From nobody Wed Apr 15 19:44:03 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54E49C4332F for ; Mon, 21 Nov 2022 09:32:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230238AbiKUJcz (ORCPT ); Mon, 21 Nov 2022 04:32:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44676 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229755AbiKUJcu (ORCPT ); Mon, 21 Nov 2022 04:32:50 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 446A15FDD for ; Mon, 21 Nov 2022 01:32:48 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 83955220C5; Mon, 21 Nov 2022 09:32:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1669023167; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=+IB1aGd/z1BLz0hR/u2GFVPc2+6aTfO3p/KLk/OY+YQ=; b=pCaLAKPOadyM9JJ2sgJI1rBx0795xJMSOizZLNSwLEKuNpy5sOfX6AS+wb9kk5eBocQZex bN5x7UxAyhY54FFb1BAxOVH8RPb7xhOTeJPaMRmDvK51JVTwB/6gISLHipB5WAtpwgPhG4 Yc8DNfXDEJw2KOENjAqINFYwEFHJhfg= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 1C4851377F; Mon, 21 Nov 2022 09:32:47 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 0wk5Bb9Fe2OPbwAAMHmgww (envelope-from ); Mon, 21 Nov 2022 09:32:47 +0000 From: Juergen Gross To: linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org Cc: yuzhao@google.com, Juergen Gross , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andrew Morton , Sander Eikelenboom Subject: [PATCH] mm: introduce arch_has_hw_pmd_young() Date: Mon, 21 Nov 2022 10:32:45 +0100 Message-Id: <20221121093245.4587-1-jgross@suse.com> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When running as a Xen PV guests commit eed9a328aa1a ("mm: x86: add CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG") can cause a protection violation in pmdp_test_and_clear_young(): BUG: unable to handle page fault for address: ffff8880083374d0 #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 3026067 P4D 3026067 PUD 3027067 PMD 7fee5067 PTE 8010000008337065 Oops: 0003 [#1] PREEMPT SMP NOPTI CPU: 7 PID: 158 Comm: kswapd0 Not tainted 6.1.0-rc5-20221118-doflr+ #1 RIP: e030:pmdp_test_and_clear_young+0x25/0x40 This happens because the Xen hypervisor can't emulate direct writes to page table entries other than PTEs. This can easily be fixed by introducing arch_has_hw_pmd_young() similar to arch_has_hw_pte_young() and test that instead of CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG. Fixes: eed9a328aa1a ("mm: x86: add CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG") Reported-by: Sander Eikelenboom Signed-off-by: Juergen Gross Acked-by: Yu Zhao --- arch/x86/include/asm/pgtable.h | 8 ++++++++ include/linux/pgtable.h | 11 +++++++++++ mm/vmscan.c | 10 +++++----- 3 files changed, 24 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 5059799bebe3..c567a6ed17ce 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1438,6 +1438,14 @@ static inline bool arch_has_hw_pte_young(void) return true; } =20 +#ifdef CONFIG_XEN_PV +#define arch_has_hw_nonleaf_pmd_young arch_has_hw_nonleaf_pmd_young +static inline bool arch_has_hw_nonleaf_pmd_young(void) +{ + return !cpu_feature_enabled(X86_FEATURE_XENPV); +} +#endif + #ifdef CONFIG_PAGE_TABLE_CHECK static inline bool pte_user_accessible_page(pte_t pte) { diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index a108b60a6962..58fc7e2d9575 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -260,6 +260,17 @@ static inline int pmdp_clear_flush_young(struct vm_are= a_struct *vma, #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif =20 +#ifndef arch_has_hw_nonleaf_pmd_young +/* + * Return whether the accessed bit in non-leaf PMD entries is supported on= the + * local CPU. + */ +static inline bool arch_has_hw_nonleaf_pmd_young(void) +{ + return IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG); +} +#endif + #ifndef arch_has_hw_pte_young /* * Return whether the accessed bit is supported on the local CPU. diff --git a/mm/vmscan.c b/mm/vmscan.c index 04d8b88e5216..a04ac3b18326 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3975,7 +3975,7 @@ static void walk_pmd_range_locked(pud_t *pud, unsigne= d long next, struct vm_area goto next; =20 if (!pmd_trans_huge(pmd[i])) { - if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) && + if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG)) pmdp_test_and_clear_young(vma, addr, pmd + i); goto next; @@ -4073,14 +4073,14 @@ static void walk_pmd_range(pud_t *pud, unsigned lon= g start, unsigned long end, #endif walk->mm_stats[MM_NONLEAF_TOTAL]++; =20 -#ifdef CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG - if (get_cap(LRU_GEN_NONLEAF_YOUNG)) { + if (arch_has_hw_nonleaf_pmd_young() && + get_cap(LRU_GEN_NONLEAF_YOUNG)) { if (!pmd_young(val)) continue; =20 walk_pmd_range_locked(pud, addr, vma, args, bitmap, &pos); } -#endif + if (!walk->force_scan && !test_bloom_filter(walk->lruvec, walk->max_seq,= pmd + i)) continue; =20 @@ -5354,7 +5354,7 @@ static ssize_t show_enabled(struct kobject *kobj, str= uct kobj_attribute *attr, c if (arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK)) caps |=3D BIT(LRU_GEN_MM_WALK); =20 - if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) && get_cap(LRU_GEN_NONL= EAF_YOUNG)) + if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG)) caps |=3D BIT(LRU_GEN_NONLEAF_YOUNG); =20 return snprintf(buf, PAGE_SIZE, "0x%04x\n", caps); --=20 2.35.3