On 29/11/16 10:47, Christoffer Dall wrote: > On Tue, Nov 29, 2016 at 09:37:07AM +0000, Marc Zyngier wrote: >> On 28/11/16 19:42, Christoffer Dall wrote: >>> On Mon, Nov 28, 2016 at 06:39:04PM +0000, Marc Zyngier wrote: >>>> On 28/11/16 17:43, Marc Zyngier wrote: >>>>> Hi Jintack, >>>>> >>>>> On 28/11/16 16:46, Jintack Lim wrote: >>>>>> Bit positions of CNTHCTL_EL2 are changing depending on HCR_EL2.E2H bit. >>>>>> EL1PCEN and EL1PCTEN are 1st and 0th bits when E2H is not set, but they >>>>>> are 11th and 10th bits respectively when E2H is set. Current code is >>>>>> unintentionally setting wrong bits to CNTHCTL_EL2 with E2H set, which >>>>>> may allow guest OS to access physical timer. So, fix it. >>>>>> >>>>>> Signed-off-by: Jintack Lim <jintack@xxxxxxxxxxxxxxx> >>>>>> --- >>>>>> arch/arm/include/asm/kvm_timer.h | 33 +++++++++++++++++++ >>>>>> arch/arm64/include/asm/kvm_timer.h | 62 ++++++++++++++++++++++++++++++++++++ >>>>>> include/clocksource/arm_arch_timer.h | 6 ++-- >>>>>> virt/kvm/arm/hyp/timer-sr.c | 8 ++--- >>>>>> 4 files changed, 103 insertions(+), 6 deletions(-) >>>>>> create mode 100644 arch/arm/include/asm/kvm_timer.h >>>>>> create mode 100644 arch/arm64/include/asm/kvm_timer.h >>>>>> >>>> >>>> [...] >>>> >>>>> We could make it nicer (read "faster") by introducing a >>>>> hyp_alternate_select construct that only returns a value instead >>>>> of calling a function. I remember writing something like that >>>>> at some point, and dropping it... >>>> >>>> So here's what this could look like (warning, wacky code ahead, >>>> though I fixed a stupid bug that was present in the previous patch). >>>> The generated code is quite nice (no branch, only an extra mov >>>> instruction on the default path)... Of course, completely untested! >>> >>> Isn't this all about determining which bitmask to use, statically, once, >>> after the system has booted? >>> >>> How about a good old fashioned static variable, or global struct like >>> the global one we use for the VGIC, which sets the proper mit mask >>> during kvm init, and the world-switch code just uses a variable? >> >> We could indeed do that (I've been carried away with my tendency for >> weird and wonderful hacks). >> >> But as Jintack mentioned, there is a much better approach, which is to >> do nothing at all on the VHE path (we can set the permission bits once >> and for all). cntvoff_el2 also falls into the same category of things we >> should be able to only restore and not bother resetting (as it doesn't >> affect the EL2 virtual counter). >> >> Thoughts? >> > Yes, that sounds much better. > > I have some patches to get rid of a lot of things, like cntvoff, during > the world-switch for VHE, so if Jintack just wants to focus on the > cnthctl I will catch cntvoff later. Sound good to me. Thanks, M. -- Jazz is not dead. It just smells funny... -- 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
