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

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Message-ID: <28395b98-3489-342a-970a-5358e4405f22@linux.ibm.com>
Date:   Fri, 6 May 2022 17:35:01 +0200
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...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



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.


Otherwise this looks sane

Reviewed-by: Christian Borntraeger <borntraeger@...ux.ibm.com>