This is a 0th order approximation of how we could potentially force the guest to avoid uncached mappings, at least from the moment the MMU is on. (Before that, all of memory is implicitly classified as Device-nGnRnE) The idea (patch #2) is to trap writes to MAIR_EL1, and replace uncached mappings with cached ones. This way, there is no need to mangle any guest page tables. The downside is that, to do this correctly, we need to always trap writes to the VM sysreg group, which includes registers that the guest may write to very often. To reduce the associated performance hit, patch #1 introduces a fast path for EL2 to perform trivial sysreg writes on behalf of the guest, without the need for a full world switch to the host and back. The main purpose of these patches is to quantify the performance hit, and verify whether the MAIR_EL1 handling works correctly. Ard Biesheuvel (3): arm64: KVM: handle some sysreg writes in EL2 arm64: KVM: mangle MAIR register to prevent uncached guest mappings arm64: KVM: keep trapping of VM sysreg writes enabled arch/arm/kvm/mmu.c | 2 +- arch/arm64/include/asm/kvm_arm.h | 2 +- arch/arm64/kvm/hyp.S | 101 +++++++++++++++++++++++++++++++++++++++ arch/arm64/kvm/sys_regs.c | 63 ++++++++++++++++++++---- 4 files changed, 156 insertions(+), 12 deletions(-) -- 1.8.3.2 -- 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
