On Sun, Aug 26, 2012 at 7:41 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> On world switch, we save the pointer to the current vcpu on the top
> of the stack. This tends to complicate the exit path a bit as we then
> need to dig into the stack to restore it (we've already pushed a number
> of registers on top of it at that time), not to mention error prone.
>
> A obvious way to simplify this is to use the HTPIDR register, which is an
> architected method to store per-CPU data in HYP mode, and this is
> exactly what this patch does.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/kvm/interrupts.S | 21 +++++++++++++--------
> 1 files changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> index 7fb0ab9..ac680b80 100644
> --- a/arch/arm/kvm/interrupts.S
> +++ b/arch/arm/kvm/interrupts.S
> @@ -502,11 +502,18 @@ ENDPROC(__kvm_flush_vm_context)
> mcr p15, 4, r2, c1, c1, 0
> .endm
>
> +.macro load_vcpu reg
> + mrc p15, 4, \reg, c13, c0, 2 @ HTPIDR
> +.endm
> +
> @ Arguments:
> @ r0: pointer to vcpu struct
> ENTRY(__kvm_vcpu_run)
> hvc #0 @ switch to hyp-mode
>
> + @ Save the vcpu pointer
> + mcr p15, 4, r0, c13, c0, 2 @ HTPIDR
> +
> @ Now we're in Hyp-mode and lr_usr, spsr_hyp are on the stack
> mrs r2, sp_usr
> push {r2} @ Push r13_usr
> @@ -535,8 +542,6 @@ ENTRY(__kvm_vcpu_run)
> VFPFMXR FPEXC, r2 @ VMSR
> #endif
>
> - push {r0} @ Push the VCPU pointer
> -
> @ Configure Hyp-role
> configure_hyp_role 1, r0
>
> @@ -707,7 +712,7 @@ after_vfp_restore:
> @ the vcpu pointer and stuff off the stack and keep our fingers crossed
> beq 99f
> mov r0, #\exception_code
> - pop {r1} @ Load VCPU pointer
> + load_vcpu r1 @ Load VCPU pointer
> .if \exception_code == ARM_EXCEPTION_DATA_ABORT
> mrc p15, 4, r2, c5, c2, 0 @ HSR
> mrc p15, 4, r3, c6, c0, 0 @ HDFAR
> @@ -831,13 +836,12 @@ host_switch_to_hyp:
> mov pc, lr
>
> guest_trap:
> - ldr r1, [sp, #12] @ Load VCPU pointer
> + load_vcpu r1 @ Load VCPU pointer
> str r0, [r1, #VCPU_HSR]
> add r1, r1, #VCPU_USR_REG(3)
> stmia r1, {r3-r12}
> sub r1, r1, #(VCPU_USR_REG(3) - VCPU_USR_REG(0))
> pop {r3, r4, r5}
> - add sp, sp, #4 @ We loaded the VCPU pointer above
> stmia r1, {r3, r4, r5}
> sub r1, r1, #VCPU_USR_REG(0)
>
> @@ -891,7 +895,7 @@ guest_trap:
> @ inject an undefined exception to the guest.
> #ifdef CONFIG_VFPv3
> switch_to_guest_vfp:
> - ldr r0, [sp, #12] @ Load VCPU pointer
> + load_vcpu r0 @ Load VCPU pointer
> push {r3-r7}
>
> @ NEON/VFP used. Turn on VFP access.
> @@ -912,10 +916,11 @@ switch_to_guest_vfp:
> .align
> hyp_irq:
> push {r0}
> - ldr r0, [sp, #4] @ Load VCPU pointer
> + load_vcpu r0 @ Load VCPU pointer
> add r0, r0, #(VCPU_USR_REG(1))
> stmia r0, {r1-r12}
> - pop {r0, r1} @ r1 == vcpu pointer
> + pop {r0}
> + load_vcpu r1 @ Load VCPU pointer again
> str r0, [r1, #VCPU_USR_REG(0)]
>
> mov r0, #ARM_EXCEPTION_IRQ
> --
> 1.7.8.6
>
Thanks,
applied
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
