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(p200300cbc7049f00a98d40267c4440fd.dip0.t-ipconnect.de. [2003:cb:c704:9f00:a98d:4026:7c44:40fd]) by smtp.gmail.com with ESMTPSA id f19-20020a05600c44d300b003c6b70a4d69sm1474406wmo.42.2022.11.23.01.31.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Nov 2022 01:31:09 -0800 (PST) Message-ID: <33cfb5ea-1253-430a-0ed9-a84174bc6fdd@redhat.com> Date: Wed, 23 Nov 2022 10:31:08 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH v2] mm: introduce arch_has_hw_nonleaf_pmd_young() To: Juergen Gross , linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andrew Morton , Sander Eikelenboom , Yu Zhao References: <20221123064510.16225-1-jgross@suse.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20221123064510.16225-1-jgross@suse.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1669195873; a=rsa-sha256; cv=none; b=rKOB2tpx2PeoFfNn+CbqWonhnVDxr74Xy/dC81xUrwKcZy8XE2em8a629pXA9sjIUNTb4h KbzD4T2loU04/z9OxIzigfZ9vE1Ww2Sn4g5MbcO7TccHcQ+K7tGOeES3bEHpb76/LASy7W TwZAIqOlPiZqs7Qn9hQ+Z/gNlQ2R74E= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=SdJZGyWx; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf04.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1669195873; 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-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=l0tP8BFuS7YQvcxcgs/n+rozp/L98Njww9kvIfR3QxA=; b=JcyWESHVI7Bcp/uiGzDpBIC645efx5br83mqIRBx62knX9aMPvc8izYagtwGusLTBNyTWb G6REMuKiv3FF5PBH1NpxratkvEC1POCt7taVyjSr3EdcRosx2hRgNWXlKbKQkwsBlZ36Ja wKP33voqkHvlY2iAt0TnqRJZoW1bgYQ= Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=SdJZGyWx; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf04.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com X-Stat-Signature: 18bgt7jtdbdz9j4rbz1p1uzdtuybkhaz X-Rspamd-Queue-Id: 6169440009 X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1669195873-778409 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: On 23.11.22 07:45, Juergen Gross wrote: > 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_nonleaf_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 > Tested-by: Sander Eikelenboom > --- > V2: > - correct function name in commit message to match patch > --- > 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); Acked-by: David Hildenbrand # core changes -- Thanks, David / dhildenb