On Fri, Jan 30, 2015 at 03:33:48PM -0800, Geoff Levand wrote: > To allow for additional hcalls to be defined and to make the arm64 hcall API > more consistent across exception vector routines, change the hcall implementations > to use the ISS field of the ESR_EL2 register to specify the hcall type. how does this make things more consistent? Do we have other examples of things using the immediate field which I'm missing? > > The existing arm64 hcall implementations are limited in that they only allow > for two distinct hcalls; with the x0 register either zero, or not zero. Also, > the API of the hyp-stub exception vector routines and the KVM exception vector > routines differ; hyp-stub uses a non-zero value in x0 to implement > __hyp_set_vectors, whereas KVM uses it to implement kvm_call_hyp. this seems orthogonal to the use of the immediate field vs. x0 though, so why it the immediate field preferred again? > > Define three new preprocessor macros HVC_CALL_HYP, HVC_GET_VECTORS, and > HVC_SET_VECTORS to be used as hcall type specifiers and convert the > existing __hyp_get_vectors(), __hyp_set_vectors() and kvm_call_hyp() routines > to use these new macros when executing an HVC call. Also change the > corresponding hyp-stub and KVM el1_sync exception vector routines to use these > new macros. > > Signed-off-by: Geoff Levand <geoff at infradead.org> > --- > arch/arm64/include/asm/virt.h | 27 +++++++++++++++++++++++++++ > arch/arm64/kernel/hyp-stub.S | 32 +++++++++++++++++++++----------- > arch/arm64/kernel/psci.c | 3 ++- > arch/arm64/kvm/hyp.S | 16 +++++++++------- > 4 files changed, 59 insertions(+), 19 deletions(-) > > diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h > index 7a5df52..eb10368 100644 > --- a/arch/arm64/include/asm/virt.h > +++ b/arch/arm64/include/asm/virt.h > @@ -18,6 +18,33 @@ > #ifndef __ASM__VIRT_H > #define __ASM__VIRT_H > > +/* > + * The arm64 hcall implementation uses the ISS field of the ESR_EL2 register to > + * specify the hcall type. The exception handlers are allowed to use registers > + * x17 and x18 in their implementation. Any routine issuing an hcall must not > + * expect these registers to be preserved. > + */ I thought the existing use of registers were based on the arm procedure call standard so we didn't have to worry about adding more caller-save registers. Don't we now have to start adding code around callers to make sure callers know that x17 and x18 may be clobbered? Thanks, -Christoffer
