linux-kernel - Re: [PATCH v2 06/30] s390/airq: allow for airq structure that uses an input vector

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Message-ID: <b0055d0c-a745-4f48-4c4a-373d47651b3f@linux.ibm.com>
Date:   Tue, 18 Jan 2022 13:52:55 -0500
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, alex.williamson@...hat.com,
        cohuck@...hat.com, schnelle@...ux.ibm.com, farman@...ux.ibm.com,
        pmorel@...ux.ibm.com, borntraeger@...ux.ibm.com, hca@...ux.ibm.com,
        gor@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        agordeev@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        vneethv@...ux.ibm.com, oberpar@...ux.ibm.com, freude@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/30] s390/airq: allow for airq structure that uses an
 input vector

On 1/17/22 7:29 AM, Claudio Imbrenda wrote:
> On Fri, 14 Jan 2022 15:31:21 -0500
> Matthew Rosato <mjrosato@...ux.ibm.com> wrote:
> 
>> When doing device passthrough where interrupts are being forwarded
>> from host to guest, we wish to use a pinned section of guest memory
>> as the vector (the same memory used by the guest as the vector).
> 
> maybe expand the description of the patch to explain what exactly is
> being done in this patch. Namely: you add a parameter to a function
> (and some logic in the function to use the new parameter), but the
> function is not being used yet. And pinning is also done somewhere else.
> 
> maybe you can add something like
> 
> 	This patch adds a new parameter for airq_iv_create to pass the
> 	existing vector pinned in guest memory and to use it when
> 	needed instead of allocating a new one.
> 
> Apart from that, the patch looks good.
> 

Thanks, will re-work to:

When doing device passthrough where interrupts are being forwarded from 
host to guest, we wish to use a pinned section of guest memory as the 
vector (the same memory used by the guest as the vector).
To accomplish this, add a new parameter for airq_iv_create which allows 
passing an existing vector to be used instead of allocating a new one. 
The caller is responsible for ensuring the vector is pinned in memory as 
well as for unpinning the memory when the vector is no longer needed.
A subsequent patch will use this new parameter for zPCI interpretation.