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[109.64.41.91]) by smtp.gmail.com with ESMTPSA id t129sm3043661wmg.27.2020.05.20.03.28.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2020 03:28:40 -0700 (PDT) Date: Wed, 20 May 2020 06:28:37 -0400 From: "Michael S. Tsirkin" To: Igor Mammedow Subject: Re: [PATCH V2] Add a new PIIX option to control PCI hot unplugging of devices on non-root buses Message-ID: <20200520060645-mutt-send-email-mst@kernel.org> References: <1588069012-211196-1-git-send-email-ani.sinha@nutanix.com> <20200511205352.05ff541a@redhat.com> <9941B800-BBEF-4DF8-BEE0-EC39D2A20D98@nutanix.com> <20200513214312.0dfa4752@redhat.com> <7FF83CE8-F25A-4458-80A7-EAA6296EF175@nutanix.com> <20200520114354.1982cb63@nas.mammed.net> <20200520054714-mutt-send-email-mst@kernel.org> <20200520115626.6a2a2355@nas.mammed.net> MIME-Version: 1.0 In-Reply-To: <20200520115626.6a2a2355@nas.mammed.net> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=mst@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/20 02:22:41 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Ani Sinha , Eduardo Habkost , Julia Suvorova , "qemu-devel@nongnu.org" , Aleksandar Markovic , Ani Sinha , Paolo Bonzini , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Aurelien Jarno , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, May 20, 2020 at 11:56:26AM +0200, Igor Mammedow wrote: > On Wed, 20 May 2020 05:47:53 -0400 > "Michael S. Tsirkin" wrote: > > > On Wed, May 20, 2020 at 11:43:54AM +0200, Igor Mammedow wrote: > > > On Fri, 15 May 2020 12:13:53 +0000 > > > Ani Sinha wrote: > > > > > > > > On May 14, 2020, at 1:13 AM, Igor Mammedov > > > > > wrote: > > > > >> > > > > >> > > > > >>> Will following hack work for you? > > > > >>> possible permutations > > > > >>> 1) ACPI hotplug everywhere > > > > >>> -global PIIX4_PM.acpi-pci-hotplug=on -global > > > > >>> PIIX4_PM.acpi-pci-hotplug-with-bridge-support=on -device > > > > >>> pci-bridge,chassis_nr=1,shpc=doesnt_matter -device > > > > >>> e1000,bus=pci.1,addr=01,id=netdev1 > > > > >>> > > > > >>> 2) No hotplug at all > > > > >>> -global PIIX4_PM.acpi-pci-hotplug=off -global > > > > >>> PIIX4_PM.acpi-pci-hotplug-with-bridge-support=on -device > > > > >>> pci-bridge,chassis_nr=1,shpc=off -device > > > > >>> e1000,bus=pci.1,addr=01,id=netdev1 > > > > >>> > > > > >>> -global PIIX4_PM.acpi-pci-hotplug=off -global > > > > >>> PIIX4_PM.acpi-pci-hotplug-with-bridge-support=off -device > > > > >>> pci-bridge,chassis_nr=1,shpc=doesnt_matter -device > > > > >>> e1000,bus=pci.1,addr=01,id=netdev1 > > > > >> > > > > >> Given that my patch is not acceptable, I’d prefer the > > > > >> following in the order of preference: > > > > >> > > > > >> (a) Have an option to disable hot ejection of PCI-PCI bridge so > > > > >> that Windows does not even show this HW in the “safely remove > > > > >> HW” option. If we can do this then from OS perspective the GUI > > > > >> options will be same as what is available with PCIE/q35 - none > > > > >> of the devices will be hot ejectable if the hot plug option is > > > > >> turned off from the PCIE slots where devices are plugged into. > > > > >> I looked at the code. It seems to manipulate ACPI tables of > > > > >> the empty slots of the root bus where no devices are attached > > > > >> (see comment "/* add hotplug slots for non present devices */ > > > > >> “). For cold plugged bridges, it recurses down to scan the > > > > >> slots of the bridge. Is it possible to disable hot plug for > > > > >> the slot to which the bridge is attached? > > > > > > > > > > I don't think it's possible to have per slot hotplug on > > > > > conventional PCI hardware. it's per bridge property. > > > > > > > > We add the AMLs per empty slot though. When the pic bridge is > > > > attached, we do nothing, just recurse into the bridge slots. That > > > > is what I was asking, if it was possible to just disable the AMLs > > > > or use some tricks to say that this particular slot is not > > > > hotpluggable. I am not sure why Windows is trying to eject the > > > > PCI bridge and failing. Maybe something related to this comment? > > > > > > > > > > > > /* When hotplug for bridges is enabled, bridges are > > > > > > > > * described in ACPI separately (see build_pci_bus_end). > > > > > > > > * In this case they aren't themselves hot-pluggable. > > > > > > > > * Hotplugged bridges *are* hot-pluggable. > > > > */ > > > > > > thinking some more on this topic, it seems that with ACPI hotplug we > > > already have implicit non-hotpluggble slot (slot with bridge) while > > > the rest are staying hotpluggable. > > > > > > So my question is: if it's acceptable to add > > > 'PCIDevice::hotpluggable" property to all PCI devices so that user > > > / libvirt could set it to false in case they do not want > > > coldplugged device be considered as hotpluggable? (this way other > > > devices could be treated the same way as bridges) > > > > > > [...] > > > > > > I think Julia already posted a patch adding this to downstream pcie > > bridges. Adding this to pci slots sounds like a reasonable thing. > Question was more about external interface, were we do not have ports > as separate devices with conventional PCI. The only knob we have is a > a PCI device, where we have a property to turn on/off hotplug. ex: > -device e1000,hotpluggable=off > and if libvirt would be able to use it It would make sense but is it practical to add the capability is added in a generic way to all bridges and hosts? If not how do users probe for presence of the capability? -- MST