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Fri, 27 Oct 2023 11:22:45 -0700 (PDT) Date: Fri, 27 Oct 2023 11:21:52 -0700 In-Reply-To: <20231027182217.3615211-1-seanjc@google.com> Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> X-Mailer: git-send-email 2.42.0.820.g83a721a137-goog Message-ID: <20231027182217.3615211-11-seanjc@google.com> Subject: [PATCH v13 10/35] KVM: Add a dedicated mmu_notifier flag for reclaiming freed memory From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Sean Christopherson , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton Content-Type: text/plain; charset="UTF-8" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Sean Christopherson Cc: kvm@vger.kernel.org, David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chao Peng , linux-riscv@lists.infradead.org, Isaku Yamahata , Xiaoyao Li , Wang , Fuad Tabba , linux-arm-kernel@lists.infradead.org, Maciej Szmigiero , Michael Roth , Ackerley Tng , David Matlack , Vlastimil Babka , =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Isaku Yamahata , Quentin Perret , kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, Jarkko Sakkinen , Yu Zhang , "Kirill A . Shutemov" , kvm-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, Liam Merwick , Vishal Annapurve , linuxppc-dev@lists.ozlabs.org, Xu Yilun , Anish Moorthy Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Handle AMD SEV's kvm_arch_guest_memory_reclaimed() hook by having __kvm_handle_hva_range() return whether or not an overlapping memslot was found, i.e. mmu_lock was acquired. Using the .on_unlock() hook works, but kvm_arch_guest_memory_reclaimed() needs to run after dropping mmu_lock, which makes .on_lock() and .on_unlock() asymmetrical. Use a small struct to return the tuple of the notifier-specific return, plus whether or not overlap was found. Because the iteration helpers are __always_inlined, practically speaking, the struct will never actually be returned from a function call (not to mention the size of the struct will be two bytes in practice). Signed-off-by: Sean Christopherson --- virt/kvm/kvm_main.c | 53 +++++++++++++++++++++++++++++++-------------- 1 file changed, 37 insertions(+), 16 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 3f5b7c2c5327..2bc04c8ae1f4 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -561,6 +561,19 @@ struct kvm_mmu_notifier_range { bool may_block; }; +/* + * The inner-most helper returns a tuple containing the return value from the + * arch- and action-specific handler, plus a flag indicating whether or not at + * least one memslot was found, i.e. if the handler found guest memory. + * + * Note, most notifiers are averse to booleans, so even though KVM tracks the + * return from arch code as a bool, outer helpers will cast it to an int. :-( + */ +typedef struct kvm_mmu_notifier_return { + bool ret; + bool found_memslot; +} kvm_mn_ret_t; + /* * Use a dedicated stub instead of NULL to indicate that there is no callback * function/handler. The compiler technically can't guarantee that a real @@ -582,22 +595,25 @@ static const union kvm_mmu_notifier_arg KVM_MMU_NOTIFIER_NO_ARG; node; \ node = interval_tree_iter_next(node, start, last)) \ -static __always_inline int __kvm_handle_hva_range(struct kvm *kvm, - const struct kvm_mmu_notifier_range *range) +static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm, + const struct kvm_mmu_notifier_range *range) { - bool ret = false, locked = false; + struct kvm_mmu_notifier_return r = { + .ret = false, + .found_memslot = false, + }; struct kvm_gfn_range gfn_range; struct kvm_memory_slot *slot; struct kvm_memslots *slots; int i, idx; if (WARN_ON_ONCE(range->end <= range->start)) - return 0; + return r; /* A null handler is allowed if and only if on_lock() is provided. */ if (WARN_ON_ONCE(IS_KVM_NULL_FN(range->on_lock) && IS_KVM_NULL_FN(range->handler))) - return 0; + return r; idx = srcu_read_lock(&kvm->srcu); @@ -631,8 +647,8 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm, gfn_range.end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, slot); gfn_range.slot = slot; - if (!locked) { - locked = true; + if (!r.found_memslot) { + r.found_memslot = true; KVM_MMU_LOCK(kvm); if (!IS_KVM_NULL_FN(range->on_lock)) range->on_lock(kvm); @@ -640,14 +656,14 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm, if (IS_KVM_NULL_FN(range->handler)) break; } - ret |= range->handler(kvm, &gfn_range); + r.ret |= range->handler(kvm, &gfn_range); } } - if (range->flush_on_ret && ret) + if (range->flush_on_ret && r.ret) kvm_flush_remote_tlbs(kvm); - if (locked) { + if (r.found_memslot) { KVM_MMU_UNLOCK(kvm); if (!IS_KVM_NULL_FN(range->on_unlock)) range->on_unlock(kvm); @@ -655,8 +671,7 @@ static __always_inline int __kvm_handle_hva_range(struct kvm *kvm, srcu_read_unlock(&kvm->srcu, idx); - /* The notifiers are averse to booleans. :-( */ - return (int)ret; + return r; } static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn, @@ -677,7 +692,7 @@ static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn, .may_block = false, }; - return __kvm_handle_hva_range(kvm, &range); + return __kvm_handle_hva_range(kvm, &range).ret; } static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn, @@ -696,7 +711,7 @@ static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn .may_block = false, }; - return __kvm_handle_hva_range(kvm, &range); + return __kvm_handle_hva_range(kvm, &range).ret; } static bool kvm_change_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range) @@ -798,7 +813,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, .end = range->end, .handler = kvm_mmu_unmap_gfn_range, .on_lock = kvm_mmu_invalidate_begin, - .on_unlock = kvm_arch_guest_memory_reclaimed, + .on_unlock = (void *)kvm_null_fn, .flush_on_ret = true, .may_block = mmu_notifier_range_blockable(range), }; @@ -830,7 +845,13 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, gfn_to_pfn_cache_invalidate_start(kvm, range->start, range->end, hva_range.may_block); - __kvm_handle_hva_range(kvm, &hva_range); + /* + * If one or more memslots were found and thus zapped, notify arch code + * that guest memory has been reclaimed. This needs to be done *after* + * dropping mmu_lock, as x86's reclaim path is slooooow. + */ + if (__kvm_handle_hva_range(kvm, &hva_range).found_memslot) + kvm_arch_guest_memory_reclaimed(kvm); return 0; } -- 2.42.0.820.g83a721a137-goog