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

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Message-ID: <aXabnnCV50Thv9tZ@skinsburskii.localdomain>
Date: Sun, 25 Jan 2026 14:39:26 -0800
From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
To: Mukesh R <mrathor@...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 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.

Thanks,
Stanislav

> Thanks,
> -Mukesh