On Mon, Jan 26, 2026 at 12:20:09PM -0800, Mukesh R wrote: > 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 <[email protected]> > > > > --- > > > > 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?
This is an option. But until it's implemented and merged, a user mshv driver gets into a situation where kexec is broken in a non-obvious way. The system may crash at any time after kexec, depending on whether the new kernel touches the pages deposited to hypervisor or not. This is a bad user experience. Therefor it should be explicitly forbidden as it's essentially not supported yet. Thanks, Stanislav > > > Thanks, > > Stanislav > > > > > Thanks, > > > -Mukesh
