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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 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1669023169; a=rsa-sha256; cv=none; b=PyJUnwN95tSysuVFWYMB3vyPIg7OmUjdIFXyUzTPkUCyr+9UK3PmZ6uzcyzjY6zTqxOyST /syE7XkbO0XdpG+PD+PpcgMYfmHwvYpO4epxqE9NIijk14EqsOMeujJx7cwQbUIM0ipHmh G/t1/f6GF3xLj3Y7APe2Wa0hkVjlBbg= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=pCaLAKPO; spf=pass (imf30.hostedemail.com: domain of jgross@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=jgross@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1669023169; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:references:dkim-signature; bh=+IB1aGd/z1BLz0hR/u2GFVPc2+6aTfO3p/KLk/OY+YQ=; b=OlAO8lOjxPJt87PRw5Sp0CyyVwqYJBE6urbQwYSE2OWOiDkt4WHrO8SbVXZzj2kGHmeLtc qKz+ssY5C1rQcHFVdGT/kCPg5c3TsXABlJ3klDo9zDTv9qM9frcX4qtgG+Y0A/KAUxth8a L9eb1AVUM6q9EoK7adgmkMrVWG8wtC0= Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=pCaLAKPO; spf=pass (imf30.hostedemail.com: domain of jgross@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=jgross@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: AAD6680008 X-Rspam-User: X-Stat-Signature: smncd7shq5suj4jcpjw3qk9ittxescc3 X-HE-Tag: 1669023168-938746 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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; } +#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_area_struct *vma, #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif +#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, unsigned long next, struct vm_area goto next; 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 long start, unsigned long end, #endif walk->mm_stats[MM_NONLEAF_TOTAL]++; -#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; 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; @@ -5354,7 +5354,7 @@ static ssize_t show_enabled(struct kobject *kobj, struct kobj_attribute *attr, c if (arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK)) caps |= BIT(LRU_GEN_MM_WALK); - if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) && get_cap(LRU_GEN_NONLEAF_YOUNG)) + if (arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG)) caps |= BIT(LRU_GEN_NONLEAF_YOUNG); return snprintf(buf, PAGE_SIZE, "0x%04x\n", caps);