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Peter Anvin" , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Muchun Song , Cong Wang , Peilin Ye Subject: Re: [PATCH RESEND v2] docs: x86: Remove obsolete information about x86_64 vmalloc() faulting In-Reply-To: References: <20210818220123.2623-1-yepeilin.cs@gmail.com> Date: Fri, 20 Aug 2021 11:14:52 -0600 Message-ID: <87bl5srqb7.fsf@meer.lwn.net> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Joerg Roedel writes: > On Wed, Aug 18, 2021 at 03:01:23PM -0700, Peilin Ye wrote: >> From: Peilin Ye >> >> x86_64 vmalloc() mappings are no longer "synchronized" among page tables >> via faulting since commit 6eb82f994026 ("x86/mm: Pre-allocate P4D/PUD >> pages for vmalloc area"), since the corresponding P4D or PUD pages are >> now preallocated at boot, by preallocate_vmalloc_pages(). Drop the >> "lazily synchronized" description for less confusion. >> >> While this file is x86_64-specific, it is worth noting that things are >> different for x86_32, where vmalloc()-related changes to `init_mm.pgd` are >> synchronized to all page tables in the system during runtime, via >> arch_sync_kernel_mappings(). Unfortunately, this synchronization is >> subject to race condition, which is further handled via faulting, see >> vmalloc_fault(). See commit 4819e15f740e ("x86/mm/32: Bring back vmalloc >> faulting on x86_32") for more details. >> >> Reviewed-by: Muchun Song >> Signed-off-by: Peilin Ye > > Reviewed-by: Joerg Roedel Applied, thanks. jon