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[109.64.41.91]) by smtp.gmail.com with ESMTPSA id 5sm2490616wmd.19.2020.05.20.02.47.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2020 02:47:56 -0700 (PDT) Date: Wed, 20 May 2020 05:47:53 -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: <20200520054714-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> MIME-Version: 1.0 In-Reply-To: <20200520114354.1982cb63@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=205.139.110.120; envelope-from=mst@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/19 22:48:02 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_H4=0.001, RCVD_IN_MSPIKE_WL=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 11:43:54AM +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. -- MST