[PATCH v3 2/3] KVM/arm/arm64: enable enhanced armv7 fp/simd lazy switch
Mario Smarduch
m.smarduch at samsung.com
Fri Oct 30 14:56:32 PDT 2015
This patch tracks vfp/simd hardware state with a vcpu lazy flag. vCPU lazy
flag is set on guest access and traps to vfp/simd hardware switch handler. On
vm-enter if lazy flag is set skip trap enable and save host fpexc. On
vm-exit if flag is set skip hardware context switch and return to host with
guest context. In vcpu_put check if vcpu lazy flag is set, and execute a
hardware context switch to restore host.
Also some arm64 field and empty function are added to compile for arm64.
Signed-off-by: Mario Smarduch <m.smarduch at samsung.com>
---
arch/arm/include/asm/kvm_host.h | 1 +
arch/arm/kvm/arm.c | 6 ++++
arch/arm/kvm/interrupts.S | 60 ++++++++++++++++++++++++++++-----------
arch/arm/kvm/interrupts_head.S | 14 +++++----
arch/arm64/include/asm/kvm_host.h | 4 +++
5 files changed, 63 insertions(+), 22 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index f1bf551..a9e86e0 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -227,6 +227,7 @@ int kvm_perf_teardown(void);
void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
+void kvm_restore_host_vfp_state(struct kvm_vcpu *);
static inline void kvm_arch_hardware_disable(void) {}
static inline void kvm_arch_hardware_unsetup(void) {}
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index dc017ad..11a56fe 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -296,6 +296,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
/*
+ * If fp/simd registers are dirty save guest, restore host before
+ * releasing the cpu.
+ */
+ if (vcpu->arch.vfp_dirty)
+ kvm_restore_host_vfp_state(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
* optimized make_all_cpus_request path.
diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
index 900ef6d..ca25314 100644
--- a/arch/arm/kvm/interrupts.S
+++ b/arch/arm/kvm/interrupts.S
@@ -28,6 +28,32 @@
#include "interrupts_head.S"
.text
+/**
+ * void kvm_restore_host_vfp_state(struct vcpu *vcpu) - Executes lazy
+ * fp/simd switch, saves the guest, restores host. Called from host
+ * mode, placed outside of hyp region start/end.
+ */
+ENTRY(kvm_restore_host_vfp_state)
+#ifdef CONFIG_VFPv3
+ push {r4-r7}
+
+ add r7, vcpu, #VCPU_VFP_GUEST
+ store_vfp_state r7
+
+ add r7, vcpu, #VCPU_VFP_HOST
+ ldr r7, [r7]
+ restore_vfp_state r7
+
+ ldr r3, [vcpu, #VCPU_VFP_HOST_FPEXC]
+ VFPFMXR FPEXC, r3
+
+ mov r3, #0
+ strb r3, [vcpu, #VCPU_VFP_DIRTY]
+
+ pop {r4-r7}
+#endif
+ bx lr
+ENDPROC(kvm_restore_host_vfp_state)
__kvm_hyp_code_start:
.globl __kvm_hyp_code_start
@@ -119,11 +145,16 @@ 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
- @ Set FPEXC_EN so the guest doesn't trap floating point instructions
+ @ fp/simd register file has already been accessed, so skip host fpexc
+ @ save and access trap enable.
+ vfp_inlazy_mode r7, skip_guest_vfp_trap
+
VFPFMRX r2, FPEXC @ VMRS
- push {r2}
+ str r2, [vcpu, #VCPU_VFP_HOST_FPEXC]
orr r2, r2, #FPEXC_EN
VFPFMXR FPEXC, r2 @ VMSR
+ set_hcptr vmentry, (HCPTR_TCP(10) | HCPTR_TCP(11))
+skip_guest_vfp_trap:
#endif
@ Configure Hyp-role
@@ -131,7 +162,7 @@ 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)
set_hdcr vmentry
@ Write configured ID register into MIDR alias
@@ -170,22 +201,15 @@ __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}
+ @ If fp/simd not dirty, restore FPEXC which we clobbered on entry.
+ @ Otherwise return with guest FPEXC, later saved in vcpu_put.
+ vfp_inlazy_mode r2, skip_restore_host_fpexc
+ ldr r2, [vcpu, #VCPU_VFP_HOST_FPEXC]
VFPFMXR FPEXC, r2
-#else
-after_vfp_restore:
+skip_restore_host_fpexc:
#endif
@ Reset Hyp-role
@@ -485,6 +509,10 @@ 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
+ strb r1, [vcpu, #VCPU_VFP_DIRTY]
+
@ 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 51a5950..34e71ee 100644
--- a/arch/arm/kvm/interrupts_head.S
+++ b/arch/arm/kvm/interrupts_head.S
@@ -593,10 +593,8 @@ ARM_BE8(rev r6, r6 )
* (hardware reset value is 0). Keep previous value in r2.
* An ISB is emited on vmexit/vmtrap, but executed on vmexit only if
* VFP wasn't already enabled (always executed on vmtrap).
- * 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
@@ -611,13 +609,17 @@ ARM_BE8(rev r6, r6 )
beq 1f
.endif
isb
- .if \label != none
- b \label
- .endif
1:
.endif
.endm
+/* Checks if VFP/SIMD dirty flag is set, if it is branch to label. */
+.macro vfp_inlazy_mode, reg, label
+ ldr \reg, [vcpu, #VCPU_VFP_DIRTY]
+ 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
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 4562459..26a2347 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -157,6 +157,9 @@ struct kvm_vcpu_arch {
/* Interrupt related fields */
u64 irq_lines; /* IRQ and FIQ levels */
+ /* fp/simd dirty flag true if guest accessed register file */
+ bool vfp_dirty;
+
/* Cache some mmu pages needed inside spinlock regions */
struct kvm_mmu_memory_cache mmu_page_cache;
@@ -248,6 +251,7 @@ static inline void kvm_arch_hardware_unsetup(void) {}
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
+static inline void kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu) {}
void kvm_arm_init_debug(void);
void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
--
1.9.1
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