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 and not being used anywhere, the same information is available in tpidr_el2. Signed-off-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx> --- arch/arm64/kvm/hyp/entry.S | 66 ++++++++++++++++++++++------------------------ 1 file changed, 32 insertions(+), 34 deletions(-) diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index ce9e5e5..d2e09a1 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -55,37 +55,32 @@ */ 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]! + // Preserve 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 x19-x29, lr + restore_callee_saved_regs x18 - // 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 x0-x18 + 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)] + ldr x18, [x18, #CPU_XREG_OFFSET(18)] // Do not touch any register after this! eret @@ -100,6 +95,16 @@ ENTRY(__guest_exit) add x2, x0, #VCPU_CONTEXT + // Store the guest regs x19-x29, lr + save_callee_saved_regs x2 + + // Retrieve the guest regs x0-x3 from the stack + ldp x21, x22, [sp], #16 // x2, x3 + ldp x19, x20, [sp], #16 // x0, x1 + + // Store the guest regs x0-x18 + stp x19, x20, [x2, #CPU_XREG_OFFSET(0)] + stp x21, x22, [x2, #CPU_XREG_OFFSET(2)] stp x4, x5, [x2, #CPU_XREG_OFFSET(4)] stp x6, x7, [x2, #CPU_XREG_OFFSET(6)] stp x8, x9, [x2, #CPU_XREG_OFFSET(8)] @@ -109,20 +114,13 @@ ENTRY(__guest_exit) 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 + // Restore the host_ctxt from the stack + ldr x2, [sp], #16 - stp x4, x5, [x2, #CPU_XREG_OFFSET(0)] - stp x6, x7, [x2, #CPU_XREG_OFFSET(2)] - - save_callee_saved_regs x2 - - // 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 + // Preserving return code (x1) mov x0, x1 ret ENDPROC(__guest_exit) -- 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. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
