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? Thanks, -Christoffer -- 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
