On Tue, Aug 30, 2016 at 09:08:32PM -0500, Shanker Donthineni wrote: > We are doing an unnecessary stack push/pop operation when restoring > the guest registers x0-x18 in __guest_enter(). This patch saves the > two instructions by using x18 as a base register. No need to store > the vcpu context pointer in stack because it is redundant, the same > information is available in tpidr_el2. The function __guest_exit() > calling convention is slightly modified, caller only pushes the regs > x0-x1 to stack instead of regs x0-x3. > > Signed-off-by: Shanker Donthineni <shank...@codeaurora.org> > Reviewed-by: Christoffer Dall <christoffer.d...@linaro.org>
Applied, thanks. -Christoffer > --- > Tested this patch using the Qualcomm QDF24XXX platform. > > Changes since v2: > Removed macros save_x0_to_x3/restore_x0_to_x3. > Modified el1_sync() to use regs x0 and x1. > Edited commit text. > > Changes since v1: > Incorporated Cristoffer suggestions. > __guest_exit prototype is changed to 'void __guest_exit(u64 reason, struct > kvm_vcpu *vcpu)'. > > arch/arm64/kvm/hyp/entry.S | 101 > ++++++++++++++++++++--------------------- > arch/arm64/kvm/hyp/hyp-entry.S | 37 ++++++--------- > 2 files changed, 63 insertions(+), 75 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S > index ce9e5e5..3967c231 100644 > --- a/arch/arm64/kvm/hyp/entry.S > +++ b/arch/arm64/kvm/hyp/entry.S > @@ -55,79 +55,78 @@ > */ > ENTRY(__guest_enter) > // x0: vcpu > - // x1: host/guest context > - // x2-x18: clobbered by macros > + // x1: host context > + // x2-x17: clobbered by macros > + // x18: guest context > > // Store the host regs > save_callee_saved_regs x1 > > - // Preserve vcpu & host_ctxt for use at exit time > - stp x0, x1, [sp, #-16]! > + // Store the host_ctxt for use at exit time > + str x1, [sp, #-16]! > > - add x1, x0, #VCPU_CONTEXT > + add x18, x0, #VCPU_CONTEXT > > - // Prepare x0-x1 for later restore by pushing them onto the stack > - ldp x2, x3, [x1, #CPU_XREG_OFFSET(0)] > - stp x2, x3, [sp, #-16]! > + // Restore guest regs x0-x17 > + ldp x0, x1, [x18, #CPU_XREG_OFFSET(0)] > + ldp x2, x3, [x18, #CPU_XREG_OFFSET(2)] > + ldp x4, x5, [x18, #CPU_XREG_OFFSET(4)] > + ldp x6, x7, [x18, #CPU_XREG_OFFSET(6)] > + ldp x8, x9, [x18, #CPU_XREG_OFFSET(8)] > + ldp x10, x11, [x18, #CPU_XREG_OFFSET(10)] > + ldp x12, x13, [x18, #CPU_XREG_OFFSET(12)] > + ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)] > + ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)] > > - // x2-x18 > - ldp x2, x3, [x1, #CPU_XREG_OFFSET(2)] > - ldp x4, x5, [x1, #CPU_XREG_OFFSET(4)] > - ldp x6, x7, [x1, #CPU_XREG_OFFSET(6)] > - ldp x8, x9, [x1, #CPU_XREG_OFFSET(8)] > - ldp x10, x11, [x1, #CPU_XREG_OFFSET(10)] > - ldp x12, x13, [x1, #CPU_XREG_OFFSET(12)] > - ldp x14, x15, [x1, #CPU_XREG_OFFSET(14)] > - ldp x16, x17, [x1, #CPU_XREG_OFFSET(16)] > - ldr x18, [x1, #CPU_XREG_OFFSET(18)] > - > - // x19-x29, lr > - restore_callee_saved_regs x1 > - > - // Last bits of the 64bit state > - ldp x0, x1, [sp], #16 > + // Restore guest regs x19-x29, lr > + restore_callee_saved_regs x18 > + > + // Restore guest reg x18 > + ldr x18, [x18, #CPU_XREG_OFFSET(18)] > > // Do not touch any register after this! > eret > ENDPROC(__guest_enter) > > ENTRY(__guest_exit) > - // x0: vcpu > - // x1: return code > - // x2-x3: free > - // x4-x29,lr: vcpu regs > - // vcpu x0-x3 on the stack > - > - add x2, x0, #VCPU_CONTEXT > - > - stp x4, x5, [x2, #CPU_XREG_OFFSET(4)] > - stp x6, x7, [x2, #CPU_XREG_OFFSET(6)] > - stp x8, x9, [x2, #CPU_XREG_OFFSET(8)] > - stp x10, x11, [x2, #CPU_XREG_OFFSET(10)] > - stp x12, x13, [x2, #CPU_XREG_OFFSET(12)] > - stp x14, x15, [x2, #CPU_XREG_OFFSET(14)] > - stp x16, x17, [x2, #CPU_XREG_OFFSET(16)] > - str x18, [x2, #CPU_XREG_OFFSET(18)] > - > - ldp x6, x7, [sp], #16 // x2, x3 > - ldp x4, x5, [sp], #16 // x0, x1 > - > - stp x4, x5, [x2, #CPU_XREG_OFFSET(0)] > - stp x6, x7, [x2, #CPU_XREG_OFFSET(2)] > + // x0: return code > + // x1: vcpu > + // x2-x29,lr: vcpu regs > + // vcpu x0-x1 on the stack > + > + add x1, x1, #VCPU_CONTEXT > + > + // Store the guest regs x2 and x3 > + stp x2, x3, [x1, #CPU_XREG_OFFSET(2)] > + > + // Retrieve the guest regs x0-x1 from the stack > + ldp x2, x3, [sp], #16 // x0, x1 > + > + // Store the guest regs x0-x1 and x4-x18 > + stp x2, x3, [x1, #CPU_XREG_OFFSET(0)] > + stp x4, x5, [x1, #CPU_XREG_OFFSET(4)] > + stp x6, x7, [x1, #CPU_XREG_OFFSET(6)] > + stp x8, x9, [x1, #CPU_XREG_OFFSET(8)] > + stp x10, x11, [x1, #CPU_XREG_OFFSET(10)] > + stp x12, x13, [x1, #CPU_XREG_OFFSET(12)] > + stp x14, x15, [x1, #CPU_XREG_OFFSET(14)] > + stp x16, x17, [x1, #CPU_XREG_OFFSET(16)] > + str x18, [x1, #CPU_XREG_OFFSET(18)] > + > + // Store the guest regs x19-x29, lr > + save_callee_saved_regs x1 > > - save_callee_saved_regs x2 > + // Restore the host_ctxt from the stack > + ldr x2, [sp], #16 > > - // Restore vcpu & host_ctxt from the stack > - // (preserving return code in x1) > - ldp x0, x2, [sp], #16 > // Now restore the host regs > restore_callee_saved_regs x2 > > - mov x0, x1 > ret > ENDPROC(__guest_exit) > > ENTRY(__fpsimd_guest_restore) > + stp x2, x3, [sp, #-16]! > stp x4, lr, [sp, #-16]! > > alternative_if_not ARM64_HAS_VIRT_HOST_EXTN > diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S > index f6d9694..d6cae542 100644 > --- a/arch/arm64/kvm/hyp/hyp-entry.S > +++ b/arch/arm64/kvm/hyp/hyp-entry.S > @@ -27,16 +27,6 @@ > .text > .pushsection .hyp.text, "ax" > > -.macro save_x0_to_x3 > - stp x0, x1, [sp, #-16]! > - stp x2, x3, [sp, #-16]! > -.endm > - > -.macro restore_x0_to_x3 > - ldp x2, x3, [sp], #16 > - ldp x0, x1, [sp], #16 > -.endm > - > .macro do_el2_call > /* > * Shuffle the parameters before calling the function > @@ -79,23 +69,23 @@ ENTRY(__kvm_hyp_teardown) > ENDPROC(__kvm_hyp_teardown) > > el1_sync: // Guest trapped into EL2 > - save_x0_to_x3 > + stp x0, x1, [sp, #-16]! > > alternative_if_not ARM64_HAS_VIRT_HOST_EXTN > mrs x1, esr_el2 > alternative_else > mrs x1, esr_el1 > alternative_endif > - lsr x2, x1, #ESR_ELx_EC_SHIFT > + lsr x0, x1, #ESR_ELx_EC_SHIFT > > - cmp x2, #ESR_ELx_EC_HVC64 > + cmp x0, #ESR_ELx_EC_HVC64 > b.ne el1_trap > > - mrs x3, vttbr_el2 // If vttbr is valid, the 64bit guest > - cbnz x3, el1_trap // called HVC > + mrs x1, vttbr_el2 // If vttbr is valid, the 64bit guest > + cbnz x1, el1_trap // called HVC > > /* Here, we're pretty sure the host called HVC. */ > - restore_x0_to_x3 > + ldp x0, x1, [sp], #16 > > cmp x0, #HVC_GET_VECTORS > b.ne 1f > @@ -113,22 +103,21 @@ alternative_endif > > el1_trap: > /* > - * x1: ESR > - * x2: ESR_EC > + * x0: ESR_EC > */ > > /* Guest accessed VFP/SIMD registers, save host, restore Guest */ > - cmp x2, #ESR_ELx_EC_FP_ASIMD > + cmp x0, #ESR_ELx_EC_FP_ASIMD > b.eq __fpsimd_guest_restore > > - mrs x0, tpidr_el2 > - mov x1, #ARM_EXCEPTION_TRAP > + mrs x1, tpidr_el2 > + mov x0, #ARM_EXCEPTION_TRAP > b __guest_exit > > el1_irq: > - save_x0_to_x3 > - mrs x0, tpidr_el2 > - mov x1, #ARM_EXCEPTION_IRQ > + stp x0, x1, [sp, #-16]! > + mrs x1, tpidr_el2 > + mov x0, #ARM_EXCEPTION_IRQ > b __guest_exit > > ENTRY(__hyp_do_panic) > -- > Qualcomm Datacenter Technologies, Inc. on behalf of the Qualcomm > Technologies, Inc. > Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux > Foundation Collaborative Project. >
