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Date: Fri, 23 Jan 2026 16:16:33 -0800
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Subject: Re: [PATCH] mshv: Make MSHV mutually exclusive with KEXEC
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To: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>,
 kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
 decui@microsoft.com, longli@microsoft.com
Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org
References: <176920684805.250171.6817228088359793537.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net>
From: Mukesh R <mrathor@linux.microsoft.com>
In-Reply-To: <176920684805.250171.6817228088359793537.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net>
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On 1/23/26 14:20, 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.
> 
> Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.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
> 
> 

Will this affect CRASH kexec? I see few CONFIG_CRASH_DUMP in kexec.c
implying that crash dump might be involved. Or did you test kdump
and it was fine?

Thanks,
-Mukesh