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 9EA65FF885A for ; Tue, 28 Apr 2026 18:53:23 +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=KDGPqequApuA+vpEngebLa6eoM/MpCpsE0ya7vm6f00=; b=KTw/CAUV+m9Xz13sE+TioqL9Ct KQvEL9OVLWbGtMmKtgduWHU5MPql07Xfl7jT7AQSHyznVcwHdgwQjJ0TbwmAyA40nLGEmT5EiHoM6 4gKwg8sV4hFPvvlng5WmTTBYK3PxVV7sZ6BAxzVwFMs7lUHsPnVHaYwH/Hssspt45eQLl9Y1fH1JE HIgh+blhj0FPbdtYm0o66RdLeotE+wLgx5U6Wr6Icwi+ua/e2jhMt/Ct/5bE0qe/lNjG6RT3yqJHc LbEuycmctZDAWdcE7/RCuSRn3lak9XMjFOvw2nZAAKT2l/a1LyUGbQrDkfqM5bg1d1yPvwbINni+j RoJnU/RQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wHnYa-000000027l6-2dR9; Tue, 28 Apr 2026 18:53:16 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wHnYZ-000000027kq-1bNr for linux-arm-kernel@lists.infradead.org; Tue, 28 Apr 2026 18:53:15 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 9CCD161145; Tue, 28 Apr 2026 18:53:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5CB64C2BCAF; Tue, 28 Apr 2026 18:53:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777402394; bh=FlAMEFJEBE2iSxVFssWyqGhfUZwzkv+yAAnIcO/A0hM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fr0DZHVXLIFaNzk6QY9sKFbSzma+VuuM/WUjgSXS4t2e7te5QsaB8yFahOTvPJLUw cawQv4QBkljkoWOnbzLea7yEns6mp2p/W3zxk1OnBJcTWNDpmwTZO5eWxPDsbTETQQ +KwxALHzGNo/A16ephqqgaAYPSqDQIa7E5BmdJYNdEWLi1SQI2YKRfIQTkegcpNqZ3 1o2Pw4mdgycPNwxK0CnPMi3+cPmecXlDangN/9yZstv/aKUZGXlsS8do11JyqxhKQ8 0x+Hk0OV5UVK7cXmm3qRDe4dlespmMNwN4gxowCBSEWaBmLQVE5GHMZiZ0topiIRvf 0vpK2+68XUWrQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Anshuman Khandual , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, "David Hildenbrand (Arm)" , Ryan Roberts , Catalin Marinas , Sasha Levin Subject: [PATCH 5.15.y] arm64/mm: Enable batched TLB flush in unmap_hotplug_range() Date: Tue, 28 Apr 2026 14:53:11 -0400 Message-ID: <20260428185311.3151505-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026042728-drier-spotty-9450@gregkh> References: <2026042728-drier-spotty-9450@gregkh> 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 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 --- arch/arm64/mm/mmu.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index e3e4defdea422..739d00a69be10 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -886,10 +886,14 @@ static void unmap_hotplug_pte_range(pmd_t *pmdp, unsigned long addr, 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); } @@ -910,15 +914,14 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr, 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)); @@ -943,15 +946,12 @@ static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr, 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)); @@ -981,6 +981,7 @@ static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr, 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; @@ -1002,6 +1003,9 @@ static void unmap_hotplug_range(unsigned long addr, unsigned long end, 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, -- 2.53.0