linux-kernel - Re: [PATCH] hyperv: Add missing field to hv_output_map_device

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Message-ID: <aJ5SOFR8HNqPxBKN@liuwe-devbox-ubuntu-v2.tail21d00.ts.net>
Date: Thu, 14 Aug 2025 21:16:40 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Michael Kelley <mhklinux@...look.com>
Cc: Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kys@...rosoft.com" <kys@...rosoft.com>,
	"haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
	"wei.liu@...nel.org" <wei.liu@...nel.org>,
	"decui@...rosoft.com" <decui@...rosoft.com>
Subject: Re: [PATCH] hyperv: Add missing field to
 hv_output_map_device_interrupt

On Thu, Aug 14, 2025 at 06:57:22PM +0000, Michael Kelley wrote:
> From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Wednesday, August 13, 2025 11:21 AM
> > 
> > This field is unused, but the correct structure size is needed
> > when computing the amount of space for the output argument to
> > reside, so that it does not cross a page boundary.
> > 
> > Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> > ---
> >  include/hyperv/hvhdk_mini.h | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/include/hyperv/hvhdk_mini.h b/include/hyperv/hvhdk_mini.h
> > index 42e7876455b5..858f6a3925b3 100644
> > --- a/include/hyperv/hvhdk_mini.h
> > +++ b/include/hyperv/hvhdk_mini.h
> > @@ -301,6 +301,7 @@ struct hv_input_map_device_interrupt {
> >  /* HV_OUTPUT_MAP_DEVICE_INTERRUPT */
> >  struct hv_output_map_device_interrupt {
> >  	struct hv_interrupt_entry interrupt_entry;
> > +	u64 ext_status_deprecated[5];
> 
> Your email identifying the problem said that without this
> change, struct hv_output_map_device_interrupt is 0x10
> bytes in size, which matches what I calculate from the definition.
> This change adds 0x28 bytes, making the struct size now 0x38
> bytes. But your other email said Hyper-V expects the size to be
> 0x58 bytes. Is array size "5" correct, or is there some other
> cause of the discrepancy?
> 

FWIW the array size 5 here is correct.

Wei

> Michael
> 
> >  } __packed;
> > 
> >  /* HV_INPUT_UNMAP_DEVICE_INTERRUPT */
> > --
> > 2.34.1
> 
>