This patch only saves and restores FP/SIMD registers on Guest access. To do
this cptr_el2 FP/SIMD trap is set on Guest entry and later checked on exit.
lmbench, hackbench show significant improvements, for 30-50% exits FP/SIMD
context is not saved/restored
Signed-off-by: Mario Smarduch <m.smard...@samsung.com>
---
arch/arm64/include/asm/kvm_arm.h | 5 ++++-
arch/arm64/kvm/hyp.S | 46 +++++++++++++++++++++++++++++++++++---
2 files changed, 47 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index ac6fafb..7605e09 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -171,10 +171,13 @@
#define HSTR_EL2_TTEE (1 << 16)
#define HSTR_EL2_T(x) (1 << x)
+/* Hyp Coproccessor Trap Register Shifts */
+#define CPTR_EL2_TFP_SHIFT 10
+
/* Hyp Coprocessor Trap Register */
#define CPTR_EL2_TCPAC (1 << 31)
#define CPTR_EL2_TTA (1 << 20)
-#define CPTR_EL2_TFP (1 << 10)
+#define CPTR_EL2_TFP (1 << CPTR_EL2_TFP_SHIFT)
/* Hyp Debug Configuration Register bits */
#define MDCR_EL2_TDRA (1 << 11)
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 5befd01..de0788f 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -673,6 +673,15 @@
tbz \tmp, #KVM_ARM64_DEBUG_DIRTY_SHIFT, \target
.endm
+/*
+ * Check cptr VFP/SIMD accessed bit, if set VFP/SIMD not accessed by guest.
+ */
+.macro skip_fpsimd_state tmp, target
+ mrs \tmp, cptr_el2
+ tbnz \tmp, #CPTR_EL2_TFP_SHIFT, \target
+.endm
+
+
.macro compute_debug_state target
// Compute debug state: If any of KDE, MDE or KVM_ARM64_DEBUG_DIRTY
// is set, we do a full save/restore cycle and disable trapping.
@@ -763,6 +772,7 @@
ldr x2, [x0, #VCPU_HCR_EL2]
msr hcr_el2, x2
mov x2, #CPTR_EL2_TTA
+ orr x2, x2, #CPTR_EL2_TFP
msr cptr_el2, x2
mov x2, #(1 << 15) // Trap CP15 Cr=15
@@ -785,7 +795,6 @@
.macro deactivate_traps
mov x2, #HCR_RW
msr hcr_el2, x2
- msr cptr_el2, xzr
msr hstr_el2, xzr
mrs x2, mdcr_el2
@@ -912,6 +921,28 @@ __restore_fpsimd:
restore_fpsimd
ret
+switch_to_guest_fpsimd:
+ push x4, lr
+
+ mrs x2, cptr_el2
+ bic x2, x2, #CPTR_EL2_TFP
+ msr cptr_el2, x2
+
+ mrs x0, tpidr_el2
+
+ ldr x2, [x0, #VCPU_HOST_CONTEXT]
+ kern_hyp_va x2
+ bl __save_fpsimd
+
+ add x2, x0, #VCPU_CONTEXT
+ bl __restore_fpsimd
+
+ pop x4, lr
+ pop x2, x3
+ pop x0, x1
+
+ eret
+
/*
* u64 __kvm_vcpu_run(struct kvm_vcpu *vcpu);
*
@@ -932,7 +963,6 @@ ENTRY(__kvm_vcpu_run)
kern_hyp_va x2
save_host_regs
- bl __save_fpsimd
bl __save_sysregs
compute_debug_state 1f
@@ -948,7 +978,6 @@ ENTRY(__kvm_vcpu_run)
add x2, x0, #VCPU_CONTEXT
bl __restore_sysregs
- bl __restore_fpsimd
skip_debug_state x3, 1f
bl __restore_debug
@@ -967,7 +996,9 @@ __kvm_vcpu_return:
add x2, x0, #VCPU_CONTEXT
save_guest_regs
+ skip_fpsimd_state x3, 1f
bl __save_fpsimd
+1:
bl __save_sysregs
skip_debug_state x3, 1f
@@ -986,7 +1017,11 @@ __kvm_vcpu_return:
kern_hyp_va x2
bl __restore_sysregs
+ skip_fpsimd_state x3, 1f
bl __restore_fpsimd
+1:
+ /* Clear FPSIMD and Trace trapping */
+ msr cptr_el2, xzr
skip_debug_state x3, 1f
// Clear the dirty flag for the next run, as all the state has
@@ -1201,6 +1236,11 @@ el1_trap:
* x1: ESR
* x2: ESR_EC
*/
+
+ /* Guest accessed VFP/SIMD registers, save host, restore Guest */
+ cmp x2, #ESR_ELx_EC_FP_ASIMD
+ b.eq switch_to_guest_fpsimd
+
cmp x2, #ESR_ELx_EC_DABT_LOW
mov x0, #ESR_ELx_EC_IABT_LOW
ccmp x2, x0, #4, ne
--
1.7.9.5
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