Re: [PATCH v2 03/18] KVM: PPC: Account TCE pages in locked_vm

[Gavin Shan]

On Wed, Jul 23, 2014 at 01:05:49PM +1000, Alexey Kardashevskiy wrote:
>Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
>---
> arch/powerpc/kvm/book3s_64_vio.c | 35 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 34 insertions(+), 1 deletion(-)
>
>diff --git a/arch/powerpc/kvm/book3s_64_vio.c 
>b/arch/powerpc/kvm/book3s_64_vio.c
>index 516f2ee..48b7ed4 100644
>--- a/arch/powerpc/kvm/book3s_64_vio.c
>+++ b/arch/powerpc/kvm/book3s_64_vio.c
>@@ -45,18 +45,48 @@ static long kvmppc_stt_npages(unsigned long window_size)
>                    * sizeof(u64), PAGE_SIZE) / PAGE_SIZE;
> }
>
>+/*
>+ * Checks ulimit in order not to let the user space to pin all
>+ * available memory for TCE tables.
>+ */
>+static long kvmppc_account_memlimit(long npages)
>+{
>+      unsigned long ret = 0, locked, lock_limit;
>+
>+      if (!current->mm)
>+              return -ESRCH; /* process exited */
>+
>+      down_write(&current->mm->mmap_sem);
>+      locked = current->mm->locked_vm + npages;
>+      lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>+      if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {

I took a look on mm/mlock.c::mlock() where the mlock operation
is allowd while we have one of following conditions (not &&) :-)

        /* check against resource limits */
        if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
                error = do_mlock(start, len, 1);

Thanks,
Gavin

>+              pr_warn("RLIMIT_MEMLOCK (%ld) exceeded\n",
>+                              rlimit(RLIMIT_MEMLOCK));
>+              ret = -ENOMEM;
>+      } else {
>+              current->mm->locked_vm += npages;
>+      }
>+      up_write(&current->mm->mmap_sem);
>+
>+      return ret;
>+}
>+
> static void release_spapr_tce_table(struct kvmppc_spapr_tce_table *stt)
> {
>       struct kvm *kvm = stt->kvm;
>       int i;
>+      long npages = kvmppc_stt_npages(stt->window_size);
>
>       mutex_lock(&kvm->lock);
>       list_del(&stt->list);
>-      for (i = 0; i < kvmppc_stt_npages(stt->window_size); i++)
>+      for (i = 0; i < npages; i++)
>               __free_page(stt->pages[i]);
>+
>       kfree(stt);
>       mutex_unlock(&kvm->lock);
>
>+      kvmppc_account_memlimit(-(npages + 1));
>+
>       kvm_put_kvm(kvm);
> }
>
>@@ -112,6 +142,9 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
>       }
>
>       npages = kvmppc_stt_npages(args->window_size);
>+      ret = kvmppc_account_memlimit(npages + 1);
>+      if (ret)
>+              goto fail;
>
>       stt = kzalloc(sizeof(*stt) + npages * sizeof(struct page *),
>                     GFP_KERNEL);
>-- 
>2.0.0
>

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