Re: Notes from PCI Passthrough design discussion at Xen Summit

From: Manish Jaggi <mjaggi@caviumnetworks.com>
To: "Julien Grall" <julien.grall@linaro.org>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Cc: edgar.iglesias@xilinx.com,
	Stefano Stabellini <sstabellini@kernel.org>,
	Jan Beulich <JBeulich@suse.com>, Wei Chen <Wei.Chen@arm.com>,
	Steve Capper <Steve.Capper@arm.com>,
	Andre Przywara <andre.przywara@arm.com>,
	manish.jaggi@caviumnetworks.com,
	Punit Agrawal <punit.agrawal@arm.com>,
	vikrams@qti.qualcomm.com, okaya@qti.qualcomm.com, "Goel,
	Sameer" <sgoel@qti.qualcomm.com>,
	xen-devel <xen-devel@lists.xenproject.org>,
	Dave P Martin <Dave.Martin@arm.com>,
	Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
Subject: Re: Notes from PCI Passthrough design discussion at Xen Summit
Date: Thu, 20 Jul 2017 16:30:30 +0530	[thread overview]
Message-ID: <b8113dbf-e01e-1834-366c-53376a23e0be@caviumnetworks.com> (raw)
In-Reply-To: <0739d17a-ab20-be39-76b5-ce4d36ed0037@linaro.org>

HI Julien,

On 7/20/2017 4:11 PM, Julien Grall wrote:
>
>
> On 20/07/17 10:32, Manish Jaggi wrote:
>> Hi Roger,
>>
>> On 7/20/2017 1:54 PM, Roger Pau Monné wrote:
>>> On Thu, Jul 20, 2017 at 09:24:36AM +0530, Manish Jaggi wrote:
>>>> Hi Punit,
>>>>
>>>> On 7/19/2017 8:11 PM, Punit Agrawal wrote:
>>>>> I took some notes for the PCI Passthrough design discussion at Xen
>>>>> Summit. Due to the wide range of topics covered, the notes got 
>>>>> sparser
>>>>> towards the end of the session. I've tried to attribute names against
>>>>> comments but have very likely got things mixed up. Apologies in
>>>>> advance.
>>>> Was curious if any discussions happened on the RC Emu (config space
>>>> emulation) as per slide 18
>>>> https://schd.ws/hosted_files/xendeveloperanddesignsummit2017/76/slides.pdf 
>>>>
>>>>
>>> Part of this is already posted on the list (ATM for x86 only) but the
>>> PCI specification (and therefore the config space emulation) is not
>>> tied to any arch:
>>>
>>> https://lists.xenproject.org/archives/html/xen-devel/2017-06/msg03698.html 
>>>
>>>
>> From the summary, I have a  questions on
>> "
>>  - Roger: Registering config space with Xen before device discovery
>>   will allow the hypervisor to set access traps for certain
>>  functionality as appropriate"
>>
>> Traps will do emulation or something else ?
>>  Is the config space emulation only for DomU or it for Dom0 as well ?
>> Slide 18 shows only for DomU ?
>
> My slides are not meant to be read without the talk. In this 
> particular case, this is only explaining how passthrough will work for 
> DomU.
>
Thanks for clarification.
Ah ok, The single slide created confusion, It would be nice if you have 
added one more describing dom0 config access. I will wait for the video 
to get posted.
> Roger series is at the moment focusing on emulating a fully ECAM 
> compliant hostbridge for the hardware domain. This is because Xen and 
> the hardware domain should not access the configuration space at the 
> same time. 
Yes as discussed on this topic on list few weeks back.
> We may also perform some tasks (i.e MSI mapping, memory mapping) or 
> sanitizing when the configuration space is updated by the hardware 
> domain.
>
> Cheers,
>

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