Commit 68381b2b authored by Shanker Donthineni's avatar Shanker Donthineni Committed by Christoffer Dall
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arm64: KVM: Optimize __guest_enter/exit() to save a few instructions



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: default avatarShanker Donthineni <shankerd@codeaurora.org>
Reviewed-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
parent 1fe00098
......@@ -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
......
......@@ -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)
......
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