From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Boris Brezillon <boris.brezillon@collabora.com>,
Thomas Zimmermann <tzimmermann@suse.de>,
Michal Hocko <mhocko@suse.com>, Sergio Lopez <slp@redhat.com>,
Christian Koenig <christian.koenig@amd.com>,
Huang Rui <ray.huang@amd.com>,
bcm-kernel-feedback-list@broadcom.com,
dri-devel@lists.freedesktop.org, linux-mm@kvack.org
Subject: Re: [PATCH RFT 0/3] mm, drm: ensure .fault() does not have to be followed by .pfn_mkwrite() for write faults
Date: Tue, 4 Aug 2026 14:19:28 +0200 [thread overview]
Message-ID: <4b9233dd-4f1d-47e0-b583-8e1436d4a074@kernel.org> (raw)
In-Reply-To: <CABgObfaCTroScRykMHRk6fLktzG7CT2Prp2f-CCCANfuagv_MQ@mail.gmail.com>
On 8/4/26 09:50, Paolo Bonzini wrote:
> On Mon, Aug 3, 2026 at 5:18 PM David Hildenbrand (Arm) <david@kernel.org> wrote:
>>>
>> I was wondering about the following:
>>
>> mprotect(PROT_READ)
>>
>> followed by
>>
>> mprotect(PROT_READ | PROT_WRITE)
>>
>> You'd similarly end up without the writable bit in the PTE, and apparently there is not really a way
>> to recover from this.
>
> Why not? mprotect_fixup() calls vma_set_page_prot(), the PTE as you
> say lacks the writable bit (unless pte_dirty(pte)), and then the next
> fault calls .pfn_mkwrite().
Ah, if this works, great. I guess I was confused about your explanation about
fixup_user_fault().
So this really only about avoiding the second fault, makes sense thanks!
--
Cheers,
David
next prev parent reply other threads:[~2026-08-04 12:19 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-31 16:43 [PATCH RFT 0/3] mm, drm: ensure .fault() does not have to be followed by .pfn_mkwrite() for write faults Paolo Bonzini
2026-07-31 16:43 ` [PATCH RFT 1/3] mm: export variants of vmf_insert_pfn* for use with pfn_mkwrite() Paolo Bonzini
2026-08-03 12:16 ` David Hildenbrand (Arm)
2026-08-04 13:52 ` Christoph Hellwig
2026-08-04 14:35 ` Paolo Bonzini
2026-07-31 16:43 ` [PATCH RFT 2/3] drm/shmem_helper: use vmf_insert_pfn_mkwrite() Paolo Bonzini
2026-07-31 17:06 ` sashiko-bot
2026-08-03 9:55 ` Boris Brezillon
2026-07-31 16:43 ` [PATCH RFT 3/3] drm/ttm, drm/vmwgfx: directly create writable PTEs when mkwrite is in use Paolo Bonzini
2026-07-31 17:04 ` sashiko-bot
2026-08-03 7:30 ` [PATCH RFT 0/3] mm, drm: ensure .fault() does not have to be followed by .pfn_mkwrite() for write faults Sergio Lopez Pascual
2026-08-03 11:54 ` David Hildenbrand (Arm)
2026-08-03 14:19 ` Paolo Bonzini
2026-08-03 15:18 ` David Hildenbrand (Arm)
2026-08-04 7:50 ` Paolo Bonzini
2026-08-04 12:19 ` David Hildenbrand (Arm) [this message]
2026-08-03 16:52 ` Paolo Bonzini
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