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From: Alistair Popple <apopple@nvidia.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	robin.murphy@arm.com, will@kernel.org, nicolinc@nvidia.com,
	linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, jgg@nvidia.com,
	John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH] mmu_notifiers: Notify on pte permission upgrades
Date: Tue, 23 May 2023 09:52:55 +1000	[thread overview]
Message-ID: <871qj7apgp.fsf@nvidia.com> (raw)
In-Reply-To: <ZGuFu0VwRfZszABB@arm.com>


Catalin Marinas <catalin.marinas@arm.com> writes:

> On Mon, May 22, 2023 at 04:37:25PM +1000, Alistair Popple wrote:
>> diff --git a/mm/memory.c b/mm/memory.c
>> index f526b9152bef..0ac78c6a232c 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -2098,6 +2098,7 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
>>  	struct mm_struct *mm = vma->vm_mm;
>>  	pte_t *pte, entry;
>>  	spinlock_t *ptl;
>> +	bool changed = false;
>>  
>>  	pte = get_locked_pte(mm, addr, &ptl);
>>  	if (!pte)
>> @@ -2120,8 +2121,10 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
>>  			}
>>  			entry = pte_mkyoung(*pte);
>>  			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>> -			if (ptep_set_access_flags(vma, addr, pte, entry, 1))
>> +			if (ptep_set_access_flags(vma, addr, pte, entry, 1)) {
>>  				update_mmu_cache(vma, addr, pte);
>> +				changed = true;
>> +			}
>>  		}
>>  		goto out_unlock;
>>  	}
>
> I haven't checked all the corner cases but can we not have a
> ptep_set_access_flags_notify() that handles this (and the huge
> equivalent)? It matches the other API like ptep_clear_flush_notify().

Good suggestion, thanks! I can make the implementations architecture
specific too which helps with filtering on platforms that don't need
it. I had assumed the invalidate_range() callbacks could sleep and
therefore couldn't be called under PTL. However
ptep_clear_flush_notify() already calls invalidate_range() under PTL, so
we already assume drivers don't sleep in the invalidate_range()
callbacks.

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WARNING: multiple messages have this Message-ID (diff)
From: Alistair Popple <apopple@nvidia.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	robin.murphy@arm.com, will@kernel.org, nicolinc@nvidia.com,
	linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, jgg@nvidia.com,
	John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH] mmu_notifiers: Notify on pte permission upgrades
Date: Tue, 23 May 2023 09:52:55 +1000	[thread overview]
Message-ID: <871qj7apgp.fsf@nvidia.com> (raw)
In-Reply-To: <ZGuFu0VwRfZszABB@arm.com>


Catalin Marinas <catalin.marinas@arm.com> writes:

> On Mon, May 22, 2023 at 04:37:25PM +1000, Alistair Popple wrote:
>> diff --git a/mm/memory.c b/mm/memory.c
>> index f526b9152bef..0ac78c6a232c 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -2098,6 +2098,7 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
>>  	struct mm_struct *mm = vma->vm_mm;
>>  	pte_t *pte, entry;
>>  	spinlock_t *ptl;
>> +	bool changed = false;
>>  
>>  	pte = get_locked_pte(mm, addr, &ptl);
>>  	if (!pte)
>> @@ -2120,8 +2121,10 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
>>  			}
>>  			entry = pte_mkyoung(*pte);
>>  			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>> -			if (ptep_set_access_flags(vma, addr, pte, entry, 1))
>> +			if (ptep_set_access_flags(vma, addr, pte, entry, 1)) {
>>  				update_mmu_cache(vma, addr, pte);
>> +				changed = true;
>> +			}
>>  		}
>>  		goto out_unlock;
>>  	}
>
> I haven't checked all the corner cases but can we not have a
> ptep_set_access_flags_notify() that handles this (and the huge
> equivalent)? It matches the other API like ptep_clear_flush_notify().

Good suggestion, thanks! I can make the implementations architecture
specific too which helps with filtering on platforms that don't need
it. I had assumed the invalidate_range() callbacks could sleep and
therefore couldn't be called under PTL. However
ptep_clear_flush_notify() already calls invalidate_range() under PTL, so
we already assume drivers don't sleep in the invalidate_range()
callbacks.

  reply	other threads:[~2023-05-22 23:58 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-22  6:37 [PATCH] mmu_notifiers: Notify on pte permission upgrades Alistair Popple
2023-05-22  6:37 ` Alistair Popple
2023-05-22  7:15 ` Qi Zheng
2023-05-22  7:15   ` Qi Zheng
2023-05-22  7:45   ` Alistair Popple
2023-05-22  7:45     ` Alistair Popple
2023-05-22  8:28     ` Qi Zheng
2023-05-22  8:28       ` Qi Zheng
2023-05-22 15:09 ` Catalin Marinas
2023-05-22 15:09   ` Catalin Marinas
2023-05-22 23:52   ` Alistair Popple [this message]
2023-05-22 23:52     ` Alistair Popple
2023-05-22 18:34 ` Sean Christopherson
2023-05-22 18:34   ` Sean Christopherson
2023-05-22 23:50   ` Alistair Popple
2023-05-22 23:50     ` Alistair Popple
2023-05-23  0:06     ` Sean Christopherson
2023-05-23  0:06       ` Sean Christopherson
2023-05-23  0:43       ` Alistair Popple
2023-05-23  0:43         ` Alistair Popple
2023-05-23  1:13     ` John Hubbard
2023-05-23  1:13       ` John Hubbard
2023-05-23  4:35       ` Alistair Popple
2023-05-23  4:35         ` Alistair Popple
2023-05-23  0:55 ` John Hubbard
2023-05-23  0:55   ` John Hubbard
2023-05-23  1:12   ` Alistair Popple
2023-05-23  1:12     ` Alistair Popple
2023-05-23  6:45 ` Christoph Hellwig
2023-05-23  6:45   ` Christoph Hellwig

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