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Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Shuah Khan , Mike Rapoport , Steven Price , "Maciej S . Szmigiero" , Vlastimil Babka , Vishal Annapurve , Yu Zhang , "Kirill A . Shutemov" , luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com, aarcange@redhat.com, ddutile@redhat.com, dhildenb@redhat.com, Quentin Perret , tabba@google.com, Michael Roth , mhocko@suse.com, Muchun Song , wei.w.wang@intel.com, isaku.yamahata@gmail.com Subject: Re: [PATCH v9 6/8] KVM: Update lpage info when private/shared memory are mixed Message-ID: <20221026204620.GB3819453@ls.amr.corp.intel.com> References: <20221025151344.3784230-1-chao.p.peng@linux.intel.com> <20221025151344.3784230-7-chao.p.peng@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221025151344.3784230-7-chao.p.peng@linux.intel.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666817183; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=osbqX8leV6g/SkiEHlFgEuxy7LRzWU2Y7Uh+l7tX15w=; b=KF0mMu+yrUPVK8JAjW3bOX81XlfvgKGDxd/KrTmhpoOZtDobMNSGkyBtBdq1i3C8IzUx+Q QBMjExnfs/qnUqcuIQ5BU4jAem0uRGPxYGGqi4+bIAPPHT8VybavBpJd6/bVYBOY78cTMa tft56ADYIdciT0Te6X79yXZ15nO6KWg= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=jpYjPBLG; spf=pass (imf06.hostedemail.com: domain of isaku.yamahata@gmail.com designates 209.85.214.174 as permitted sender) smtp.mailfrom=isaku.yamahata@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666817183; a=rsa-sha256; cv=none; b=4H151G0o5MAoo5xyJStvjFiZic76inxiMjv7IV519XDvSgRVOgFjtZ8dnWRc7x7Yj9zmvG BIa6cYsfmEP8rgXx0R1y2R5hdLm8g4AFzrMQfFOeZx6jz2E4d5KrifzBuyXr5Q63Iw7MTV JijdDfapOCnif2CEnF7YUU5w1UBoTLA= Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=jpYjPBLG; spf=pass (imf06.hostedemail.com: domain of isaku.yamahata@gmail.com designates 209.85.214.174 as permitted sender) smtp.mailfrom=isaku.yamahata@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: rasq9jo3843ajqr8yc8qgta5zzd5n4a9 X-Rspamd-Queue-Id: 8E45418003C X-Rspamd-Server: rspam07 X-Rspam-User: X-HE-Tag: 1666817183-433185 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 Tue, Oct 25, 2022 at 11:13:42PM +0800, Chao Peng wrote: > When private/shared memory are mixed in a large page, the lpage_info may > not be accurate and should be updated with this mixed info. A large page > has mixed pages can't be really mapped as large page since its > private/shared pages are from different physical memory. > > Update lpage_info when private/shared memory attribute is changed. If > both private and shared pages are within a large page region, it can't > be mapped as large page. It's a bit challenge to track the mixed > info in a 'count' like variable, this patch instead reserves a bit in > 'disallow_lpage' to indicate a large page has mixed private/share pages. > > Signed-off-by: Chao Peng > --- > arch/x86/include/asm/kvm_host.h | 8 +++ > arch/x86/kvm/mmu/mmu.c | 112 +++++++++++++++++++++++++++++++- > arch/x86/kvm/x86.c | 2 + > include/linux/kvm_host.h | 19 ++++++ > virt/kvm/kvm_main.c | 16 +++-- > 5 files changed, 152 insertions(+), 5 deletions(-) > ... > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 33b1aec44fb8..67a9823a8c35 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c ... > @@ -6910,3 +6915,108 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm) > if (kvm->arch.nx_lpage_recovery_thread) > kthread_stop(kvm->arch.nx_lpage_recovery_thread); > } > + > +static inline bool linfo_is_mixed(struct kvm_lpage_info *linfo) > +{ > + return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED; > +} > + > +static inline void linfo_update_mixed(struct kvm_lpage_info *linfo, bool mixed) > +{ > + if (mixed) > + linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED; > + else > + linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED; > +} > + > +static bool mem_attr_is_mixed_2m(struct kvm *kvm, unsigned int attr, > + gfn_t start, gfn_t end) > +{ > + XA_STATE(xas, &kvm->mem_attr_array, start); > + gfn_t gfn = start; > + void *entry; > + bool shared = attr == KVM_MEM_ATTR_SHARED; > + bool mixed = false; > + > + rcu_read_lock(); > + entry = xas_load(&xas); > + while (gfn < end) { > + if (xas_retry(&xas, entry)) > + continue; > + > + KVM_BUG_ON(gfn != xas.xa_index, kvm); > + > + if ((entry && !shared) || (!entry && shared)) { > + mixed = true; > + goto out; nitpick: goto isn't needed. break should work. > + } > + > + entry = xas_next(&xas); > + gfn++; > + } > +out: > + rcu_read_unlock(); > + return mixed; > +} > + > +static bool mem_attr_is_mixed(struct kvm *kvm, struct kvm_memory_slot *slot, > + int level, unsigned int attr, > + gfn_t start, gfn_t end) > +{ > + unsigned long gfn; > + void *entry; > + > + if (level == PG_LEVEL_2M) > + return mem_attr_is_mixed_2m(kvm, attr, start, end); > + > + entry = xa_load(&kvm->mem_attr_array, start); > + for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) { > + if (linfo_is_mixed(lpage_info_slot(gfn, slot, level - 1))) > + return true; > + if (xa_load(&kvm->mem_attr_array, gfn) != entry) > + return true; > + } > + return false; > +} > + > +void kvm_arch_update_mem_attr(struct kvm *kvm, struct kvm_memory_slot *slot, > + unsigned int attr, gfn_t start, gfn_t end) > +{ > + > + unsigned long lpage_start, lpage_end; > + unsigned long gfn, pages, mask; > + int level; > + > + WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)), > + "Unsupported mem attribute.\n"); > + > + /* > + * The sequence matters here: we update the higher level basing on the > + * lower level's scanning result. > + */ > + for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) { > + pages = KVM_PAGES_PER_HPAGE(level); > + mask = ~(pages - 1); nitpick: KVM_HPAGE_MASK(level). Maybe matter of preference. > + lpage_start = max(start & mask, slot->base_gfn); > + lpage_end = (end - 1) & mask; > + > + /* > + * We only need to scan the head and tail page, for middle pages > + * we know they are not mixed. > + */ > + linfo_update_mixed(lpage_info_slot(lpage_start, slot, level), > + mem_attr_is_mixed(kvm, slot, level, attr, > + lpage_start, start)); > + > + if (lpage_start == lpage_end) > + return; > + > + for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages) > + linfo_update_mixed(lpage_info_slot(gfn, slot, level), > + false); > + > + linfo_update_mixed(lpage_info_slot(lpage_end, slot, level), > + mem_attr_is_mixed(kvm, slot, level, attr, > + end, lpage_end + pages)); > + } > +} -- Isaku Yamahata