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[109.64.41.91]) by smtp.gmail.com with ESMTPSA id b2sm3618141wrm.30.2020.05.20.09.13.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2020 09:13:38 -0700 (PDT) Date: Wed, 20 May 2020 12:13:35 -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: <20200520121043-mutt-send-email-mst@kernel.org> References: <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> <20200520060645-mutt-send-email-mst@kernel.org> <20200520130547.7ac568b8@nas.mammed.net> <20200520072055-mutt-send-email-mst@kernel.org> <20200520142012.5394b2f6@nas.mammed.net> MIME-Version: 1.0 In-Reply-To: <20200520142012.5394b2f6@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=207.211.31.120; envelope-from=mst@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/20 01:34:51 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_H3=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 02:20:12PM +0200, Igor Mammedow wrote: > On Wed, 20 May 2020 07:23:21 -0400 > "Michael S. Tsirkin" wrote: > > > On Wed, May 20, 2020 at 01:05:47PM +0200, Igor Mammedow wrote: > > > On Wed, 20 May 2020 06:28:37 -0400 > > > "Michael S. Tsirkin" wrote: > > > > > > > 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? > > > it probably won't work with native SHPC hotplug (which looks to be > > > incomplete in QEMU anyway), but it should work with ACPI and per > > > port PCIE hotplugs. > > > In case of SHPC, we probably should be able to cleanly error out > > > with 'unsupported' reason if "hotpluggable" conflicts with bridge > > > policy. > > > > "Try it and see if it works" is somewhat problematic from management > > POV since there's a never ending stream of new things they would have > > to try. If this approach is taken, we'd have to try to loop in some > > people from libvirt and see what's their take. > to clarify, we are talking here about bridges to conventional > PCI with native SHPC hotplug semantics wrt mgmt and > potential pcidevice.hotpluggable property. > (the later should work fine in ACPI and PCIE hoptlug cases). > > currently by default pci bridges have property shpc=off, so mgmt > should know that deals with PCI bridge and has to enable SHPC > on bridge explicitly, Wait a second does that actually affect hotplug with ACPI too? > in which case it could probably be taught that > using conflicting hotpluggable for device attached to bridge and shpc > values is wrong thing. > If that's not it, then I'm not sure what kind of discovery you are > talking about. -- MST