On Mon, Aug 29, 2016 at 10:51:14PM -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() > prototype is simplified and caller pushes the regs x0-x1 to stack > instead of regs x0-x3. > > Signed-off-by: Shanker Donthineni <shank...@codeaurora.org>
This looks reasonable to me: Reviewed-by: Christoffer Dall <christoffer.d...@linaro.org> Unless Marc has any insight into this having a negative effect on ARM CPUs, I'll go ahead an merge this. -Christoffer > --- > 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 | 11 +++-- > 2 files changed, 57 insertions(+), 55 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S > index ce9e5e5..f70489a 100644 > --- a/arch/arm64/kvm/hyp/entry.S > +++ b/arch/arm64/kvm/hyp/entry.S > @@ -55,75 +55,76 @@ > */ > 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)] > + // Restore guest regs x19-x29, lr > + restore_callee_saved_regs x18 > > - // x19-x29, lr > - restore_callee_saved_regs x1 > - > - // Last bits of the 64bit state > - ldp x0, x1, [sp], #16 > + // Restore guest reg x18 > + ldr x18, [x18, #CPU_XREG_OFFSET(18)] > > // Do not touch any register after this! > eret > ENDPROC(__guest_enter) > > +/* > + * void __guest_exit(u64 exit_reason, struct kvm_vcpu *vcpu); > + */ > 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) > > diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S > index f6d9694..06e8b3b 100644 > --- a/arch/arm64/kvm/hyp/hyp-entry.S > +++ b/arch/arm64/kvm/hyp/hyp-entry.S > @@ -121,14 +121,15 @@ el1_trap: > cmp x2, #ESR_ELx_EC_FP_ASIMD > b.eq __fpsimd_guest_restore > > - mrs x0, tpidr_el2 > - mov x1, #ARM_EXCEPTION_TRAP > + ldp x2, x3, [sp], #16 > + 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. >
