diff options
| -rw-r--r-- | include/linux/kvm_host.h | 11 | ||||
| -rw-r--r-- | include/linux/mm.h | 1 | ||||
| -rw-r--r-- | mm/gup.c | 4 | ||||
| -rw-r--r-- | virt/kvm/async_pf.c | 4 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 49 |
5 files changed, 63 insertions, 6 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d44a2d6..45aaeb3 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 8981cc8..0f4196a 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); @@ -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 d6a3d09..5ff7f7f 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 499db09..1c6e847 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(¤t->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; |
