This patch tracks armv7 fp/simd hardware state with a vcpu lazy flag.
On vcpu_load saves host fpexc and enables FP access, and later enables fp/simd
trapping if lazy flag is not set. On first fp/simd access trap to handler
to save host and restore guest context, disable trapping and set vcpu lazy
flag. On vcpu_put if flag is set save guest and restore host context and
always restore host fpexc.
Signed-off-by: Mario Smarduch <m.smard...@samsung.com>
---
arch/arm/include/asm/kvm_host.h | 33 ++++++++++++++++++++++
arch/arm/kvm/arm.c | 12 ++++++++
arch/arm/kvm/interrupts.S | 58 +++++++++++++++++++++++----------------
arch/arm/kvm/interrupts_head.S | 26 +++++++++++++-----
arch/arm64/include/asm/kvm_host.h | 6 ++++
5 files changed, 104 insertions(+), 31 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index f1bf551..8fc7a59 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -40,6 +40,38 @@
#define KVM_MAX_VCPUS VGIC_V2_MAX_CPUS
+/*
+ * Reads the host FPEXC register, saves it to vcpu context and enables the
+ * FP/SIMD unit.
+ */
+#ifdef CONFIG_VFPv3
+#define kvm_enable_fpexc(vcpu) { \
+ u32 fpexc = 0; \
+ asm volatile( \
+ "mrc p10, 7, %0, cr8, cr0, 0\n" \
+ "str %0, [%1]\n" \
+ "orr %0, %0, #(1 << 30)\n" \
+ "mcr p10, 7, %0, cr8, cr0, 0\n" \
+ : "+r" (fpexc) \
+ : "r" (&vcpu->arch.host_fpexc) \
+ ); \
+}
+#else
+#define kvm_enable_fpexc(vcpu)
+#endif
+
+/* Restores host FPEXC register */
+#ifdef CONFIG_VFPv3
+#define kvm_restore_host_fpexc(vcpu) { \
+ asm volatile( \
+ "mcr p10, 7, %0, cr8, cr0, 0\n" \
+ : : "r" (vcpu->arch.host_fpexc) \
+ ); \
+}
+#else
+#define kvm_restore_host_fpexc(vcpu)
+#endif
+
u32 *kvm_vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num, u32 mode);
int __attribute_const__ kvm_target_cpu(void);
int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
@@ -227,6 +259,7 @@ 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..cfc348a 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -291,10 +291,22 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
vcpu->arch.host_cpu_context = this_cpu_ptr(kvm_host_cpu_state);
kvm_arm_set_running_vcpu(vcpu);
+
+ /* Save and enable FPEXC before we load guest context */
+ kvm_enable_fpexc(vcpu);
}
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
+ /* If the fp/simd registers are dirty save guest, restore host. */
+ if (vcpu->arch.vfp_dirty) {
+ kvm_restore_host_vfp_state(vcpu);
+ vcpu->arch.vfp_dirty = 0;
+ }
+
+ /* Restore host FPEXC trashed in vcpu_load */
+ kvm_restore_host_fpexc(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..1ddaa89 100644
--- a/arch/arm/kvm/interrupts.S
+++ b/arch/arm/kvm/interrupts.S
@@ -28,6 +28,26 @@
#include "interrupts_head.S"
.text
+/**
+ * void kvm_restore_host_vfp_state(struct vcpu *vcpu) -
+ * This function is called from host to save the guest, and restore host
+ * fp/simd hardware context. It's placed outside of hyp start/end region.
+ */
+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
+
+ pop {r4-r7}
+#endif
+ bx lr
+ENDPROC(kvm_restore_host_vfp_state)
__kvm_hyp_code_start:
.globl __kvm_hyp_code_start
@@ -116,22 +136,22 @@ ENTRY(__kvm_vcpu_run)
read_cp15_state store_to_vcpu = 0
write_cp15_state read_from_vcpu = 1
+ set_hcptr_bits set, r4, (HCPTR_TTA)
@ 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
- VFPFMRX r2, FPEXC @ VMRS
- push {r2}
- orr r2, r2, #FPEXC_EN
- VFPFMXR FPEXC, r2 @ VMSR
+ @ fp/simd register file has already been accessed, so skip trap enable.
+ vfp_skip_if_dirty r7, skip_guest_vfp_trap
+ set_hcptr_bits orr, r4, (HCPTR_TCP(10) | HCPTR_TCP(11))
+skip_guest_vfp_trap:
#endif
+ set_hcptr vmentry, r4
@ Configure Hyp-role
configure_hyp_role vmentry
@ Trap coprocessor CRx accesses
set_hstr vmentry
- set_hcptr vmentry, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
set_hdcr vmentry
@ Write configured ID register into MIDR alias
@@ -170,23 +190,8 @@ __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
-
-#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}
- VFPFMXR FPEXC, r2
-#else
-after_vfp_restore:
-#endif
+ set_hcptr_bits clear, r4, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
+ set_hcptr vmexit, r4
@ Reset Hyp-role
configure_hyp_role vmexit
@@ -483,7 +488,12 @@ switch_to_guest_vfp:
push {r3-r7}
@ NEON/VFP used. Turn on VFP access.
- set_hcptr vmtrap, (HCPTR_TCP(10) | HCPTR_TCP(11))
+ set_hcptr_bits clear, r4, (HCPTR_TCP(10) | HCPTR_TCP(11))
+ set_hcptr vmtrap, r4
+
+ @ 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
diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
index 51a5950..b2b698e 100644
--- a/arch/arm/kvm/interrupts_head.S
+++ b/arch/arm/kvm/interrupts_head.S
@@ -589,16 +589,24 @@ ARM_BE8(rev r6, r6 )
mcr p15, 4, r2, c1, c1, 3
.endm
+/* Prepares HCPTR bit mask to set, clear or 'orr' bits */
+.macro set_hcptr_bits op, reg, mask
+ .if \op == set || \op == clear
+ ldr \reg, =\mask
+ .else
+ orr \reg, \reg, #\mask
+ .endif
+.endm
+
+
/* Configures the HCPTR (Hyp Coprocessor Trap Register) on entry/return
* (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
+ mov r3, \mask
.if \operation == vmentry
orr r3, r2, r3 @ Trap coproc-accesses defined in mask
.else
@@ -611,13 +619,17 @@ 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_skip_if_dirty, 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..83e65dd 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 +251,9 @@ 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_enable_fpexc(struct kvm_vcpu *vcpu) {}
+static inline void kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu) {}
+static inline void kvm_restore_host_fpexc(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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