On 07/28/2014 10:43 AM, Benjamin Herrenschmidt wrote:
> On Thu, 2014-07-24 at 18:47 +1000, Alexey Kardashevskiy wrote:
>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
>> ---
>
> You need a description.
>
>> 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(¤t->mm->mmap_sem);
>> + locked = current->mm->locked_vm + npages;
>> + lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>> + if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
>> + pr_warn("RLIMIT_MEMLOCK (%ld) exceeded\n",
>> + rlimit(RLIMIT_MEMLOCK));
>> + ret = -ENOMEM;
>> + } else {
>> + current->mm->locked_vm += npages;
>> + }
>> + up_write(¤t->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;
>
> This is called for VFIO only or is it also called when creating TCE
> tables for emulated devices ? Because in the latter case, you don't
> want to account the pages as locked, do you ?
At the moment TCE-containing pages (for emulated TCE) are allocated with
alloc_page() which is kernel memory and therefore always locked, no?
> Also, you need to explain what +1
>
> Finally, do I correctly deduce that creating 10 TCE tables of 2G
> each will end up accounting 20G as locked even if the guest for
> example only has 4G of RAM ?
The user is required to set the limit to 20G, correct. But this does not
mean all 20G will be pinned. Ugly but better than nothing. As I remember
from you explanations, even if we give up real/virtual mode handlers for
H_PUT_TCE&Co, we cannot rely of existing counters in page struct in order
to understand whether we need to account a page again or not so we are
stuck with this code till we have a "clone DDW window" API.
But this patch is not about guest pages, it is about pages with TCEs, there
was no counting for this at all.
>
>> stt = kzalloc(sizeof(*stt) + npages * sizeof(struct page *),
>> GFP_KERNEL);
>
> Ben.
>
>
--
Alexey
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