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 92A60CD343F for ; Fri, 15 May 2026 16:12:47 +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=O8vHgJ4vvkqtxkyisUTo0eeQhbNxkW1pe2hMHmXDTF0=; b=cZbDPXjNFhyTqfTdF1r/4xmQ9s NTyfK1xFRWTcY23v5igXxNc2cvrRllPrQ5YaTHBvM9xFABH0MoyvWHWHFnWFx24+4RnsDhs7LGM9U S8V3j2d0lESs9q3FdpeUQI6udEH5iuGV/uc2/BjHx5t5GfUfZ6Px8nloZvsWCGjwzx2Z5uW6c2n/F EF1hEk6yY+oHVmlH34qtzqMIV8+3bBgZ+ruUJpyO7IYwl0558VGxdSorKKMpADnAAcbLPrLSJwnw2 s3cwfAyLr3124AvwgxsaKhZ1KUI6DD/1tMFon2pT2MIa64IaFIwNFpa7l4MwoZFEL7Dc0OWps3Ae5 4QQMtY+g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wNv9T-00000008pdF-37te; Fri, 15 May 2026 16:12:39 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wNv9O-00000008pba-2fMk for linux-arm-kernel@lists.infradead.org; Fri, 15 May 2026 16:12:34 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id BC842601DB; Fri, 15 May 2026 16:12:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 215F9C2BCB0; Fri, 15 May 2026 16:12:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778861553; bh=0XQnd2YwS/W/uVBWUWi/9pCJKs6cHEZbJMCWmyBkbT0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MirhqWj1beMH0NqazlR+3vSNFFpsWTdabgvs4m7AzVuUt3V9Szw5HSE4kC+QpO9/y q2L2CF/HT8MlVndQbvA5qdN8xyb8Al187vRIjVpPS3h4P0a16xY7KI0AV8YphbNh5I cE7WoP2SJZEvvNi61St7DvrDJg7aNagRvH9XriVs= 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 6.6 372/474] arm64/mm: Enable batched TLB flush in unmap_hotplug_range() Date: Fri, 15 May 2026 17:48:01 +0200 Message-ID: <20260515154723.076108421@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260515154715.053014143@linuxfoundation.org> References: <20260515154715.053014143@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 6.6-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 @@ -870,10 +870,14 @@ 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); } @@ -894,15 +898,14 @@ 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)); @@ -927,15 +930,12 @@ 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)); @@ -965,6 +965,7 @@ 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; @@ -986,6 +987,9 @@ 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,