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-rw-r--r--include/linux/kvm_host.h11
-rw-r--r--include/linux/mm.h1
-rw-r--r--mm/gup.c4
-rw-r--r--virt/kvm/async_pf.c4
-rw-r--r--virt/kvm/kvm_main.c49
5 files changed, 63 insertions, 6 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d44a2d64055..45aaeb3360c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -198,6 +198,17 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva,
int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
#endif
+/*
+ * Carry out a gup that requires IO. Allow the mm to relinquish the mmap
+ * semaphore if the filemap/swap has to wait on a page lock. pagep == NULL
+ * controls whether we retry the gup one more time to completion in that case.
+ * Typically this is called after a FAULT_FLAG_RETRY_NOWAIT in the main tdp
+ * handler.
+ */
+int kvm_get_user_page_io(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long addr, bool write_fault,
+ struct page **pagep);
+
enum {
OUTSIDE_GUEST_MODE,
IN_GUEST_MODE,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8981cc882ed..0f4196a0bc2 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1985,6 +1985,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
+#define FOLL_TRIED 0x800 /* a retry, previous pass started an IO */
typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
void *data);
diff --git a/mm/gup.c b/mm/gup.c
index 91d044b1600..af7ea3e0826 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -281,6 +281,10 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
fault_flags |= FAULT_FLAG_ALLOW_RETRY;
if (*flags & FOLL_NOWAIT)
fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT;
+ if (*flags & FOLL_TRIED) {
+ VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY);
+ fault_flags |= FAULT_FLAG_TRIED;
+ }
ret = handle_mm_fault(mm, vma, address, fault_flags);
if (ret & VM_FAULT_ERROR) {
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index d6a3d0993d8..5ff7f7f2689 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -80,9 +80,7 @@ static void async_pf_execute(struct work_struct *work)
might_sleep();
- down_read(&mm->mmap_sem);
- get_user_pages(NULL, mm, addr, 1, 1, 0, NULL, NULL);
- up_read(&mm->mmap_sem);
+ kvm_get_user_page_io(NULL, mm, addr, 1, NULL);
kvm_async_page_present_sync(vcpu, apf);
spin_lock(&vcpu->async_pf.lock);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 499db0977f3..1c6e8476b24 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1122,6 +1122,43 @@ static int get_user_page_nowait(struct task_struct *tsk, struct mm_struct *mm,
return __get_user_pages(tsk, mm, start, 1, flags, page, NULL, NULL);
}
+int kvm_get_user_page_io(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long addr, bool write_fault,
+ struct page **pagep)
+{
+ int npages;
+ int locked = 1;
+ int flags = FOLL_TOUCH | FOLL_HWPOISON |
+ (pagep ? FOLL_GET : 0) |
+ (write_fault ? FOLL_WRITE : 0);
+
+ /*
+ * If retrying the fault, we get here *not* having allowed the filemap
+ * to wait on the page lock. We should now allow waiting on the IO with
+ * the mmap semaphore released.
+ */
+ down_read(&mm->mmap_sem);
+ npages = __get_user_pages(tsk, mm, addr, 1, flags, pagep, NULL,
+ &locked);
+ if (!locked) {
+ VM_BUG_ON(npages != -EBUSY);
+
+ if (!pagep)
+ return 0;
+
+ /*
+ * The previous call has now waited on the IO. Now we can
+ * retry and complete. Pass TRIED to ensure we do not re
+ * schedule async IO (see e.g. filemap_fault).
+ */
+ down_read(&mm->mmap_sem);
+ npages = __get_user_pages(tsk, mm, addr, 1, flags | FOLL_TRIED,
+ pagep, NULL, NULL);
+ }
+ up_read(&mm->mmap_sem);
+ return npages;
+}
+
static inline int check_user_page_hwpoison(unsigned long addr)
{
int rc, flags = FOLL_TOUCH | FOLL_HWPOISON | FOLL_WRITE;
@@ -1184,9 +1221,15 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
npages = get_user_page_nowait(current, current->mm,
addr, write_fault, page);
up_read(&current->mm->mmap_sem);
- } else
- npages = get_user_pages_fast(addr, 1, write_fault,
- page);
+ } else {
+ /*
+ * By now we have tried gup_fast, and possibly async_pf, and we
+ * are certainly not atomic. Time to retry the gup, allowing
+ * mmap semaphore to be relinquished in the case of IO.
+ */
+ npages = kvm_get_user_page_io(current, current->mm, addr,
+ write_fault, page);
+ }
if (npages != 1)
return npages;