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

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Message-ID:
 <SN6PR02MB4157B75073B1E6ACDB6405C1D435A@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Thu, 14 Aug 2025 18:57:22 +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>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: "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

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?

Michael

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