On Mon, Feb 01, 2016 at 01:34:16PM +0000, Marc Zyngier wrote: > On 01/02/16 13:16, Christoffer Dall wrote: > > On Mon, Jan 25, 2016 at 03:53:40PM +0000, Marc Zyngier wrote: > >> With VHE, the host never issues an HVC instruction to get into the > >> KVM code, as we can simply branch there. > >> > >> Use runtime code patching to simplify things a bit. > >> > >> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> > >> --- > >> arch/arm64/kvm/hyp.S | 7 +++++++ > >> arch/arm64/kvm/hyp/hyp-entry.S | 38 +++++++++++++++++++++++++++++--------- > >> 2 files changed, 36 insertions(+), 9 deletions(-) > >> > >> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S > >> index 0ccdcbb..0689a74 100644 > >> --- a/arch/arm64/kvm/hyp.S > >> +++ b/arch/arm64/kvm/hyp.S > >> @@ -17,7 +17,9 @@ > >> > >> #include <linux/linkage.h> > >> > >> +#include <asm/alternative.h> > >> #include <asm/assembler.h> > >> +#include <asm/cpufeature.h> > >> > >> /* > >> * u64 kvm_call_hyp(void *hypfn, ...); > >> @@ -38,6 +40,11 @@ > >> * arch/arm64/kernel/hyp_stub.S. > >> */ > >> ENTRY(kvm_call_hyp) > >> +alternative_if_not ARM64_HAS_VIRT_HOST_EXTN > >> hvc #0 > >> ret > >> +alternative_else > >> + b __vhe_hyp_call > >> + nop > >> +alternative_endif > >> ENDPROC(kvm_call_hyp) > >> diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S > >> index 93e8d983..9e0683f 100644 > >> --- a/arch/arm64/kvm/hyp/hyp-entry.S > >> +++ b/arch/arm64/kvm/hyp/hyp-entry.S > >> @@ -38,6 +38,32 @@ > >> ldp x0, x1, [sp], #16 > >> .endm > >> > >> +.macro do_el2_call > >> + /* > >> + * Shuffle the parameters before calling the function > >> + * pointed to in x0. Assumes parameters in x[1,2,3]. > >> + */ > >> + stp lr, xzr, [sp, #-16]! > > > > remind me why this pair isn't just doing "str" instead of "stp" with the > > xzr ? > > Because SP has to be aligned on a 16 bytes boundary at all times. > right, duh. > > > >> + mov lr, x0 > >> + mov x0, x1 > >> + mov x1, x2 > >> + mov x2, x3 > >> + blr lr > >> + ldp lr, xzr, [sp], #16 > >> +.endm > >> + > >> +ENTRY(__vhe_hyp_call) > >> + do_el2_call > >> + /* > >> + * We used to rely on having an exception return to get > >> + * an implicit isb. In the E2H case, we don't have it anymore. > >> + * rather than changing all the leaf functions, just do it here > >> + * before returning to the rest of the kernel. > >> + */ > > > > why is this not the case with an ISB before do_el2_call then? > > That's a good point. I guess the safest thing to do would be to add one, > but looking at the various functions we call, I don't see any that could > go wrong by not having a ISB in their prologue. > > Or maybe you've identified such a case? > I think I argued on Mario's VFP patches that we could rely on an ISB before the hyp call, but they're not merged yet, so, hey... -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
