In a number of cases, KVM cannot give access direct access to the GICv2 GICV region, either because GICV is not page aligned, or its size is not a multiple of the page size. This is especially visible with 16kB/64kB pages and the original GIC-400 layout where each region is only 4k aligned. Instead of disabling KVM altogether (which is the current behaviour), there is some value in trapping each guest GICV access, performing the access as quickly as possible at EL2, and resuming the guest. This allows us to keep KVM enabled on this HW. Implementation wise, this is done with a static key controlling the workaround being enabled, hence coming at zero cost (well, an extra nop on the exit hot path) for unaffected platforms. On the affected HW, I've measured a 10 to 15% overhead for a self-IPI test, which is pretty bad, but still much better than not having a GIC at all. Tested on Juno. Marc Zyngier (5): arm/arm64: KVM: Don't BUG_ON if IT bits are set in ARM mode arm64: KVM: Allow kvm_skip_instr32 to be shared between kernel and HYP code arm64: KVM: vgic-v2: Add the GICV emulation infrastructure arm64: KVM: vgic-v2: Add GICV access from HYP arm64: KVM: vgic-v2: Enable GICV access from HYP if access from guest is unsafe arch/arm/kvm/emulate.c | 4 +- arch/arm64/include/asm/kvm_emulate.h | 49 +++++++++++++++++++++++++ arch/arm64/include/asm/kvm_hyp.h | 1 + arch/arm64/kvm/emulate.c | 47 +----------------------- arch/arm64/kvm/hyp/switch.c | 32 ++++++++++++++++ include/kvm/arm_vgic.h | 6 +++ virt/kvm/arm/hyp/vgic-v2-sr.c | 46 +++++++++++++++++++++++ virt/kvm/arm/vgic/vgic-v2.c | 71 ++++++++++++++++++++++-------------- 8 files changed, 180 insertions(+), 76 deletions(-) -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html