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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 , Michael Roth , mhocko@suse.com, wei.w.wang@intel.com Subject: Re: [PATCH v10 5/9] KVM: Use gfn instead of hva for mmu_notifier_retry Message-ID: <20221206115623.GB1216605@chaop.bj.intel.com> Reply-To: Chao Peng References: <20221202061347.1070246-1-chao.p.peng@linux.intel.com> <20221202061347.1070246-6-chao.p.peng@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9C5C9C0026 X-Stat-Signature: 9ymuhgcugbhg6iinriqi7sjtcm69m1s4 X-Spamd-Result: default: False [-5.70 / 9.00]; BAYES_HAM(-6.00)[100.00%]; SUBJECT_HAS_UNDERSCORES(1.00)[]; DMARC_POLICY_ALLOW(-0.50)[intel.com,none]; R_DKIM_ALLOW(-0.20)[intel.com:s=Intel]; MIME_GOOD(-0.10)[text/plain]; RCVD_NO_TLS_LAST(0.10)[]; RCPT_COUNT_TWELVE(0.00)[48]; R_SPF_NA(0.00)[no SPF record]; FROM_EQ_ENVFROM(0.00)[]; DKIM_TRACE(0.00)[intel.com:+]; MID_RHS_MATCH_FROMTLD(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; MIME_TRACE(0.00)[0:+]; FROM_HAS_DN(0.00)[]; REPLYTO_EQ_FROM(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_SOME(0.00)[]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; ARC_NA(0.00)[]; HAS_REPLYTO(0.00)[chao.p.peng@linux.intel.com] X-Rspam-User: X-HE-Tag: 1670328071-643689 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 Mon, Dec 05, 2022 at 09:23:49AM +0000, Fuad Tabba wrote: > Hi Chao, > > On Fri, Dec 2, 2022 at 6:19 AM Chao Peng wrote: > > > > Currently in mmu_notifier invalidate path, hva range is recorded and > > then checked against by mmu_notifier_retry_hva() in the page fault > > handling path. However, for the to be introduced private memory, a page > > fault may not have a hva associated, checking gfn(gpa) makes more sense. > > > > For existing hva based shared memory, gfn is expected to also work. The > > only downside is when aliasing multiple gfns to a single hva, the > > current algorithm of checking multiple ranges could result in a much > > larger range being rejected. Such aliasing should be uncommon, so the > > impact is expected small. > > > > Suggested-by: Sean Christopherson > > Signed-off-by: Chao Peng > > --- > > arch/x86/kvm/mmu/mmu.c | 8 +++++--- > > include/linux/kvm_host.h | 33 +++++++++++++++++++++------------ > > virt/kvm/kvm_main.c | 32 +++++++++++++++++++++++--------- > > 3 files changed, 49 insertions(+), 24 deletions(-) > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index 4736d7849c60..e2c70b5afa3e 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -4259,7 +4259,7 @@ static bool is_page_fault_stale(struct kvm_vcpu *vcpu, > > return true; > > > > return fault->slot && > > - mmu_invalidate_retry_hva(vcpu->kvm, mmu_seq, fault->hva); > > + mmu_invalidate_retry_gfn(vcpu->kvm, mmu_seq, fault->gfn); > > } > > > > static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) > > @@ -6098,7 +6098,9 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) > > > > write_lock(&kvm->mmu_lock); > > > > - kvm_mmu_invalidate_begin(kvm, gfn_start, gfn_end); > > + kvm_mmu_invalidate_begin(kvm); > > + > > + kvm_mmu_invalidate_range_add(kvm, gfn_start, gfn_end); > > > > flush = kvm_rmap_zap_gfn_range(kvm, gfn_start, gfn_end); > > > > @@ -6112,7 +6114,7 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) > > kvm_flush_remote_tlbs_with_address(kvm, gfn_start, > > gfn_end - gfn_start); > > > > - kvm_mmu_invalidate_end(kvm, gfn_start, gfn_end); > > + kvm_mmu_invalidate_end(kvm); > > > > write_unlock(&kvm->mmu_lock); > > } > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 02347e386ea2..3d69484d2704 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -787,8 +787,8 @@ struct kvm { > > struct mmu_notifier mmu_notifier; > > unsigned long mmu_invalidate_seq; > > long mmu_invalidate_in_progress; > > - unsigned long mmu_invalidate_range_start; > > - unsigned long mmu_invalidate_range_end; > > + gfn_t mmu_invalidate_range_start; > > + gfn_t mmu_invalidate_range_end; > > #endif > > struct list_head devices; > > u64 manual_dirty_log_protect; > > @@ -1389,10 +1389,9 @@ void kvm_mmu_free_memory_cache(struct kvm_mmu_memory_cache *mc); > > void *kvm_mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc); > > #endif > > > > -void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start, > > - unsigned long end); > > -void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start, > > - unsigned long end); > > +void kvm_mmu_invalidate_begin(struct kvm *kvm); > > +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end); > > +void kvm_mmu_invalidate_end(struct kvm *kvm); > > > > long kvm_arch_dev_ioctl(struct file *filp, > > unsigned int ioctl, unsigned long arg); > > @@ -1963,9 +1962,9 @@ static inline int mmu_invalidate_retry(struct kvm *kvm, unsigned long mmu_seq) > > return 0; > > } > > > > -static inline int mmu_invalidate_retry_hva(struct kvm *kvm, > > +static inline int mmu_invalidate_retry_gfn(struct kvm *kvm, > > unsigned long mmu_seq, > > - unsigned long hva) > > + gfn_t gfn) > > { > > lockdep_assert_held(&kvm->mmu_lock); > > /* > > @@ -1974,10 +1973,20 @@ static inline int mmu_invalidate_retry_hva(struct kvm *kvm, > > * that might be being invalidated. Note that it may include some false > > nit: "might be" (or) "is being" > > > * positives, due to shortcuts when handing concurrent invalidations. > > nit: handling Both are existing code, but I can fix it either. > > > */ > > - if (unlikely(kvm->mmu_invalidate_in_progress) && > > - hva >= kvm->mmu_invalidate_range_start && > > - hva < kvm->mmu_invalidate_range_end) > > - return 1; > > + if (unlikely(kvm->mmu_invalidate_in_progress)) { > > + /* > > + * Dropping mmu_lock after bumping mmu_invalidate_in_progress > > + * but before updating the range is a KVM bug. > > + */ > > + if (WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA || > > + kvm->mmu_invalidate_range_end == INVALID_GPA)) > > INVALID_GPA is an x86-specific define in > arch/x86/include/asm/kvm_host.h, so this doesn't build on other > architectures. The obvious fix is to move it to > include/linux/kvm_host.h. Hmm, INVALID_GPA is defined as ZERO for x86, not 100% confident this is correct choice for other architectures, but after search it has not been used for other architectures, so should be safe to make it common. Thanks, Chao > > Cheers, > /fuad > > > + return 1; > > + > > + if (gfn >= kvm->mmu_invalidate_range_start && > > + gfn < kvm->mmu_invalidate_range_end) > > + return 1; > > + } > > + > > if (kvm->mmu_invalidate_seq != mmu_seq) > > return 1; > > return 0; > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index b882eb2c76a2..ad55dfbc75d7 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -540,9 +540,7 @@ static void kvm_mmu_notifier_invalidate_range(struct mmu_notifier *mn, > > > > typedef bool (*hva_handler_t)(struct kvm *kvm, struct kvm_gfn_range *range); > > > > -typedef void (*on_lock_fn_t)(struct kvm *kvm, unsigned long start, > > - unsigned long end); > > - > > +typedef void (*on_lock_fn_t)(struct kvm *kvm); > > typedef void (*on_unlock_fn_t)(struct kvm *kvm); > > > > struct kvm_hva_range { > > @@ -628,7 +626,8 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm, > > locked = true; > > KVM_MMU_LOCK(kvm); > > if (!IS_KVM_NULL_FN(range->on_lock)) > > - range->on_lock(kvm, range->start, range->end); > > + range->on_lock(kvm); > > + > > if (IS_KVM_NULL_FN(range->handler)) > > break; > > } > > @@ -715,8 +714,7 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn, > > kvm_handle_hva_range(mn, address, address + 1, pte, kvm_set_spte_gfn); > > } > > > > -void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start, > > - unsigned long end) > > +void kvm_mmu_invalidate_begin(struct kvm *kvm) > > { > > /* > > * The count increase must become visible at unlock time as no > > @@ -724,6 +722,17 @@ void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start, > > * count is also read inside the mmu_lock critical section. > > */ > > kvm->mmu_invalidate_in_progress++; > > + > > + if (likely(kvm->mmu_invalidate_in_progress == 1)) { > > + kvm->mmu_invalidate_range_start = INVALID_GPA; > > + kvm->mmu_invalidate_range_end = INVALID_GPA; > > + } > > +} > > + > > +void kvm_mmu_invalidate_range_add(struct kvm *kvm, gfn_t start, gfn_t end) > > +{ > > + WARN_ON_ONCE(!kvm->mmu_invalidate_in_progress); > > + > > if (likely(kvm->mmu_invalidate_in_progress == 1)) { > > kvm->mmu_invalidate_range_start = start; > > kvm->mmu_invalidate_range_end = end; > > @@ -744,6 +753,12 @@ void kvm_mmu_invalidate_begin(struct kvm *kvm, unsigned long start, > > } > > } > > > > +static bool kvm_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range) > > +{ > > + kvm_mmu_invalidate_range_add(kvm, range->start, range->end); > > + return kvm_unmap_gfn_range(kvm, range); > > +} > > + > > static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, > > const struct mmu_notifier_range *range) > > { > > @@ -752,7 +767,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, > > .start = range->start, > > .end = range->end, > > .pte = __pte(0), > > - .handler = kvm_unmap_gfn_range, > > + .handler = kvm_mmu_unmap_gfn_range, > > .on_lock = kvm_mmu_invalidate_begin, > > .on_unlock = kvm_arch_guest_memory_reclaimed, > > .flush_on_ret = true, > > @@ -791,8 +806,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, > > return 0; > > } > > > > -void kvm_mmu_invalidate_end(struct kvm *kvm, unsigned long start, > > - unsigned long end) > > +void kvm_mmu_invalidate_end(struct kvm *kvm) > > { > > /* > > * This sequence increase will notify the kvm page fault that > > -- > > 2.25.1 > >