linux-kernel - Re: [PATCH v3] Drivers: hv: ioctl for self targeted passthrough hvcalls

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Message-ID: <b7170d08-8cd2-4add-8abd-8013017203c9@linux.microsoft.com>
Date: Wed, 19 Nov 2025 15:09:28 -0800
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Anirudh Rayabharam <anirudh@...rudhrb.com>,
 "K. Y. Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>, Long Li <longli@...rosoft.com>
Cc: linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] Drivers: hv: ioctl for self targeted passthrough
 hvcalls

On 11/19/2025 9:17 AM, Anirudh Rayabharam wrote:
> From: Anirudh Rayabharam (Microsoft) <anirudh@...rudhrb.com>
> 
> Allow MSHV_ROOT_HVCALL IOCTL on the /dev/mshv fd. This IOCTL would
> execute a passthrough hypercall targeting the root/parent partition
> i.e. HV_PARTITION_ID_SELF.
> 
> This will be useful for the VMM to query things like supported
> synthetic processor features, supported VMM capabiliites etc.
> 
> Since hypercalls targeting the host partition could potentially perform
> privileged operations, allow only a limited set of hypercalls. To begin
> with, allow only:
> 
> 	HVCALL_GET_PARTITION_PROPERTY
> 	HVCALL_GET_PARTITION_PROPERTY_EX
> 
> Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh@...rudhrb.com>
> ---
> 
> v3: restricted the allowed self-targeted passthrough hypercalls to
>     smaller, carefully selected list.
> v2: rebased on latest hyperv-next
> 
> ---
>  drivers/hv/mshv_root_main.c | 47 ++++++++++++++++++++++++++++++-------
>  1 file changed, 38 insertions(+), 9 deletions(-)
> 
Reviewed-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>