On Tue, Jan 13, 2015 at 8:37 AM, Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote:
> Use the more generic get_user_pages_unlocked which has the additional
> benefit of passing FAULT_FLAG_ALLOW_RETRY at the very first page fault
> (which allows the first page fault in an unmapped area to be always
> able to block indefinitely by being allowed to release the mmap_sem).
>
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reviewed-by: Andres Lagar-Cavilla <andreslc@xxxxxxxxxx>
Thanks for the cleanup.
> ---
> include/linux/kvm_host.h | 11 -----------
> virt/kvm/async_pf.c | 2 +-
> virt/kvm/kvm_main.c | 50 ++++--------------------------------------------
> 3 files changed, 5 insertions(+), 58 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 26f1060..d189ee0 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -200,17 +200,6 @@ 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/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
> index 5ff7f7f..44660ae 100644
> --- a/virt/kvm/async_pf.c
> +++ b/virt/kvm/async_pf.c
> @@ -80,7 +80,7 @@ static void async_pf_execute(struct work_struct *work)
>
> might_sleep();
>
> - kvm_get_user_page_io(NULL, mm, addr, 1, NULL);
> + get_user_pages_unlocked(NULL, mm, addr, 1, 1, 0, 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 1cc6e2e..458b9b1 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1128,43 +1128,6 @@ 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);
> -
> - 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;
> @@ -1227,15 +1190,10 @@ 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 {
> - /*
> - * 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);
> - }
> + } else
> + npages = __get_user_pages_unlocked(current, current->mm, addr, 1,
> + write_fault, 0, page,
> + FOLL_TOUCH|FOLL_HWPOISON);
> if (npages != 1)
> return npages;
>
--
Andres Lagar-Cavilla | Google Kernel Team | andreslc@xxxxxxxxxx
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