On Sat, Jan 17, 2015 at 12:23:34AM +0000, 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. > > 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. > > Define three new preprocessor macros HVC_GET_VECTORS, HVC_SET_VECTORS and > HVC_CALL_HYP and 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> Using the #imm value for HVC to separate what gets called looks fine to me. However, I'd like to see a review from Marc/Christoffer on this patch. Some comments below: > diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h > index 7a5df52..99c319c 100644 > --- a/arch/arm64/include/asm/virt.h > +++ b/arch/arm64/include/asm/virt.h > @@ -21,6 +21,26 @@ > #define BOOT_CPU_MODE_EL1 (0xe11) > #define BOOT_CPU_MODE_EL2 (0xe12) > > +/* > + * HVC_GET_VECTORS - Return the value of the vbar_el2 register. > + */ > + > +#define HVC_GET_VECTORS 1 > + > +/* > + * HVC_SET_VECTORS - Set the value of the vbar_el2 register. > + * > + * @x0: Physical address of the new vector table. > + */ > + > +#define HVC_SET_VECTORS 2 > + > +/* > + * HVC_CALL_HYP - Execute a hyp routine. > + */ > + > +#define HVC_CALL_HYP 3 I think you can ignore this case (make it the default), just define it as 0 as that's the normal use-case after initialisation and avoid checking it explicitly. > /* > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S > index a272f33..e3db3fd 100644 > --- a/arch/arm64/kernel/hyp-stub.S > +++ b/arch/arm64/kernel/hyp-stub.S > @@ -22,6 +22,7 @@ > #include <linux/irqchip/arm-gic-v3.h> > > #include <asm/assembler.h> > +#include <asm/kvm_arm.h> > #include <asm/ptrace.h> > #include <asm/virt.h> > > @@ -53,14 +54,22 @@ ENDPROC(__hyp_stub_vectors) > .align 11 > > el1_sync: > - mrs x1, esr_el2 > - lsr x1, x1, #26 > - cmp x1, #0x16 > - b.ne 2f // Not an HVC trap > - cbz x0, 1f > - msr vbar_el2, x0 // Set vbar_el2 > + mrs x18, esr_el2 > + lsr x17, x18, #ESR_ELx_EC_SHIFT > + and x18, x18, #ESR_ELx_ISS_MASK > + > + cmp x17, #ESR_ELx_EC_HVC64 > + b.ne 2f // Not an HVC trap > + > + cmp x18, #HVC_GET_VECTORS > + b.ne 1f > + mrs x0, vbar_el2 > b 2f > -1: mrs x0, vbar_el2 // Return vbar_el2 > + > +1: cmp x18, #HVC_SET_VECTORS > + b.ne 2f > + msr vbar_el2, x0 > + > 2: eret > ENDPROC(el1_sync) You seem to be using x17 and x18 here freely. Do you have any guarantees that the caller saved/restored those registers? I guess you assume they are temporary registers and the caller first branches to a function (like __kvm_hyp_call) and expects them to be corrupted. But I'm not sure that's always the case. Take for example the __invoke_psci_fn_hvc where the function is in C (we should change this for other reasons). > diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S > index c0d8202..1916c89 100644 > --- a/arch/arm64/kvm/hyp.S > +++ b/arch/arm64/kvm/hyp.S > @@ -27,6 +27,7 @@ > #include <asm/kvm_asm.h> > #include <asm/kvm_mmu.h> > #include <asm/memory.h> > +#include <asm/virt.h> > > #define CPU_GP_REG_OFFSET(x) (CPU_GP_REGS + x) > #define CPU_XREG_OFFSET(x) CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x) > @@ -1106,12 +1107,9 @@ __hyp_panic_str: > * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c). Return values are > * passed in r0 and r1. > * > - * A function pointer with a value of 0 has a special meaning, and is > - * used to implement __hyp_get_vectors in the same way as in > - * arch/arm64/kernel/hyp_stub.S. > */ > ENTRY(kvm_call_hyp) > - hvc #0 > + hvc #HVC_CALL_HYP > ret > ENDPROC(kvm_call_hyp) > > @@ -1142,6 +1140,7 @@ el1_sync: // Guest trapped into EL2 > > mrs x1, esr_el2 > lsr x2, x1, #ESR_ELx_EC_SHIFT > + and x0, x1, #ESR_ELx_ISS_MASK > > cmp x2, #ESR_ELx_EC_HVC64 > b.ne el1_trap > @@ -1150,15 +1149,19 @@ el1_sync: // Guest trapped into EL2 > cbnz x3, el1_trap // called HVC > > /* Here, we're pretty sure the host called HVC. */ > + mov x18, x0 Same comment here about corrupting x18. If it is safe, maybe add some comments in the calling place. > pop x2, x3 > pop x0, x1 > > - /* Check for __hyp_get_vectors */ > - cbnz x0, 1f > + cmp x18, #HVC_GET_VECTORS > + b.ne 1f > mrs x0, vbar_el2 > b 2f > > -1: push lr, xzr > +1: cmp x18, #HVC_CALL_HYP > + b.ne 2f > + > + push lr, xzr At this point, we expect either HVC_GET_VECTORS or HVC_CALL_HYP. I think you can simply assume HVC_CALL_HYP as default and ignore the additional cmp. -- Catalin
