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

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Message-ID: <6e3f4d81-dcb5-9a64-a9f8-2c9b319574ef@linux.ibm.com>
Date:   Fri, 6 May 2022 11:55:35 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        linux-s390@...r.kernel.org
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        schnelle@...ux.ibm.com, farman@...ux.ibm.com, pmorel@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        svens@...ux.ibm.com, frankja@...ux.ibm.com, david@...hat.com,
        imbrenda@...ux.ibm.com, vneethv@...ux.ibm.com,
        oberpar@...ux.ibm.com, freude@...ux.ibm.com, thuth@...hat.com,
        pasic@...ux.ibm.com, pbonzini@...hat.com, corbet@....net,
        jgg@...dia.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v6 14/21] KVM: s390: pci: provide routines for
 enabling/disabling interrupt forwarding

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@...ux.ibm.com>