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AJvYcCUDvES5+ryJHH1equ9sXT55ZfC8qaxHbTlfznBwC/LC9bnbf9zqgIGQg46rF81VJOp8/6HDdhfZNg==@kvack.org X-Gm-Message-State: AOJu0YwIjL9IS1UXh4xfYz6M/ZO2aJwa6cVxyvSsm+oG/Qk3KBAndrZM ImJ3tkmhAlb85cF/5I/jvtwB/8fUxDQNWi6V3/sfyV+awUMVjZLAENb4xCj7/teepmm2T7ODHk5 b3RIeBGOrskcmV4Vh1Q== X-Google-Smtp-Source: AGHT+IGaRNcJ0pUCHmWao5UQiFUuGRcX2zXYa1voIITtc2canA4FkWeSC7N08ZTT/PlEa6ZAuN210z4HqmS+Jzo6 X-Received: from jthoughton.c.googlers.com ([fda3:e722:ac3:cc00:13d:fb22:ac12:a84b]) (user=jthoughton job=sendgmr) by 2002:a25:d608:0:b0:e11:6a73:b0d with SMTP id 3f1490d57ef6-e24d9dc640bmr3172276.6.1727314523065; Wed, 25 Sep 2024 18:35:23 -0700 (PDT) Date: Thu, 26 Sep 2024 01:34:55 +0000 In-Reply-To: <20240926013506.860253-1-jthoughton@google.com> Mime-Version: 1.0 References: <20240926013506.860253-1-jthoughton@google.com> X-Mailer: git-send-email 2.46.0.792.g87dc391469-goog Message-ID: <20240926013506.860253-8-jthoughton@google.com> Subject: [PATCH v7 07/18] KVM: x86/mmu: Refactor low level rmap helpers to prep for walking w/o mmu_lock From: James Houghton To: Sean Christopherson , Paolo Bonzini Cc: Andrew Morton , David Matlack , David Rientjes , James Houghton , Jason Gunthorpe , Jonathan Corbet , Marc Zyngier , Oliver Upton , Wei Xu , Yu Zhao , Axel Rasmussen , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: AE15E180007 X-Stat-Signature: 43361yjgupkxixgmtc1596ah1tu98u8z X-Rspam-User: X-HE-Tag: 1727314524-374814 X-HE-Meta: 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 l8G50bMI 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Sean Christopherson Refactor the pte_list and rmap code to always read and write rmap_head->val exactly once, e.g. by collecting changes in a local variable and then propagating those changes back to rmap_head->val as appropriate. This will allow implementing a per-rmap rwlock (of sorts) by adding a LOCKED bit into the rmap value alongside the MANY bit. Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 83 +++++++++++++++++++++++++----------------- 1 file changed, 50 insertions(+), 33 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index b4e543bdf3f0..17de470f542c 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -920,21 +920,24 @@ static struct kvm_memory_slot *gfn_to_memslot_dirty_bitmap(struct kvm_vcpu *vcpu static int pte_list_add(struct kvm_mmu_memory_cache *cache, u64 *spte, struct kvm_rmap_head *rmap_head) { + unsigned long old_val, new_val; struct pte_list_desc *desc; int count = 0; - if (!rmap_head->val) { - rmap_head->val = (unsigned long)spte; - } else if (!(rmap_head->val & KVM_RMAP_MANY)) { + old_val = rmap_head->val; + + if (!old_val) { + new_val = (unsigned long)spte; + } else if (!(old_val & KVM_RMAP_MANY)) { desc = kvm_mmu_memory_cache_alloc(cache); - desc->sptes[0] = (u64 *)rmap_head->val; + desc->sptes[0] = (u64 *)old_val; desc->sptes[1] = spte; desc->spte_count = 2; desc->tail_count = 0; - rmap_head->val = (unsigned long)desc | KVM_RMAP_MANY; + new_val = (unsigned long)desc | KVM_RMAP_MANY; ++count; } else { - desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); + desc = (struct pte_list_desc *)(old_val & ~KVM_RMAP_MANY); count = desc->tail_count + desc->spte_count; /* @@ -943,21 +946,25 @@ static int pte_list_add(struct kvm_mmu_memory_cache *cache, u64 *spte, */ if (desc->spte_count == PTE_LIST_EXT) { desc = kvm_mmu_memory_cache_alloc(cache); - desc->more = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); + desc->more = (struct pte_list_desc *)(old_val & ~KVM_RMAP_MANY); desc->spte_count = 0; desc->tail_count = count; - rmap_head->val = (unsigned long)desc | KVM_RMAP_MANY; + new_val = (unsigned long)desc | KVM_RMAP_MANY; + } else { + new_val = old_val; } desc->sptes[desc->spte_count++] = spte; } + + rmap_head->val = new_val; + return count; } -static void pte_list_desc_remove_entry(struct kvm *kvm, - struct kvm_rmap_head *rmap_head, +static void pte_list_desc_remove_entry(struct kvm *kvm, unsigned long *rmap_val, struct pte_list_desc *desc, int i) { - struct pte_list_desc *head_desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); + struct pte_list_desc *head_desc = (struct pte_list_desc *)(*rmap_val & ~KVM_RMAP_MANY); int j = head_desc->spte_count - 1; /* @@ -984,9 +991,9 @@ static void pte_list_desc_remove_entry(struct kvm *kvm, * head at the next descriptor, i.e. the new head. */ if (!head_desc->more) - rmap_head->val = 0; + *rmap_val = 0; else - rmap_head->val = (unsigned long)head_desc->more | KVM_RMAP_MANY; + *rmap_val = (unsigned long)head_desc->more | KVM_RMAP_MANY; mmu_free_pte_list_desc(head_desc); } @@ -994,24 +1001,26 @@ static void pte_list_remove(struct kvm *kvm, u64 *spte, struct kvm_rmap_head *rmap_head) { struct pte_list_desc *desc; + unsigned long rmap_val; int i; - if (KVM_BUG_ON_DATA_CORRUPTION(!rmap_head->val, kvm)) - return; + rmap_val = rmap_head->val; + if (KVM_BUG_ON_DATA_CORRUPTION(!rmap_val, kvm)) + goto out; - if (!(rmap_head->val & KVM_RMAP_MANY)) { - if (KVM_BUG_ON_DATA_CORRUPTION((u64 *)rmap_head->val != spte, kvm)) - return; + if (!(rmap_val & KVM_RMAP_MANY)) { + if (KVM_BUG_ON_DATA_CORRUPTION((u64 *)rmap_val != spte, kvm)) + goto out; - rmap_head->val = 0; + rmap_val = 0; } else { - desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); + desc = (struct pte_list_desc *)(rmap_val & ~KVM_RMAP_MANY); while (desc) { for (i = 0; i < desc->spte_count; ++i) { if (desc->sptes[i] == spte) { - pte_list_desc_remove_entry(kvm, rmap_head, + pte_list_desc_remove_entry(kvm, &rmap_val, desc, i); - return; + goto out; } } desc = desc->more; @@ -1019,6 +1028,9 @@ static void pte_list_remove(struct kvm *kvm, u64 *spte, KVM_BUG_ON_DATA_CORRUPTION(true, kvm); } + +out: + rmap_head->val = rmap_val; } static void kvm_zap_one_rmap_spte(struct kvm *kvm, @@ -1033,17 +1045,19 @@ static bool kvm_zap_all_rmap_sptes(struct kvm *kvm, struct kvm_rmap_head *rmap_head) { struct pte_list_desc *desc, *next; + unsigned long rmap_val; int i; - if (!rmap_head->val) + rmap_val = rmap_head->val; + if (!rmap_val) return false; - if (!(rmap_head->val & KVM_RMAP_MANY)) { - mmu_spte_clear_track_bits(kvm, (u64 *)rmap_head->val); + if (!(rmap_val & KVM_RMAP_MANY)) { + mmu_spte_clear_track_bits(kvm, (u64 *)rmap_val); goto out; } - desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); + desc = (struct pte_list_desc *)(rmap_val & ~KVM_RMAP_MANY); for (; desc; desc = next) { for (i = 0; i < desc->spte_count; i++) @@ -1059,14 +1073,15 @@ static bool kvm_zap_all_rmap_sptes(struct kvm *kvm, unsigned int pte_list_count(struct kvm_rmap_head *rmap_head) { + unsigned long rmap_val = rmap_head->val; struct pte_list_desc *desc; - if (!rmap_head->val) + if (!rmap_val) return 0; - else if (!(rmap_head->val & KVM_RMAP_MANY)) + else if (!(rmap_val & KVM_RMAP_MANY)) return 1; - desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); + desc = (struct pte_list_desc *)(rmap_val & ~KVM_RMAP_MANY); return desc->tail_count + desc->spte_count; } @@ -1109,6 +1124,7 @@ static void rmap_remove(struct kvm *kvm, u64 *spte) */ struct rmap_iterator { /* private fields */ + struct rmap_head *head; struct pte_list_desc *desc; /* holds the sptep if not NULL */ int pos; /* index of the sptep */ }; @@ -1123,18 +1139,19 @@ struct rmap_iterator { static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head, struct rmap_iterator *iter) { + unsigned long rmap_val = rmap_head->val; u64 *sptep; - if (!rmap_head->val) + if (!rmap_val) return NULL; - if (!(rmap_head->val & KVM_RMAP_MANY)) { + if (!(rmap_val & KVM_RMAP_MANY)) { iter->desc = NULL; - sptep = (u64 *)rmap_head->val; + sptep = (u64 *)rmap_val; goto out; } - iter->desc = (struct pte_list_desc *)(rmap_head->val & ~KVM_RMAP_MANY); + iter->desc = (struct pte_list_desc *)(rmap_val & ~KVM_RMAP_MANY); iter->pos = 0; sptep = iter->desc->sptes[iter->pos]; out: