linux-kernel - RE: [PATCH v5 08/10] x86: hyperv: Add mshv_handler irq handler and setup function

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Message-ID:
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Date: Fri, 7 Mar 2025 23:45:10 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
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Subject: RE: [PATCH v5 08/10] x86: hyperv: Add mshv_handler irq handler and
 setup function

From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Friday, March 7, 2025 3:30 PM
> 
> On 3/7/2025 9:44 AM, Michael Kelley wrote:
> > From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Wednesday, February 26, 2025 3:08 PM
> >
> >>
> >> This will handle SYNIC interrupts such as intercepts, doorbells, and
> >> scheduling messages intended for the mshv driver.
> >
> > Could you provide a bit more detailed commit message? How does
> > the mshv_handler() relate to the vmbus_handler()? From the code
> > mshv_handler() goes first, and I'm assuming it processes what it
> > knows about (intercepts, doorbells, scheduling messages?) and
> > then hands off control to the vmbus_handler() to handle the usual
> > VMbus-related message and channel interrupts. But it would be
> > nice to have the commit message or code comments describe the
> > overall intent and any obscure aspects of the relationship.
> >
> > And avoid references to "This" or "This patch". :-)
> >
> 
> You've described it pretty well, I don't know if there's too much
> more to say given this patch doesn't introduce the handler code.
> 
> I can try to improve it, something like:
> "
> mshv_handler() will be used to process messages related to managing
> guest partitions such as intercepts, doorbells, and scheduling messages.
> 
> In a (non-nested) root partition, the same interrupt vector is shared
> between the vmbus and mshv_root drivers.
> 
> Introduce a stub for mshv_handler() and call it in
> sysvec_hyperv_callback alongside vmbus_handler().
> 
> Even though both handlers will be called for every Hyper-V interrupt,
> the messages for each driver are delivered to different offsets within
> the SYNIC message page, so they won't step on each other.
> "
> 
> Does that work?

Yes, that works. I was going to ask how the two handlers could
Both be used on the same interrupt, and you've provided the
explanation, which is perfect. ;-)

Minor tweak: Start the first sentence as an imperative:

   Add mshv_handler() to process messages related .....

Michael