From 31d8b8d41a7e3e8db081972a63ef1de276ef8ab4 Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Thu, 10 Nov 2016 14:22:02 +0100 Subject: [PATCH] KVM: s390: handle access registers in the run ioctl not in vcpu_put/load Right now we save the host access registers in kvm_arch_vcpu_load and load them in kvm_arch_vcpu_put. Vice versa for the guest access registers. On schedule this means, that we load/save access registers multiple times. e.g. VCPU_RUN with just one reschedule and then return does [from user space via VCPU_RUN] - save the host registers in kvm_arch_vcpu_load (via ioctl) - load the guest registers in kvm_arch_vcpu_load (via ioctl) - do guest stuff - decide to schedule/sleep - save the guest registers in kvm_arch_vcpu_put (via sched) - load the host registers in kvm_arch_vcpu_put (via sched) - save the host registers in switch_to (via sched) - schedule - return - load the host registers in switch_to (via sched) - save the host registers in kvm_arch_vcpu_load (via sched) - load the guest registers in kvm_arch_vcpu_load (via sched) - do guest stuff - decide to go to userspace - save the guest registers in kvm_arch_vcpu_put (via ioctl) - load the host registers in kvm_arch_vcpu_put (via ioctl) [back to user space] As the kernel does not use access registers, we can avoid this reloading and simply piggy back on switch_to (let it save the guest values instead of host values in thread.acrs) by moving the host/guest switch into the VCPU_RUN ioctl function. We now do [from user space via VCPU_RUN] - save the host registers in kvm_arch_vcpu_ioctl_run - load the guest registers in kvm_arch_vcpu_ioctl_run - do guest stuff - decide to schedule/sleep - save the guest registers in switch_to - schedule - return - load the guest registers in switch_to (via sched) - do guest stuff - decide to go to userspace - save the guest registers in kvm_arch_vcpu_ioctl_run - load the host registers in kvm_arch_vcpu_ioctl_run This seems to save about 10% of the vcpu_put/load functions according to perf. As vcpu_load no longer switches the acrs, We can also loading the acrs in kvm_arch_vcpu_ioctl_set_sregs. Suggested-by: Fan Zhang Reviewed-by: Cornelia Huck Signed-off-by: Christian Borntraeger --- arch/s390/kvm/interrupt.c | 2 +- arch/s390/kvm/kvm-s390.c | 12 +++++------- 2 files changed, 6 insertions(+), 8 deletions(-) diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index be4db07..af13f1a 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -415,7 +415,7 @@ static int __write_machine_check(struct kvm_vcpu *vcpu, int rc; mci.val = mchk->mcic; - /* take care of lazy register loading via vcpu load/put */ + /* take care of lazy register loading */ save_fpu_regs(); save_access_regs(vcpu->run->s.regs.acrs); diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 9c7a1ec..4105e1e 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1826,8 +1826,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) /* User space provided an invalid FPC, let's clear it */ current->thread.fpu.fpc = 0; - save_access_regs(vcpu->arch.host_acrs); - restore_access_regs(vcpu->run->s.regs.acrs); gmap_enable(vcpu->arch.enabled_gmap); atomic_or(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags); if (vcpu->arch.cputm_enabled && !is_vcpu_idle(vcpu)) @@ -1851,9 +1849,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) /* Restore host register state */ current->thread.fpu.fpc = vcpu->arch.host_fpregs.fpc; current->thread.fpu.regs = vcpu->arch.host_fpregs.regs; - - save_access_regs(vcpu->run->s.regs.acrs); - restore_access_regs(vcpu->arch.host_acrs); } static void kvm_s390_vcpu_initial_reset(struct kvm_vcpu *vcpu) @@ -2243,7 +2238,6 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, { memcpy(&vcpu->run->s.regs.acrs, &sregs->acrs, sizeof(sregs->acrs)); memcpy(&vcpu->arch.sie_block->gcr, &sregs->crs, sizeof(sregs->crs)); - restore_access_regs(vcpu->run->s.regs.acrs); return 0; } @@ -2740,6 +2734,8 @@ static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) if (riccb->valid) vcpu->arch.sie_block->ecb3 |= 0x01; } + save_access_regs(vcpu->arch.host_acrs); + restore_access_regs(vcpu->run->s.regs.acrs); kvm_run->kvm_dirty_regs = 0; } @@ -2758,6 +2754,8 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) kvm_run->s.regs.pft = vcpu->arch.pfault_token; kvm_run->s.regs.pfs = vcpu->arch.pfault_select; kvm_run->s.regs.pfc = vcpu->arch.pfault_compare; + save_access_regs(vcpu->run->s.regs.acrs); + restore_access_regs(vcpu->arch.host_acrs); } int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) @@ -2874,7 +2872,7 @@ int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu, unsigned long addr) { /* * The guest FPRS and ACRS are in the host FPRS/ACRS due to the lazy - * copying in vcpu load/put. Lets update our copies before we save + * switch in the run ioctl. Let's update our copies before we save * it into the save area */ save_fpu_regs(); -- 2.7.4