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[104.9.124.193]) by smtp.gmail.com with ESMTPSA id i18sm602099qkk.115.2021.08.18.15.01.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Aug 2021 15:01:57 -0700 (PDT) From: Peilin Ye To: Andrew Morton , x86@kernel.org, Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Joerg Roedel , Muchun Song , Cong Wang , Peilin Ye , Peilin Ye Subject: [PATCH RESEND v2] docs: x86: Remove obsolete information about x86_64 vmalloc() faulting Date: Wed, 18 Aug 2021 15:01:23 -0700 Message-Id: <20210818220123.2623-1-yepeilin.cs@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- Hi all, Resending this with Muchun's Reviewed-by:. Thanks, Peilin Ye Changes in v2: - More information for x86_32 in commit message (Joerg Roedel ) - Use my new email address for work Documentation/x86/x86_64/mm.rst | 4 ---- 1 file changed, 4 deletions(-) diff --git a/Documentation/x86/x86_64/mm.rst b/Documentation/x86/x86_64/mm.rst index ede1875719fb..9798676bb0bf 100644 --- a/Documentation/x86/x86_64/mm.rst +++ b/Documentation/x86/x86_64/mm.rst @@ -140,10 +140,6 @@ The direct mapping covers all memory in the system up to the highest memory address (this means in some cases it can also include PCI memory holes). -vmalloc space is lazily synchronized into the different PML4/PML5 pages of -the processes using the page fault handler, with init_top_pgt as -reference. - We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual memory window (this size is arbitrary, it can be raised later if needed). The mappings are not part of any other kernel PGD and are only available -- 2.20.1