This patch enhances current lazy vfp/simd hardware switch. In addition to
current lazy switch, it tracks vfp/simd hardware state with a vcpu
lazy flag.
vcpu lazy flag is set on guest access and trap to vfp/simd hardware switch
handler. On vm-enter if lazy flag is set skip trap enable and saving
host fpexc. On vm-exit if flag is set skip hardware context switch
and return to host with guest context.
On vcpu_put check if vcpu lazy flag is set, and execute a hardware context
switch to restore host.
Signed-off-by: Mario Smarduch <m.smarduch@xxxxxxxxxxx>
---
arch/arm/include/asm/kvm_asm.h | 1 +
arch/arm/kvm/arm.c | 17 ++++++++++++
arch/arm/kvm/interrupts.S | 60 +++++++++++++++++++++++++++++++-----------
arch/arm/kvm/interrupts_head.S | 12 ++++++---
4 files changed, 71 insertions(+), 19 deletions(-)
diff --git a/arch/arm/include/asm/kvm_asm.h b/arch/arm/include/asm/kvm_asm.h
index 194c91b..4b45d79 100644
--- a/arch/arm/include/asm/kvm_asm.h
+++ b/arch/arm/include/asm/kvm_asm.h
@@ -97,6 +97,7 @@ extern char __kvm_hyp_code_end[];
extern void __kvm_flush_vm_context(void);
extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);
extern void __kvm_tlb_flush_vmid(struct kvm *kvm);
+extern void __kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu);
extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
#endif
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index ce404a5..79f49c7 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -105,6 +105,20 @@ void kvm_arch_check_processor_compat(void *rtn)
*(int *)rtn = 0;
}
+/**
+ * kvm_switch_fp_regs() - switch guest/host VFP/SIMD registers
+ * @vcpu: pointer to vcpu structure.
+ *
+ */
+static void kvm_switch_fp_regs(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_ARM
+ if (vcpu->arch.vfp_lazy == 1) {
+ kvm_call_hyp(__kvm_restore_host_vfp_state, vcpu);
+ vcpu->arch.vfp_lazy = 0;
+ }
+#endif
+}
/**
* kvm_arch_init_vm - initializes a VM data structure
@@ -295,6 +309,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
+ /* Check if Guest accessed VFP registers */
+ kvm_switch_fp_regs(vcpu);
+
/*
* The arch-generic KVM code expects the cpu field of a vcpu to be -1
* if the vcpu is no longer assigned to a cpu. This is used for the
diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
index 900ef6d..6d98232 100644
--- a/arch/arm/kvm/interrupts.S
+++ b/arch/arm/kvm/interrupts.S
@@ -96,6 +96,29 @@ ENTRY(__kvm_flush_vm_context)
bx lr
ENDPROC(__kvm_flush_vm_context)
+/**
+ * void __kvm_restore_host_vfp_state(struct vcpu *vcpu) - Executes a lazy
+ * fp/simd switch, saves the guest, restores host.
+ *
+ */
+ENTRY(__kvm_restore_host_vfp_state)
+#ifdef CONFIG_VFPv3
+ push {r3-r7}
+
+ add r7, r0, #VCPU_VFP_GUEST
+ store_vfp_state r7
+
+ add r7, r0, #VCPU_VFP_HOST
+ ldr r7, [r7]
+ restore_vfp_state r7
+
+ ldr r3, [vcpu, #VCPU_VFP_FPEXC]
+ VFPFMXR FPEXC, r3
+
+ pop {r3-r7}
+#endif
+ bx lr
+ENDPROC(__kvm_restore_host_vfp_state)
/********************************************************************
* Hypervisor world-switch code
@@ -119,11 +142,15 @@ ENTRY(__kvm_vcpu_run)
@ If the host kernel has not been configured with VFPv3 support,
@ then it is safer if we deny guests from using it as well.
#ifdef CONFIG_VFPv3
+ @ r7 must be preserved until next vfp lazy check
+ vfp_inlazy_mode r7, skip_save_host_fpexc
+
@ Set FPEXC_EN so the guest doesn't trap floating point instructions
VFPFMRX r2, FPEXC @ VMRS
- push {r2}
+ str r2, [vcpu, #VCPU_VFP_FPEXC]
orr r2, r2, #FPEXC_EN
VFPFMXR FPEXC, r2 @ VMSR
+skip_save_host_fpexc:
#endif
@ Configure Hyp-role
@@ -131,7 +158,14 @@ ENTRY(__kvm_vcpu_run)
@ Trap coprocessor CRx accesses
set_hstr vmentry
- set_hcptr vmentry, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
+ set_hcptr vmentry, (HCPTR_TTA)
+
+ @ check if vfp_lazy flag set
+ cmp r7, #1
+ beq skip_guest_vfp_trap
+ set_hcptr vmentry, (HCPTR_TCP(10) | HCPTR_TCP(11))
+skip_guest_vfp_trap:
+
set_hdcr vmentry
@ Write configured ID register into MIDR alias
@@ -170,22 +204,14 @@ __kvm_vcpu_return:
@ Don't trap coprocessor accesses for host kernel
set_hstr vmexit
set_hdcr vmexit
- set_hcptr vmexit, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11)), after_vfp_restore
+ set_hcptr vmexit, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
#ifdef CONFIG_VFPv3
- @ Switch VFP/NEON hardware state to the host's
- add r7, vcpu, #VCPU_VFP_GUEST
- store_vfp_state r7
- add r7, vcpu, #VCPU_VFP_HOST
- ldr r7, [r7]
- restore_vfp_state r7
-
-after_vfp_restore:
- @ Restore FPEXC_EN which we clobbered on entry
- pop {r2}
+ vfp_inlazy_mode r2, skip_restore_host_fpexc
+ @ If vfp_lazy is not set, restore FPEXC_EN which we clobbered on entry
+ ldr r2, [vcpu, #VCPU_VFP_FPEXC]
VFPFMXR FPEXC, r2
-#else
-after_vfp_restore:
+skip_restore_host_fpexc:
#endif
@ Reset Hyp-role
@@ -485,6 +511,10 @@ switch_to_guest_vfp:
@ NEON/VFP used. Turn on VFP access.
set_hcptr vmtrap, (HCPTR_TCP(10) | HCPTR_TCP(11))
+ @ set lazy mode flag, switch hardware context on vcpu_put
+ mov r1, #1
+ str r1, [vcpu, #VCPU_VFP_LAZY]
+
@ Switch VFP/NEON hardware state to the guest's
add r7, r0, #VCPU_VFP_HOST
ldr r7, [r7]
diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
index 702740d..4561171 100644
--- a/arch/arm/kvm/interrupts_head.S
+++ b/arch/arm/kvm/interrupts_head.S
@@ -594,7 +594,7 @@ ARM_BE8(rev r6, r6 )
* If a label is specified with vmexit, it is branched to if VFP wasn't
* enabled.
*/
-.macro set_hcptr operation, mask, label = none
+.macro set_hcptr operation, mask
mrc p15, 4, r2, c1, c1, 2
ldr r3, =\mask
.if \operation == vmentry
@@ -609,13 +609,17 @@ ARM_BE8(rev r6, r6 )
beq 1f
.endif
isb
- .if \label != none
- b \label
- .endif
1:
.endif
.endm
+/* Checks if VFP/SIMD lazy flag is set, if it is branch to label. */
+.macro vfp_inlazy_mode, reg, label
+ ldr \reg, [vcpu, #VCPU_VFP_LAZY]
+ cmp \reg, #1
+ beq \label
+.endm
+
/* Configures the HDCR (Hyp Debug Configuration Register) on entry/return
* (hardware reset value is 0) */
.macro set_hdcr operation
--
1.9.1
--
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