Hi Suzuki, On Tue, 31 Jan 2023 13:47:31 +0000, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote: > > Hi Marc > > On 31/01/2023 09:23, Marc Zyngier wrote: > > From: Jintack Lim <jintack.lim@xxxxxxxxxx> > > > > Add a new ARM64_HAS_NESTED_VIRT feature to indicate that the > > CPU has the ARMv8.3 nested virtualization capability, together > > with the 'kvm-arm.mode=nested' command line option. > > > > This will be used to support nested virtualization in KVM. > > > > Reviewed-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx> > > Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx> > > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx> > > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx> > > [maz: moved the command-line option to kvm-arm.mode] > > Should this be separate kvm-arm mode ? Or can this be tied to > is_kernel_in_hyp_mode() ? Given this mode (from my limited > review) doesn't conflict with normal VHE mode (and RME support), > adding this explicit mode could confuse the user. What is exactly the objection here? NV is more or less a VHE++ mode, but is also completely experimental and incomplete. > In case we need a command line to turn the NV mode on/off, > we could always use the id-override and simply leave this out ? I really want an explicit user buy-in. There is absolutely no way this can be enabled by default, the risks are way too high. Just look at the x86 story: it took them 10 years to enable NV by default. I don't expect to do any better. Thanks, M. -- Without deviation from the norm, progress is not possible.
