From 916d3608df8265a2e3f6214200dbb0b39a5ca383 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Thu, 3 Mar 2022 15:41:14 +0000 Subject: [PATCH] KVM: x86: Use gfn_to_pfn_cache for pv_time Add a new kvm_setup_guest_pvclock() which parallels the existing kvm_setup_pvclock_page(). The latter will be removed once we convert all users to the gfn_to_pfn_cache version. Using the new cache, we can potentially let kvm_set_guest_paused() set the PVCLOCK_GUEST_STOPPED bit directly rather than having to delegate to the vCPU via KVM_REQ_CLOCK_UPDATE. But not yet. Signed-off-by: David Woodhouse Signed-off-by: Paolo Bonzini Message-Id: <20220303154127.202856-5-dwmw2@infradead.org> Signed-off-by: Paolo Bonzini --- arch/x86/include/asm/kvm_host.h | 3 +- arch/x86/kvm/x86.c | 76 ++++++++++++++++++++++++++++++++++------- 2 files changed, 64 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3263147..5a0ff6a 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -751,8 +751,7 @@ struct kvm_vcpu_arch { gpa_t time; struct pvclock_vcpu_time_info hv_clock; unsigned int hw_tsc_khz; - struct gfn_to_hva_cache pv_time; - bool pv_time_enabled; + struct gfn_to_pfn_cache pv_time; /* set guest stopped flag in pvclock flags field */ bool pvclock_set_guest_stopped_request; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7042495..e5d43b4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2249,14 +2249,13 @@ static void kvm_write_system_time(struct kvm_vcpu *vcpu, gpa_t system_time, kvm_make_request(KVM_REQ_GLOBAL_CLOCK_UPDATE, vcpu); /* we verify if the enable bit is set... */ - vcpu->arch.pv_time_enabled = false; - if (!(system_time & 1)) - return; - - if (!kvm_gfn_to_hva_cache_init(vcpu->kvm, - &vcpu->arch.pv_time, system_time & ~1ULL, - sizeof(struct pvclock_vcpu_time_info))) - vcpu->arch.pv_time_enabled = true; + if (system_time & 1) { + kvm_gfn_to_pfn_cache_init(vcpu->kvm, &vcpu->arch.pv_time, vcpu, + KVM_HOST_USES_PFN, system_time & ~1ULL, + sizeof(struct pvclock_vcpu_time_info)); + } else { + kvm_gfn_to_pfn_cache_destroy(vcpu->kvm, &vcpu->arch.pv_time); + } return; } @@ -2961,6 +2960,57 @@ u64 get_kvmclock_ns(struct kvm *kvm) return data.clock; } +static void kvm_setup_guest_pvclock(struct kvm_vcpu *v, + struct gfn_to_pfn_cache *gpc, + unsigned int offset) +{ + struct kvm_vcpu_arch *vcpu = &v->arch; + struct pvclock_vcpu_time_info *guest_hv_clock; + unsigned long flags; + + read_lock_irqsave(&gpc->lock, flags); + while (!kvm_gfn_to_pfn_cache_check(v->kvm, gpc, gpc->gpa, + offset + sizeof(*guest_hv_clock))) { + read_unlock_irqrestore(&gpc->lock, flags); + + if (kvm_gfn_to_pfn_cache_refresh(v->kvm, gpc, gpc->gpa, + offset + sizeof(*guest_hv_clock))) + return; + + read_lock_irqsave(&gpc->lock, flags); + } + + guest_hv_clock = (void *)(gpc->khva + offset); + + /* + * This VCPU is paused, but it's legal for a guest to read another + * VCPU's kvmclock, so we really have to follow the specification where + * it says that version is odd if data is being modified, and even after + * it is consistent. + */ + + guest_hv_clock->version = vcpu->hv_clock.version = (guest_hv_clock->version + 1) | 1; + smp_wmb(); + + /* retain PVCLOCK_GUEST_STOPPED if set in guest copy */ + vcpu->hv_clock.flags |= (guest_hv_clock->flags & PVCLOCK_GUEST_STOPPED); + + if (vcpu->pvclock_set_guest_stopped_request) { + vcpu->hv_clock.flags |= PVCLOCK_GUEST_STOPPED; + vcpu->pvclock_set_guest_stopped_request = false; + } + + memcpy(guest_hv_clock, &vcpu->hv_clock, sizeof(*guest_hv_clock)); + smp_wmb(); + + guest_hv_clock->version = ++vcpu->hv_clock.version; + + mark_page_dirty_in_slot(v->kvm, gpc->memslot, gpc->gpa >> PAGE_SHIFT); + read_unlock_irqrestore(&gpc->lock, flags); + + trace_kvm_pvclock_update(v->vcpu_id, &vcpu->hv_clock); +} + static void kvm_setup_pvclock_page(struct kvm_vcpu *v, struct gfn_to_hva_cache *cache, unsigned int offset) @@ -3106,8 +3156,8 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) vcpu->hv_clock.flags = pvclock_flags; - if (vcpu->pv_time_enabled) - kvm_setup_pvclock_page(v, &vcpu->pv_time, 0); + if (vcpu->pv_time.active) + kvm_setup_guest_pvclock(v, &vcpu->pv_time, 0); if (vcpu->xen.vcpu_info_set) kvm_setup_pvclock_page(v, &vcpu->xen.vcpu_info_cache, offsetof(struct compat_vcpu_info, time)); @@ -3301,7 +3351,7 @@ static int kvm_pv_enable_async_pf_int(struct kvm_vcpu *vcpu, u64 data) static void kvmclock_reset(struct kvm_vcpu *vcpu) { - vcpu->arch.pv_time_enabled = false; + kvm_gfn_to_pfn_cache_destroy(vcpu->kvm, &vcpu->arch.pv_time); vcpu->arch.time = 0; } @@ -5103,7 +5153,7 @@ static int kvm_vcpu_ioctl_x86_set_xcrs(struct kvm_vcpu *vcpu, */ static int kvm_set_guest_paused(struct kvm_vcpu *vcpu) { - if (!vcpu->arch.pv_time_enabled) + if (!vcpu->arch.pv_time.active) return -EINVAL; vcpu->arch.pvclock_set_guest_stopped_request = true; kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu); @@ -6187,7 +6237,7 @@ static int kvm_arch_suspend_notifier(struct kvm *kvm) mutex_lock(&kvm->lock); kvm_for_each_vcpu(i, vcpu, kvm) { - if (!vcpu->arch.pv_time_enabled) + if (!vcpu->arch.pv_time.active) continue; ret = kvm_set_guest_paused(vcpu); -- 2.7.4