingo Molnar , Paolo Bonzini , Sean Christopherson , Thomas Gleixner , x86@kernel.org References: <20231002095740.1472907-1-paul@xen.org> <6629b7f0b56e0fb2bad575a1d598cce26b1c6432.camel@infradead.org> <117d1e78e7277177236dabc616ade178fdc336fa.camel@infradead.org> Organization: Xen Project In-Reply-To: <117d1e78e7277177236dabc616ade178fdc336fa.camel@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/11/2023 10:02, David Woodhouse wrote: > On Thu, 2023-10-05 at 09:36 +0100, Paul Durrant wrote: >> On 05/10/2023 07:41, David Woodhouse wrote: >>> On Mon, 2023-10-02 at 09:57 +0000, Paul Durrant wrote: >>>> From: Paul Durrant >>>> >>>> The following text from the original cover letter still serves as an >>>> introduction to the series: >>>> >>>> "Currently we treat the shared_info page as guest memory and the VMM >>>> informs KVM of its location using a GFN. However it is not guest memory as >>>> such; it's an overlay page. So we pointlessly invalidate and re-cache a >>>> mapping to the *same page* of memory every time the guest requests that >>>> shared_info be mapped into its address space. Let's avoid doing that by >>>> modifying the pfncache code to allow activation using a fixed userspace HVA >>>> as well as a GPA." >>>> >>>> This version of the series is functionally the same as version 6. I have >>>> simply added David Woodhouse's R-b to patch 11 to indicate that he has >>>> now fully reviewed the series. >>> >>> Thanks. I believe Sean is probably waiting for us to stop going back >>> and forth, and for the dust to settle. So for the record: I think I'm >>> done heckling and this is ready to go in. >>> >>> Are you doing the QEMU patches or am I? >>> >> >> I'll do the QEMU changes, once the patches hit kvm/next. > > Note that I disabled migration support in QEMU for emulated Xen > guests. You might want that for testing, since the reason for this work > is to enable pause/serialize workflows. > > Migration does work all the way up to XenStore itself, and > https://gitlab.com/qemu-project/qemu/-/commit/766804b101d *was* tested > with migration enabled. There are also unit tests for XenStore > serialize/deserialize. > > I disabled it because the PV backends on the XenBus don't have > suspend/resume support. But a guest using other emulated net/disk > devices should still be able to suspend/resume OK if we just remove the > 'unmigratable' flag from xen_xenstore, I believe. Ok. Enabling suspend/resume for backends really ought not to be that hard. The main reason for this series was to enable pause for-for-memory-reconfiguration but I can look into suspend/resume/migrate once I've done the necessary re-work.