linux-kernel - Re: [PATCH] mshv: Make MSHV mutually exclusive with KEXEC

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Message-ID: <xyzkeqng3767mlpzu7xbmgobjr6ob2wp2brocmjczbbl4dypxh@wkibga46f33c>
Date: Tue, 27 Jan 2026 00:19:24 +0530
From: Anirudh Rayabharam <anirudh@...rudhrb.com>
To: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org, 
	decui@...rosoft.com, longli@...rosoft.com, linux-hyperv@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mshv: Make MSHV mutually exclusive with KEXEC

On Fri, Jan 23, 2026 at 10:20:53PM +0000, Stanislav Kinsburskii wrote:
> The MSHV driver deposits kernel-allocated pages to the hypervisor during
> runtime and never withdraws them. This creates a fundamental incompatibility
> with KEXEC, as these deposited pages remain unavailable to the new kernel
> loaded via KEXEC, leading to potential system crashes upon kernel accessing
> hypervisor deposited pages.
> 
> Make MSHV mutually exclusive with KEXEC until proper page lifecycle
> management is implemented.

Someone might want to stop all guest VMs and do a kexec. Which is valid
and would work without any issue for L1VH.

Also, I don't think it is reasonable at all that someone needs to
disable basic kernel functionality such as kexec in order to use our
driver.

Thanks,
Anirudh.

> 
> Signed-off-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
> ---
>  drivers/hv/Kconfig |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> index 7937ac0cbd0f..cfd4501db0fa 100644
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -74,6 +74,7 @@ config MSHV_ROOT
>  	# e.g. When withdrawing memory, the hypervisor gives back 4k pages in
>  	# no particular order, making it impossible to reassemble larger pages
>  	depends on PAGE_SIZE_4KB
> +	depends on !KEXEC
>  	select EVENTFD
>  	select VIRT_XFER_TO_GUEST_WORK
>  	select HMM_MIRROR
> 
>