From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A8005CD98E1 for ; Tue, 16 Jun 2026 17:50:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=pC+3y6u05bo4j+kfEVgXTpJcC8QAQdLa7XJcQZ3gASs=; b=4+Gukb8i4MwkblgkQT+p5oZYjv M7zYx4p4YtFel3rfsk+N1nS0hnUyihzd8C5R0up8iaukz9pO6aGMHK0n6w8yo8Xoak/A45dsny0ci A7pRJmJWQYq0FZf+YXEFUZAYPEND9UWnLipyp/OQv0AOYrb90uLKVGaLAdrFdkc/r+unfAcd63j5Z Pg3X8QS62lRyo/S8KbzSJECihTRf6FwADqkDJt9btU9gXXtTr2YOHRHCgc8Z9t9Vc0y0Yq1BSEkqu hOvUs53/GLgcccXKBI22+P4Ug+6v7Kev20xy1m8ADbZ3jWftfd+2InsNyVtAkaiHIAq/PacnhuIks +FpigjhQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wZXvA-0000000GBQ8-2dla; Tue, 16 Jun 2026 17:49:56 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wZXv9-0000000GBQ1-1I4N for linux-arm-kernel@lists.infradead.org; Tue, 16 Jun 2026 17:49:55 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 986D940BC3; Tue, 16 Jun 2026 17:49:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B1431F000E9; Tue, 16 Jun 2026 17:49:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781632194; bh=pC+3y6u05bo4j+kfEVgXTpJcC8QAQdLa7XJcQZ3gASs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kXcTxd5CKxHajSrkqlik9zm4YaMrhKgkcgR7A3o2tnd59aZjPbLqNBTrzHXh8vmsa Xx3NoZvWtfsE4PcAgLCFTz6VxNY/HqvWciC7Dx06ykBtrSU72MY2HmVVeQ7E1K6Hn9 /CiwIUT0RtXKz2L7mn32LjJ/xWLncac8bMIpOusY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, "David Hildenbrand (Arm)" , Ryan Roberts , Anshuman Khandual , Catalin Marinas , Sasha Levin Subject: [PATCH 6.1 337/522] arm64/mm: Enable batched TLB flush in unmap_hotplug_range() Date: Tue, 16 Jun 2026 20:28:04 +0530 Message-ID: <20260616145141.584613180@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145125.307082728@linuxfoundation.org> References: <20260616145125.307082728@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Anshuman Khandual [ Upstream commit 48478b9f791376b4b89018d7afdfd06865498f65 ] During a memory hot remove operation, both linear and vmemmap mappings for the memory range being removed, get unmapped via unmap_hotplug_range() but mapped pages get freed only for vmemmap mapping. This is just a sequential operation where each table entry gets cleared, followed by a leaf specific TLB flush, and then followed by memory free operation when applicable. This approach was simple and uniform both for vmemmap and linear mappings. But linear mapping might contain CONT marked block memory where it becomes necessary to first clear out all entire in the range before a TLB flush. This is as per the architecture requirement. Hence batch all TLB flushes during the table tear down walk and finally do it in unmap_hotplug_range(). Prior to this fix, it was hypothetically possible for a speculative access to a higher address in the contiguous block to fill the TLB with shattered entries for the entire contiguous range after a lower address had already been cleared and invalidated. Due to the table entries being shattered, the subsequent TLB invalidation for the higher address would not then clear the TLB entries for the lower address, meaning stale TLB entries could persist. Besides it also helps in improving the performance via TLBI range operation along with reduced synchronization instructions. The time spent executing unmap_hotplug_range() improved 97% measured over a 2GB memory hot removal in KVM guest. This scheme is not applicable during vmemmap mapping tear down where memory needs to be freed and hence a TLB flush is required after clearing out page table entry. Cc: Will Deacon Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Closes: https://lore.kernel.org/all/aWZYXhrT6D2M-7-N@willie-the-truck/ Fixes: bbd6ec605c0f ("arm64/mm: Enable memory hot remove") Cc: stable@vger.kernel.org Reviewed-by: David Hildenbrand (Arm) Reviewed-by: Ryan Roberts Signed-off-by: Ryan Roberts Signed-off-by: Anshuman Khandual Signed-off-by: Catalin Marinas [ replaced `__pte_clear()` with `pte_clear()` ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/arm64/mm/mmu.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -925,10 +925,14 @@ static void unmap_hotplug_pte_range(pmd_ WARN_ON(!pte_present(pte)); pte_clear(&init_mm, addr, ptep); - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); - if (free_mapped) + if (free_mapped) { + /* CONT blocks are not supported in the vmemmap */ + WARN_ON(pte_cont(pte)); + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); free_hotplug_page_range(pte_page(pte), PAGE_SIZE, altmap); + } + /* unmap_hotplug_range() flushes TLB for !free_mapped */ } while (addr += PAGE_SIZE, addr < end); } @@ -949,15 +953,14 @@ static void unmap_hotplug_pmd_range(pud_ WARN_ON(!pmd_present(pmd)); if (pmd_sect(pmd)) { pmd_clear(pmdp); - - /* - * One TLBI should be sufficient here as the PMD_SIZE - * range is mapped with a single block entry. - */ - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); - if (free_mapped) + if (free_mapped) { + /* CONT blocks are not supported in the vmemmap */ + WARN_ON(pmd_cont(pmd)); + flush_tlb_kernel_range(addr, addr + PMD_SIZE); free_hotplug_page_range(pmd_page(pmd), PMD_SIZE, altmap); + } + /* unmap_hotplug_range() flushes TLB for !free_mapped */ continue; } WARN_ON(!pmd_table(pmd)); @@ -982,15 +985,12 @@ static void unmap_hotplug_pud_range(p4d_ WARN_ON(!pud_present(pud)); if (pud_sect(pud)) { pud_clear(pudp); - - /* - * One TLBI should be sufficient here as the PUD_SIZE - * range is mapped with a single block entry. - */ - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); - if (free_mapped) + if (free_mapped) { + flush_tlb_kernel_range(addr, addr + PUD_SIZE); free_hotplug_page_range(pud_page(pud), PUD_SIZE, altmap); + } + /* unmap_hotplug_range() flushes TLB for !free_mapped */ continue; } WARN_ON(!pud_table(pud)); @@ -1020,6 +1020,7 @@ static void unmap_hotplug_p4d_range(pgd_ static void unmap_hotplug_range(unsigned long addr, unsigned long end, bool free_mapped, struct vmem_altmap *altmap) { + unsigned long start = addr; unsigned long next; pgd_t *pgdp, pgd; @@ -1041,6 +1042,9 @@ static void unmap_hotplug_range(unsigned WARN_ON(!pgd_present(pgd)); unmap_hotplug_p4d_range(pgdp, addr, next, free_mapped, altmap); } while (addr = next, addr < end); + + if (!free_mapped) + flush_tlb_kernel_range(start, end); } static void free_empty_pte_table(pmd_t *pmdp, unsigned long addr,