[PATCH 15/56] KVM: PPC: booke: standard PPC floating point support

Alexander Graf
2012-03-15T12:10:44Z

From: Scott Wood <scottwood@freescale.com>

e500mc has a normal PPC FPU, rather than SPE which is found
on e500v1/v2.

Based on code from Liu Yu <yu.liu@freescale.com>.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
arch/powerpc/include/asm/system.h | 1 +
arch/powerpc/kvm/booke.c | 44 +++++++++++++++++++++++++++++++++++++
arch/powerpc/kvm/booke.h | 30 +++++++++++++++++++++++++
3 files changed, 75 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/include/asm/system.h b/arch/powerpc/include/asm/system.h
index c377457..73eee86 100644
--- a/arch/powerpc/include/asm/system.h
+++ b/arch/powerpc/include/asm/system.h
@@ -140,6 +140,7 @@ extern void via_cuda_init(void);
extern void read_rtc_time(void);
extern void pmac_find_display(void);
extern void giveup_fpu(struct task_struct *);
+extern void load_up_fpu(void);
extern void disable_kernel_fp(void);
extern void enable_kernel_fp(void);
extern void flush_fp_to_thread(struct task_struct *);
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 75dbaeb..0b77be1 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -457,6 +457,11 @@ void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
{
int ret;
+#ifdef CONFIG_PPC_FPU
+ unsigned int fpscr;
+ int fpexc_mode;
+ u64 fpr[32];
+#endif

if (!vcpu->arch.sane) {
kvm_run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
@@ -479,7 +484,46 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
}

kvm_guest_enter();
+
+#ifdef CONFIG_PPC_FPU
+ /* Save userspace FPU state in stack */
+ enable_kernel_fp();
+ memcpy(fpr, current->thread.fpr, sizeof(current->thread.fpr));
+ fpscr = current->thread.fpscr.val;
+ fpexc_mode = current->thread.fpexc_mode;
+
+ /* Restore guest FPU state to thread */
+ memcpy(current->thread.fpr, vcpu->arch.fpr, sizeof(vcpu->arch.fpr));
+ current->thread.fpscr.val = vcpu->arch.fpscr;
+
+ /*
+ * Since we can't trap on MSR_FP in GS-mode, we consider the guest
+ * as always using the FPU. Kernel usage of FP (via
+ * enable_kernel_fp()) in this thread must not occur while
+ * vcpu->fpu_active is set.
+ */
+ vcpu->fpu_active = 1;
+
+ kvmppc_load_guest_fp(vcpu);
+#endif
+
ret = __kvmppc_vcpu_run(kvm_run, vcpu);
+
+#ifdef CONFIG_PPC_FPU
+ kvmppc_save_guest_fp(vcpu);
+
+ vcpu->fpu_active = 0;
+
+ /* Save guest FPU state from thread */
+ memcpy(vcpu->arch.fpr, current->thread.fpr, sizeof(vcpu->arch.fpr));
+ vcpu->arch.fpscr = current->thread.fpscr.val;
+
+ /* Restore userspace FPU state from stack */
+ memcpy(current->thread.fpr, fpr, sizeof(current->thread.fpr));
+ current->thread.fpscr.val = fpscr;
+ current->thread.fpexc_mode = fpexc_mode;
+#endif
+
kvm_guest_exit();

out:
diff --git a/arch/powerpc/kvm/booke.h b/arch/powerpc/kvm/booke.h
index d53bcf2..3bf5eda 100644
--- a/arch/powerpc/kvm/booke.h
+++ b/arch/powerpc/kvm/booke.h
@@ -96,4 +96,34 @@ enum int_class {

void kvmppc_set_pending_interrupt(struct kvm_vcpu *vcpu, enum int_class type);

+/*
+ * Load up guest vcpu FP state if it's needed.
+ * It also set the MSR_FP in thread so that host know
+ * we're holding FPU, and then host can help to save
+ * guest vcpu FP state if other threads require to use FPU.
+ * This simulates an FP unavailable fault.
+ *
+ * It requires to be called with preemption disabled.
+ */
+static inline void kvmppc_load_guest_fp(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_PPC_FPU
+ if (vcpu->fpu_active && !(current->thread.regs->msr & MSR_FP)) {
+ load_up_fpu();
+ current->thread.regs->msr |= MSR_FP;
+ }
+#endif
+}
+
+/*
+ * Save guest vcpu FP state into thread.
+ * It requires to be called with preemption disabled.
+ */
+static inline void kvmppc_save_guest_fp(struct kvm_vcpu *vcpu)
+{
+#ifdef CONFIG_PPC_FPU
+ if (vcpu->fpu_active && (current->thread.regs->msr & MSR_FP))
+ giveup_fpu(current);
+#endif
+}
#endif /* __KVM_BOOKE_H__ */
--
1.6.0.2