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[70.31.27.79]) by smtp.gmail.com with ESMTPSA id s2-20020a05620a29c200b006ce40fbb8f6sm11386754qkp.21.2022.09.26.08.17.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Sep 2022 08:17:15 -0700 (PDT) Date: Mon, 26 Sep 2022 11:17:14 -0400 From: Peter Xu To: Igor Mammedov Cc: qemu-devel@nongnu.org, Jason Wang , "Michael S . Tsirkin" , Paolo Bonzini , David Woodhouse , Claudio Fontana Subject: Re: [PATCH] Revert "intel_iommu: Fix irqchip / X2APIC configuration checks" Message-ID: References: <20220921161227.57259-1-peterx@redhat.com> <20220922154617.57d1a1fb@redhat.com> <20220923102034.6579b66c@redhat.com> <20220923104159.39576159@redhat.com> <20220926113311.417316b7@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220926113311.417316b7@redhat.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Sep 26, 2022 at 11:33:11AM +0200, Igor Mammedov wrote: > On Fri, 23 Sep 2022 21:27:08 -0400 > Peter Xu wrote: > > > On Fri, Sep 23, 2022 at 06:03:44PM -0400, Peter Xu wrote: > > > On Fri, Sep 23, 2022 at 10:41:59AM +0200, Igor Mammedov wrote: > > > > It's worth putting history excavation with explanation what is broken and why > > > > compat stuff is being ignored in the patch. > > > > > > Makes sense, I'll amend the commit message and repost. Thanks, > > > > There's actually one way to slightly remedy this single case, mostly for > > any QEMU 7.1.0 user with -smp <=8 and the intel iommu (as 77250171bdc02 is > > merged only in 7.1.0). > > > > We can have one compact parameter x-eim-enable-kvm-x2apic, setting it "on" > > by default, "off" for 7.1, and "on" for 7.0-. > > > > I'm not very sure whether that'll worth it. Any thoughts? > > How it (enabling x2apic API) would affect kvm/guests running with 8 or less CPUs > and with intel iommu + remapping? It's more from the guest ABI level, but indeed at least from what I see so far <=8 CPUs are fine. I'll keep the patch short, thanks. -- Peter Xu