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 <shank...@codeaurora.org>
---
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.
