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

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Message-ID:
 <SN6PR02MB4157822A214FB16274317457D434A@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Fri, 15 Aug 2025 20:46:52 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>, Wei Liu
	<wei.liu@...nel.org>
CC: "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>, "decui@...rosoft.com" <decui@...rosoft.com>
Subject: RE: [PATCH] hyperv: Add missing field to
 hv_output_map_device_interrupt

From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Friday, August 15, 2025 10:11 AM
> 
> On 8/14/2025 2:16 PM, Wei Liu wrote:
> > 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?
> >>
> 
> Ah, it looks like the *input* struct size (0x50) plus the size of
> 1 cpu bank is 0x58. The output struct size should indeed be 0x38.
> 
> I got them mixed up somehow when writing the email.
> >
> > FWIW the array size 5 here is correct.
> >

OK -- thanks.  Just wanted to be sure everything was right.

FWIW,

Reviewed-by: Michael Kelley <mhklinux@...look.com>