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Sun, 5 Nov 2023 16:31:58 +0000 (UTC) From: Paolo Bonzini 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 Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A. Shutemov" Subject: [PATCH 10/34] KVM: Add a dedicated mmu_notifier flag for reclaiming freed memory Date: Sun, 5 Nov 2023 17:30:13 +0100 Message-ID: <20231105163040.14904-11-pbonzini@redhat.com> In-Reply-To: <20231105163040.14904-1-pbonzini@redhat.com> References: <20231105163040.14904-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 X-Rspamd-Queue-Id: 493D2140025 X-Rspam-User: X-Stat-Signature: bn54owc9aji8j1ubyertcuo4skbgx57f X-Rspamd-Server: rspam01 X-HE-Tag: 1699201930-91904 X-HE-Meta: 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 XahTS/3r eNCGWsiWXTXCg3g27KAY7z53Gw76sCplvJx3bvxi8GHyKOVOwcsWZtzXiV7J3Y8E+3AsGtDylEpi/vwjPn/ymuNDP/eD3pGPTrNoMiuKuKhiSlRQYWHsp/cvpwzd20G9lI0wF4Z8jOlgsV4R9U3I0iHFNIyX9Kx3WIeLhhXapdgbvT3h1wi2ELc9Jwi1itQSDzait7FmFsJIhyeC99t+23V49xo35wFgsR6uuhz7aYj4zyrZpCumXJymYDlrLmWwMJE7xevcNl1NwsldkKhEFPCo93pPhOfK7M3vfyiV+k60b7YMkv0WTR1YEHs2+fwKnfW5X 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: List-Subscribe: List-Unsubscribe: From: Sean Christopherson 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 Reviewed-by: Paolo Bonzini Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Message-Id: <20231027182217.3615211-11-seanjc@google.com> Signed-off-by: Paolo Bonzini --- 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 756b94ecd511..e18a7f152c0b 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; } -- 2.39.1