linux-kernel - Re: [PATCH] mmu_notifiers: Notify on pte permission upgrades

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Message-ID: <87a5xwajn4.fsf@nvidia.com>
Date:   Mon, 22 May 2023 17:45:59 +1000
From:   Alistair Popple <apopple@...dia.com>
To:     Qi Zheng <qi.zheng@...ux.dev>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        robin.murphy@....com, will@...nel.org, nicolinc@...dia.com,
        linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
        jgg@...dia.com, John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mmu_notifiers: Notify on pte permission upgrades


Qi Zheng <qi.zheng@...ux.dev> writes:

> Hi Alistair,
>
> On 2023/5/22 14:37, Alistair Popple wrote:

[...]

>> +	if (changed) {
>> +		struct mmu_notifier_range range;
>> +
>> +		mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_UPGRADE,
>> +					0, vmf->vma, vmf->vma->vm_mm,
>> +					vmf->address & PAGE_MASK,
>> +					(vmf->address & PAGE_MASK) + PAGE_SIZE);
>> +		mmu_notifier_invalidate_range_start(&range);
>> +		mmu_notifier_invalidate_range_end(&range);
>> +	}
>
> There are four similar patterns, can we introduce a helper function to
> deduplicate them?

For sure. How about something like this?

void mmu_notifier_range_start_end(enum mmu_notifier_event event,
                                  struct vm_area_struct *vma,
                                  struct mm_struct *mm,
                                  unsigned long start,
                                  unsigned long end)

As an aside I didn't just use mmu_notifier_invalidate_range() as that
doesn't allow an event type to be set for interval notifiers which may
want to filter this.

>> +
>>   	return 0;
>>   }
>>