From: "Michael S. Tsirkin" <mst@redhat.com>
To: Ani Sinha <ani.sinha@nutanix.com>
Cc: "Eduardo Habkost" <ehabkost@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"Aleksandar Markovic" <aleksandar.qemu.devel@gmail.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Ani Sinha" <ani@anisinha.ca>,
"Igor Mammedov" <imammedo@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Aurelien Jarno" <aurelien@aurel32.net>,
"Richard Henderson" <rth@twiddle.net>
Subject: Re: [PATCH V2] Add a new PIIX option to control PCI hot unplugging of devices on non-root buses
Date: Wed, 29 Apr 2020 06:15:41 -0400 [thread overview]
Message-ID: <20200429060230-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CEF52CB4-73FE-4D45-ACF7-440F7EC9AA1F@nutanix.com>
On Wed, Apr 29, 2020 at 09:14:26AM +0000, Ani Sinha wrote:
>
>
> > On Apr 29, 2020, at 2:26 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > Even if it seems to work for guests now, if we don't stick to emulating
> > capabilities that hardware interfaces provide we can never be sure it
> > will keep working.
>
> OS es use ACPI for PCI bridges: https://github.com/qemu/qemu/blob/master/docs/pcie.txt
> They use “_EJ0” to detect jot unplug capability: https://uefi.org/sites/default/files/resources/ACPI_3.pdf
>
> 6.3.3 _EJx (Eject) These control methods are optional and are supplied for devices that support a software-controlled VCRstyle ejection mechanism or that require an action be performed such as isolation of power/data lines before the device can be removed from the system. To support warm (system is in a sleep state) and hot (system is in S0) removal, an _EJx control method is listed for each sleep state from which the device supports removal, where x is the sleeping state supported. For example, _EJ0 indicates the device supports hot removal; _EJ1–EJ4 indicate the device supports warm removal.
Yes. So if there's no _EJx then it's reasonable to assume you can't
isolate the slot, and so no hot-plug will happen either.
>
> Note that “these control methods are optional” line. If the OS adheres to the spec, it should not expect them to exist all the time.
>
--
MST
next prev parent reply other threads:[~2020-04-29 10:17 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 10:16 [PATCH V2] Add a new PIIX option to control PCI hot unplugging of devices on non-root buses Ani Sinha
2020-04-28 10:20 ` Ani Sinha
2020-04-28 16:05 ` Michael S. Tsirkin
2020-04-28 16:09 ` Ani Sinha
2020-04-28 16:21 ` Michael S. Tsirkin
2020-04-28 16:40 ` Ani Sinha
2020-04-28 20:45 ` Michael S. Tsirkin
2020-04-29 0:58 ` Ani Sinha
2020-04-29 5:28 ` Michael S. Tsirkin
2020-04-29 5:59 ` Ani Sinha
2020-04-29 6:11 ` Ani Sinha
2020-04-29 6:52 ` Michael S. Tsirkin
2020-04-29 6:54 ` Ani Sinha
2020-04-29 6:57 ` Michael S. Tsirkin
2020-04-29 7:02 ` Ani Sinha
2020-04-29 7:38 ` Michael S. Tsirkin
2020-04-29 7:43 ` Ani Sinha
2020-04-29 8:09 ` Michael S. Tsirkin
2020-04-29 8:14 ` Ani Sinha
2020-04-29 8:56 ` Michael S. Tsirkin
2020-04-29 9:14 ` Ani Sinha
2020-04-29 9:18 ` Ani Sinha
2020-04-29 10:15 ` Michael S. Tsirkin [this message]
2020-04-29 10:20 ` Ani Sinha
2020-04-29 10:30 ` Michael S. Tsirkin
2020-04-29 10:37 ` Ani Sinha
2020-04-30 17:12 ` Ani Sinha
2020-04-28 16:28 ` Daniel P. Berrangé
2020-04-28 16:30 ` Michael S. Tsirkin
2020-04-28 16:33 ` Daniel P. Berrangé
2020-04-28 20:44 ` Michael S. Tsirkin
2020-05-11 18:53 ` Igor Mammedov
2020-05-12 5:26 ` Ani Sinha
2020-05-13 19:43 ` Igor Mammedov
2020-05-15 12:13 ` Ani Sinha
2020-05-20 9:43 ` Igor Mammedow
2020-05-20 9:47 ` Michael S. Tsirkin
2020-05-20 9:56 ` Igor Mammedow
2020-05-20 10:06 ` Daniel P. Berrangé
2020-05-20 11:29 ` Michael S. Tsirkin
2020-05-20 11:42 ` Daniel P. Berrangé
2020-05-20 11:44 ` Michael S. Tsirkin
2020-05-20 10:28 ` Michael S. Tsirkin
2020-05-20 11:05 ` Igor Mammedow
2020-05-20 11:23 ` Michael S. Tsirkin
2020-05-20 12:20 ` Igor Mammedow
2020-05-20 16:13 ` Michael S. Tsirkin
2020-05-21 7:32 ` Igor Mammedow
2020-05-21 10:07 ` Michael S. Tsirkin
2020-05-21 13:23 ` Igor Mammedov
2020-05-21 15:40 ` Laine Stump
2020-05-26 5:32 ` Ani Sinha
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