On Fri, Dec 04, 2020 at 06:37:07PM +0000, Marc Zyngier wrote: > Will recently pointed out that when running on big-little systems that > are known not to be vulnerable to Metldown, guests are not presented > with the CSV3 property if the physical HW include a core that doesn't > have CSV3, despite being known to be safe (it is on the kpti_safe_list). > > Since this is valuable information that can be cheaply given to the > guest, let's just do that. The scheme is the same as what we do for > CSV2, allowing userspace to change the default setting if this doesn't > advertise a safer setting than what the kernel thinks it is. > > * From v1: > - Fix the clearing of ID_AA64PFR0_EL1.CSV3 on update from userspace > - Actually store the userspace value > > Marc Zyngier (2): > arm64: Make the Meltdown mitigation state available > KVM: arm64: Advertise ID_AA64PFR0_EL1.CSV3=1 if the CPUs are > Meltdown-safe Acked-by: Will Deacon <will@xxxxxxxxxx> Will
