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

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Message-ID: <890506f6-9b91-5d59-8c98-086cf5d206bb@linux.microsoft.com>
Date: Mon, 26 Jan 2026 12:20:09 -0800
From: Mukesh R <mrathor@...ux.microsoft.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 1/25/26 14:39, Stanislav Kinsburskii wrote:
> On Fri, Jan 23, 2026 at 04:16:33PM -0800, Mukesh R wrote:
>> 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@...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
>>>
>>>
>>
>> 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?
>>
> 
> Yes, it will. Crash kexec depends on normal kexec functionality, so it
> will be affected as well.

So not sure I understand the reason for this patch. We can just block
kexec if there are any VMs running, right? Doing this would mean any
further developement would be without a ver important and major feature,
right?

> Thanks,
> Stanislav
> 
>> Thanks,
>> -Mukesh