From a4bff3df51472f555ab8dea05a3d2faf4abbf199 Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Thu, 15 Feb 2024 15:29:00 +0000 Subject: [PATCH] KVM: pfncache: remove KVM_GUEST_USES_PFN usage As noted in [1] the KVM_GUEST_USES_PFN usage flag is never set by any callers of kvm_gpc_init(), and for good reason: the implementation is incomplete/broken. And it's not clear that there will ever be a user of KVM_GUEST_USES_PFN, as coordinating vCPUs with mmu_notifier events is non-trivial. Remove KVM_GUEST_USES_PFN and all related code, e.g. dropping KVM_GUEST_USES_PFN also makes the 'vcpu' argument redundant, to avoid having to reason about broken code as __kvm_gpc_refresh() evolves. Moreover, all existing callers specify KVM_HOST_USES_PFN so the usage check in hva_to_pfn_retry() and hence the 'usage' argument to kvm_gpc_init() are also redundant. [1] https://lore.kernel.org/all/ZQiR8IpqOZrOpzHC@google.com Signed-off-by: Paul Durrant Reviewed-by: David Woodhouse Link: https://lore.kernel.org/r/20240215152916.1158-6-paul@xen.org [sean: explicitly call out that guest usage is incomplete] Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 2 +- arch/x86/kvm/xen.c | 14 ++++------ include/linux/kvm_host.h | 11 +------- include/linux/kvm_types.h | 8 ------ virt/kvm/pfncache.c | 59 ++++++--------------------------------- 5 files changed, 15 insertions(+), 79 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f0f37c769a3a..415723a28dce 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12056,7 +12056,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) vcpu->arch.regs_avail = ~0; vcpu->arch.regs_dirty = ~0; - kvm_gpc_init(&vcpu->arch.pv_time, vcpu->kvm, vcpu, KVM_HOST_USES_PFN); + kvm_gpc_init(&vcpu->arch.pv_time, vcpu->kvm); if (!irqchip_in_kernel(vcpu->kvm) || kvm_vcpu_is_reset_bsp(vcpu)) vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE; diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index 2d001a9c6378..e90464225467 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -2108,14 +2108,10 @@ void kvm_xen_init_vcpu(struct kvm_vcpu *vcpu) timer_setup(&vcpu->arch.xen.poll_timer, cancel_evtchn_poll, 0); - kvm_gpc_init(&vcpu->arch.xen.runstate_cache, vcpu->kvm, NULL, - KVM_HOST_USES_PFN); - kvm_gpc_init(&vcpu->arch.xen.runstate2_cache, vcpu->kvm, NULL, - KVM_HOST_USES_PFN); - kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache, vcpu->kvm, NULL, - KVM_HOST_USES_PFN); - kvm_gpc_init(&vcpu->arch.xen.vcpu_time_info_cache, vcpu->kvm, NULL, - KVM_HOST_USES_PFN); + kvm_gpc_init(&vcpu->arch.xen.runstate_cache, vcpu->kvm); + kvm_gpc_init(&vcpu->arch.xen.runstate2_cache, vcpu->kvm); + kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache, vcpu->kvm); + kvm_gpc_init(&vcpu->arch.xen.vcpu_time_info_cache, vcpu->kvm); } void kvm_xen_destroy_vcpu(struct kvm_vcpu *vcpu) @@ -2158,7 +2154,7 @@ void kvm_xen_init_vm(struct kvm *kvm) { mutex_init(&kvm->arch.xen.xen_lock); idr_init(&kvm->arch.xen.evtchn_ports); - kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm, NULL, KVM_HOST_USES_PFN); + kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm); } void kvm_xen_destroy_vm(struct kvm *kvm) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 604ae285d9a9..3e1c04608c67 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1319,21 +1319,12 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn); * * @gpc: struct gfn_to_pfn_cache object. * @kvm: pointer to kvm instance. - * @vcpu: vCPU to be used for marking pages dirty and to be woken on - * invalidation. - * @usage: indicates if the resulting host physical PFN is used while - * the @vcpu is IN_GUEST_MODE (in which case invalidation of - * the cache from MMU notifiers---but not for KVM memslot - * changes!---will also force @vcpu to exit the guest and - * refresh the cache); and/or if the PFN used directly - * by KVM (and thus needs a kernel virtual mapping). * * This sets up a gfn_to_pfn_cache by initializing locks and assigning the * immutable attributes. Note, the cache must be zero-allocated (or zeroed by * the caller before init). */ -void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm, - struct kvm_vcpu *vcpu, enum pfn_cache_usage usage); +void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm); /** * kvm_gpc_activate - prepare a cached kernel mapping and HPA for a given guest diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h index 9d1f7835d8c1..d93f6522b2c3 100644 --- a/include/linux/kvm_types.h +++ b/include/linux/kvm_types.h @@ -49,12 +49,6 @@ typedef u64 hfn_t; typedef hfn_t kvm_pfn_t; -enum pfn_cache_usage { - KVM_GUEST_USES_PFN = BIT(0), - KVM_HOST_USES_PFN = BIT(1), - KVM_GUEST_AND_HOST_USE_PFN = KVM_GUEST_USES_PFN | KVM_HOST_USES_PFN, -}; - struct gfn_to_hva_cache { u64 generation; gpa_t gpa; @@ -69,13 +63,11 @@ struct gfn_to_pfn_cache { unsigned long uhva; struct kvm_memory_slot *memslot; struct kvm *kvm; - struct kvm_vcpu *vcpu; struct list_head list; rwlock_t lock; struct mutex refresh_lock; void *khva; kvm_pfn_t pfn; - enum pfn_cache_usage usage; bool active; bool valid; }; diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c index f3571f44d9af..6f4b537eb25b 100644 --- a/virt/kvm/pfncache.c +++ b/virt/kvm/pfncache.c @@ -25,9 +25,7 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start, unsigned long end, bool may_block) { - DECLARE_BITMAP(vcpu_bitmap, KVM_MAX_VCPUS); struct gfn_to_pfn_cache *gpc; - bool evict_vcpus = false; spin_lock(&kvm->gpc_lock); list_for_each_entry(gpc, &kvm->gpc_list, list) { @@ -37,43 +35,10 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start, if (gpc->valid && !is_error_noslot_pfn(gpc->pfn) && gpc->uhva >= start && gpc->uhva < end) { gpc->valid = false; - - /* - * If a guest vCPU could be using the physical address, - * it needs to be forced out of guest mode. - */ - if (gpc->usage & KVM_GUEST_USES_PFN) { - if (!evict_vcpus) { - evict_vcpus = true; - bitmap_zero(vcpu_bitmap, KVM_MAX_VCPUS); - } - __set_bit(gpc->vcpu->vcpu_idx, vcpu_bitmap); - } } write_unlock_irq(&gpc->lock); } spin_unlock(&kvm->gpc_lock); - - if (evict_vcpus) { - /* - * KVM needs to ensure the vCPU is fully out of guest context - * before allowing the invalidation to continue. - */ - unsigned int req = KVM_REQ_OUTSIDE_GUEST_MODE; - bool called; - - /* - * If the OOM reaper is active, then all vCPUs should have - * been stopped already, so perform the request without - * KVM_REQUEST_WAIT and be sad if any needed to be IPI'd. - */ - if (!may_block) - req &= ~KVM_REQUEST_WAIT; - - called = kvm_make_vcpus_request_mask(kvm, req, vcpu_bitmap); - - WARN_ON_ONCE(called && !may_block); - } } bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len) @@ -206,16 +171,14 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc) * pfn. Note, kmap() and memremap() can both sleep, so this * too must be done outside of gpc->lock! */ - if (gpc->usage & KVM_HOST_USES_PFN) { - if (new_pfn == gpc->pfn) - new_khva = old_khva; - else - new_khva = gpc_map(new_pfn); + if (new_pfn == gpc->pfn) + new_khva = old_khva; + else + new_khva = gpc_map(new_pfn); - if (!new_khva) { - kvm_release_pfn_clean(new_pfn); - goto out_error; - } + if (!new_khva) { + kvm_release_pfn_clean(new_pfn); + goto out_error; } write_lock_irq(&gpc->lock); @@ -346,18 +309,12 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len) return __kvm_gpc_refresh(gpc, gpc->gpa, len); } -void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm, - struct kvm_vcpu *vcpu, enum pfn_cache_usage usage) +void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) { - WARN_ON_ONCE(!usage || (usage & KVM_GUEST_AND_HOST_USE_PFN) != usage); - WARN_ON_ONCE((usage & KVM_GUEST_USES_PFN) && !vcpu); - rwlock_init(&gpc->lock); mutex_init(&gpc->refresh_lock); gpc->kvm = kvm; - gpc->vcpu = vcpu; - gpc->usage = usage; gpc->pfn = KVM_PFN_ERR_FAULT; gpc->uhva = KVM_HVA_ERR_BAD; }