From mboxrd@z Thu Jan 1 00:00:00 1970 From: christoffer.dall@linaro.org (Christoffer Dall) Date: Thu, 19 Feb 2015 21:57:14 +0100 Subject: [PATCH v2 2/8] arm64: Convert hcalls to use ISS field In-Reply-To: <1422660828.21823.40.camel@infradead.org> References: <6719b2520095926ae0e8ac888663b87f2098f565.1421449714.git.geoff@infradead.org> <1422660828.21823.40.camel@infradead.org> Message-ID: <20150219205714.GC24460@cbox> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 > --- > 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