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

[Matthew Rosato <mjrosato@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>