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From: Sadanand Warrier <sadanandwarrier@gmail.com>
To: Greg KH <greg@kroah.com>
Cc: Kernelnewbies@kernelnewbies.org
Subject: Re: PCIe hotplug
Date: Thu, 13 Feb 2020 14:50:52 -0500
Message-ID: <CADJuq2xo_3ZsEnk=SWNk3gEnXwNTMwbci1oJdtSdL+viHzMvRw@mail.gmail.com> (raw)
In-Reply-To: <20200213174846.GA3688355@kroah.com>

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Thank you Greg.
About the last one , it's been a while but I wasn't sure whether Linux was
going to do its own enumeration.
Of course it's best to take advantage of all the stuff done by UEFI ,
padding etc.

S

On Thu, 13 Feb 2020 at 12:48, Greg KH <greg@kroah.com> wrote:

> On Thu, Feb 13, 2020 at 12:40:59PM -0500, Sadanand Warrier wrote:
> > Hi
> >    I had  question about PCIe hotplug. We have hardware that is connected
> > to the host by means of two PCIe switches. i.e. the host sees a PCIe
> switch
> > connected to one of its buses and on the far side of that switch another
> > PCIe switch which has a PCIe device.
> >    It is possible that this device does not train its host facing PCIe
> > links before the server enumerates down its PCI bus and reaches those
> > links. It is also possible the PCIe switch to which the device is
> attached
> > has not been able to train its own links before server enumeration.
> >   Is PCIe hotplug built to work on schemes like this? Let us assume that
> > the hardware has been designed to trasmit a presence signal once the
> links
> > are trained but this could happen after the server enumeration?
>
> Look at the PCIe hotplug spec, it should answer all of your questions
> about this.
>
> >   Incidentally does the server take advantage of the BIOS/UEFI
> enumeration?
>
> Yes, of course, how else would the kernel be able to enumerate PCI
> devices?  :)
>
> thanks,
>
> greg k-h
>

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<div dir="ltr"><div>Thank you Greg.</div><div>About the last one , it&#39;s been a while but I wasn&#39;t sure whether Linux was going to do its own enumeration.</div><div>Of course it&#39;s best to take advantage of all the stuff done by UEFI , padding etc.</div><div><br></div><div>S</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, 13 Feb 2020 at 12:48, Greg KH &lt;<a href="mailto:greg@kroah.com">greg@kroah.com</a>&gt; wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On Thu, Feb 13, 2020 at 12:40:59PM -0500, Sadanand Warrier wrote:<br>
&gt; Hi<br>
&gt;    I had  question about PCIe hotplug. We have hardware that is connected<br>
&gt; to the host by means of two PCIe switches. i.e. the host sees a PCIe switch<br>
&gt; connected to one of its buses and on the far side of that switch another<br>
&gt; PCIe switch which has a PCIe device.<br>
&gt;    It is possible that this device does not train its host facing PCIe<br>
&gt; links before the server enumerates down its PCI bus and reaches those<br>
&gt; links. It is also possible the PCIe switch to which the device is attached<br>
&gt; has not been able to train its own links before server enumeration.<br>
&gt;   Is PCIe hotplug built to work on schemes like this? Let us assume that<br>
&gt; the hardware has been designed to trasmit a presence signal once the links<br>
&gt; are trained but this could happen after the server enumeration?<br>
<br>
Look at the PCIe hotplug spec, it should answer all of your questions<br>
about this.<br>
<br>
&gt;   Incidentally does the server take advantage of the BIOS/UEFI enumeration?<br>
<br>
Yes, of course, how else would the kernel be able to enumerate PCI<br>
devices?  :)<br>
<br>
thanks,<br>
<br>
greg k-h<br>
</blockquote></div></div>

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Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-13 17:40 Sadanand Warrier
2020-02-13 17:48 ` Greg KH
2020-02-13 19:50   ` Sadanand Warrier [this message]

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