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 9298DCD3430 for ; Mon, 4 May 2026 13:55:06 +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=kjtuPBtUs3wRfxAo9hJlxREU/KDYi77wQBFvfglAVmM=; b=4GxCUfFdEwZlqAW32FfOtdoOIb VJ7+Rnfqwd0GEFCKjfFv/02MK4YfFqP+vw/gl+17NBnteABAq4r4MSLpD8ZCKF/U1qJNLgeoTsouF Rv22stUdYR6Wh2Mxb4XHy6sf5Cn2mVhoSXzjwkmb9xYfN8E4CH0iGRp1uGOlul/E/ajiKCefeQ+FP sos4TGJ89XW5riOzBPG5JwVgj1PiSztMBIUxqDRGg53aHLqKh/mJu7vniEAWwTfqyLt45mvjycUZz Ztr0DYkymmJIwqWF98a5xtIQe++0r8zEBcv3B3IGHapMDjdMn6Y1dcxc04u5fqj296ycgIx1kASj8 folTarog==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wJtlF-0000000DMcn-2Q4Y; Mon, 04 May 2026 13:55:01 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wJtlE-0000000DMc6-15x0 for linux-arm-kernel@lists.infradead.org; Mon, 04 May 2026 13:55:00 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 43B8760018; Mon, 4 May 2026 13:54:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9ABE3C2BCB8; Mon, 4 May 2026 13:54:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777902899; bh=t4kUMwZB57/vEZa0pAXLz4i0ebZS73miLhX964u1D/4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yVEddBoV03Mq5M0vTDjIXlW8BHXs7WAvben0N0FW2Kouj4Ik2fMaA+bjkMrLQUdW3 0lBEsI1i44zkXzAsMm7Mda4aLEtEXYy0L7gccgq6NCUSAVTNrbn+/h/tIBawO9MUit 9G1wqld0T9vPiCBNkU2SQQ9PXeIrqwb8RGBqvyIA= 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 Subject: [PATCH 7.0 025/307] arm64/mm: Enable batched TLB flush in unmap_hotplug_range() Date: Mon, 4 May 2026 15:48:30 +0200 Message-ID: <20260504135143.779476141@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260504135142.814938198@linuxfoundation.org> References: <20260504135142.814938198@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 7.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Anshuman Khandual commit 48478b9f791376b4b89018d7afdfd06865498f65 upstream. 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 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 @@ -1462,10 +1462,14 @@ 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); } @@ -1486,15 +1490,14 @@ 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)); @@ -1519,15 +1522,12 @@ 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)); @@ -1557,6 +1557,7 @@ 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; @@ -1578,6 +1579,9 @@ 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,