Re: [PATCH v6 14/21] KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding

Matthew Rosato
2022-05-06T16:00:58Z

On 5/6/22 11:35 AM, Christian Borntraeger wrote:
>
>
> Am 26.04.22 um 22:08 schrieb Matthew Rosato:
> [...]
>> +static inline void unaccount_mem(unsigned long nr_pages)
>> +{
>> +    struct user_struct *user = get_uid(current_user());
>> +
>> +    if (user)
>> +        atomic_long_sub(nr_pages, &user->locked_vm);
>> +    if (current->mm)
>> +        atomic64_sub(nr_pages, &current->mm->pinned_vm);
>> +}
>> +
>> +static inline int account_mem(unsigned long nr_pages)
>> +{
>> +    struct user_struct *user = get_uid(current_user());
>> +    unsigned long page_limit, cur_pages, new_pages;
>> +
>> +    page_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>> +
>> +    do {
>> +        cur_pages = atomic_long_read(&user->locked_vm);
>> +        new_pages = cur_pages + nr_pages;
>> +        if (new_pages > page_limit)
>> +            return -ENOMEM;
>> +    } while (atomic_long_cmpxchg(&user->locked_vm, cur_pages,
>> +                    new_pages) != cur_pages);
>> +
>> +    atomic64_add(nr_pages, &current->mm->pinned_vm);
>> +
>> +    return 0;
>
> user->locked_vm is not available unconditionally. Shall we add
>
> CONFIG_S390 && CONFIG_KVM here?
>
> include/linux/sched/user.h
> #if defined(CONFIG_PERF_EVENTS) || defined(CONFIG_BPF_SYSCALL) || \
>     defined(CONFIG_NET) || defined(CONFIG_IO_URING)
>         atomic_long_t locked_vm;
> #endif
> Or we could get rid of the user memlock checking for now until this is
> more ubiquitous.

Oh, good catch. Per my conversation with Jason in a thread on patch 16,
we will end up with a CONFIG_VFIO_PCI_ZDEV_KVM (or something like that)
-- this could be used instead of CONFIG_S390 && CONFIG_KVM and would
imply both of those anyway

>
>
> Otherwise this looks sane
>
> Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>