KVM: Drop FOLL_GET in GUP when doing async page fault

Page pinning is not mandatory in kvm async page fault processing since
after async page fault event is delivered to a guest it accesses page once
again and does its own GUP.  Drop the FOLL_GET flag in GUP in async_pf
code, and do some simplifying in check/clear processing.

Suggested-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Gu zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: chai wen <chaiw.fnst@cn.fujitsu.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

4 files changed, 12 insertions, 21 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c951c71dc80b..edf2a07df3a3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7298,7 +7298,7 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
         int r;
 
         if ((vcpu->arch.mmu.direct_map != work->arch.direct_map) ||
-              is_error_page(work->page))
+              work->wakeup_all)
                 return;
 
         r = kvm_mmu_reload(vcpu);
@@ -7408,7 +7408,7 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
         struct x86_exception fault;
 
         trace_kvm_async_pf_ready(work->arch.token, work->gva);
-        if (is_error_page(work->page))
+        if (work->wakeup_all)
                 work->arch.token = ~0; /* broadcast wakeup */
         else
                 kvm_del_async_pf_gfn(vcpu, work->arch.gfn);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f6dccde755f6..c9d4236ab442 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -189,7 +189,7 @@ struct kvm_async_pf {
         gva_t gva;
         unsigned long addr;
         struct kvm_arch_async_pf arch;
-        struct page *page;
+        bool   wakeup_all;
 };
 
 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu);
diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index 7005d1109ec9..131a0bda7aec 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -296,23 +296,21 @@ DEFINE_EVENT(kvm_async_pf_nopresent_ready, kvm_async_pf_ready,
 
 TRACE_EVENT(
         kvm_async_pf_completed,
-        TP_PROTO(unsigned long address, struct page *page, u64 gva),
-        TP_ARGS(address, page, gva),
+        TP_PROTO(unsigned long address, u64 gva),
+        TP_ARGS(address, gva),
 
         TP_STRUCT__entry(
                 __field(unsigned long, address)
-                __field(pfn_t, pfn)
                 __field(u64, gva)
                 ),
 
         TP_fast_assign(
                 __entry->address = address;
-                __entry->pfn = page ? page_to_pfn(page) : 0;
                 __entry->gva = gva;
                 ),
 
-        TP_printk("gva %#llx address %#lx pfn %#llx",  __entry->gva,
-                  __entry->address, __entry->pfn)
+        TP_printk("gva %#llx address %#lx",  __entry->gva,
+                  __entry->address)
 );
 
 #endif
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index b197950ac4d5..8631d9c14320 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -56,7 +56,6 @@ void kvm_async_pf_vcpu_init(struct kvm_vcpu *vcpu)
 
 static void async_pf_execute(struct work_struct *work)
 {
-        struct page *page = NULL;
         struct kvm_async_pf *apf =
                 container_of(work, struct kvm_async_pf, work);
         struct mm_struct *mm = apf->mm;
@@ -68,13 +67,12 @@ static void async_pf_execute(struct work_struct *work)
 
         use_mm(mm);
         down_read(&mm->mmap_sem);
-        get_user_pages(current, mm, addr, 1, 1, 0, &page, NULL);
+        get_user_pages(current, mm, addr, 1, 1, 0, NULL, NULL);
         up_read(&mm->mmap_sem);
         unuse_mm(mm);
 
         spin_lock(&vcpu->async_pf.lock);
         list_add_tail(&apf->link, &vcpu->async_pf.done);
-        apf->page = page;
         spin_unlock(&vcpu->async_pf.lock);
 
         /*
@@ -82,7 +80,7 @@ static void async_pf_execute(struct work_struct *work)
          * this point
          */
 
-        trace_kvm_async_pf_completed(addr, page, gva);
+        trace_kvm_async_pf_completed(addr, gva);
 
         if (waitqueue_active(&vcpu->wq))
                 wake_up_interruptible(&vcpu->wq);
@@ -112,8 +110,6 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
                         list_entry(vcpu->async_pf.done.next,
                                    typeof(*work), link);
                 list_del(&work->link);
-                if (!is_error_page(work->page))
-                        kvm_release_page_clean(work->page);
                 kmem_cache_free(async_pf_cache, work);
         }
         spin_unlock(&vcpu->async_pf.lock);
@@ -133,14 +129,11 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
                 list_del(&work->link);
                 spin_unlock(&vcpu->async_pf.lock);
 
-                if (work->page)
-                        kvm_arch_async_page_ready(vcpu, work);
+                kvm_arch_async_page_ready(vcpu, work);
                 kvm_arch_async_page_present(vcpu, work);
 
                 list_del(&work->queue);
                 vcpu->async_pf.queued--;
-                if (!is_error_page(work->page))
-                        kvm_release_page_clean(work->page);
                 kmem_cache_free(async_pf_cache, work);
         }
 }
@@ -163,7 +156,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,
         if (!work)
                 return 0;
 
-        work->page = NULL;
+        work->wakeup_all = false;
         work->vcpu = vcpu;
         work->gva = gva;
         work->addr = gfn_to_hva(vcpu->kvm, gfn);
@@ -203,7 +196,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
         if (!work)
                 return -ENOMEM;
 
-        work->page = KVM_ERR_PTR_BAD_PAGE;
+        work->wakeup_all = true;
         INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 
         spin_lock(&vcpu->async_pf.lock);