From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C32232D94A9 for ; Tue, 15 Jul 2025 09:34:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752572054; cv=none; b=KRVmtoYwCSCnAFw/pHstDH7Dtp7en8BbcDDQh0YNKQb9BrOu9udRbUaa6K8mBmPPXvAFuubw17cUHE2DmCyLWOKTAXAEuH7Q56rRqqA7grk6ixDR7qCH6vihh7FeH3QmJ377ECBbfWXqpxNWqCyXxjFQcXSqoIF5lkePM4fRAkA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752572054; c=relaxed/simple; bh=rwFpQdz+xqsV9TRx7fn+9BFSSTMO137zIdaSVB+FJjM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=X5RG9khEN8mLSZVO+bOQhMBnI4+xtJUHqxKzjoGUDNFTJrFAQBN7l6962blnrHEYBUGNu3r1+dXlEcUW9/KUkWxeKstqCZCpmbXaHbIhTllhZt9xbVGYxqPiWmiqlfpVlmEPgmuzw/epwkmoLrxMbxDAU+L+w1mkOK3TKK2VVtM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--tabba.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=amOVj5do; arc=none smtp.client-ip=209.85.128.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--tabba.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="amOVj5do" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-4560b81ff9eso18482625e9.1 for ; Tue, 15 Jul 2025 02:34:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1752572051; x=1753176851; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=HKm1OPddzPOCVybWQJf7fIOws1hHLUPbnC0KechHFr4=; b=amOVj5doke0jR5KbSOkqnIedeIeCu+k7cCqhFHGXnmfHP4KNkN9YayNLbFW0DRiHJx ilGYaWYpunrYyjaTEdwjZQOo9hc89LrLNfaHNuIIaPJa3sbbWpHUO7TpmSrkNt70GwbI jlYQBeCCQNDY1MrIBqApay60uOvHuCdxtbREL34YR4nh+ElLSl9FxWKfxW164jhpkHif d9owtLsUm1L8qQbnI2hIqhXvptzrbRX9ttXd0KaTReLI3qaMpmAg3Uhg//C06ubyhEzC 6Sp3STE7JwT5tv9y43Rrg2EgrYHhkTQ5xYHlcl8iTw2K9NjGsI+jpir5ZU5m2r/ypIFV ekaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752572051; x=1753176851; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=HKm1OPddzPOCVybWQJf7fIOws1hHLUPbnC0KechHFr4=; b=S8jSuBd1ne90UPFMtnwmF63xVesD7pLS4k9qoWxj6OUp0g33P644k0Vnhn3P/e2W3z he15bC9t0EGWAYwPiJq9DdJ4fELqJDuhdrdixiV7sCQcgkfZrTT7ySmvdh41gk3Oj6Qe kl7kVyBS6ysiM2l4eCxde9l1VvxrKCONuDMmJEzooYDP55gOX3mPGU7QwMiy7PyouiF1 fTTamCGrb3LgqHfrqX6bkz3W6QjqB+CD47gfXP/Rt1s4wGRX9HNJBFng4uy+YZ4bLdRy XA6i2RTxdTL/ONJiHbXNNl85INziHyETSmwlP0sPGI+/oRZFeECLbq/MX/OMUBXapSzc Jt+A== X-Gm-Message-State: AOJu0Yzrznm2dg42O2MZpxWf2WdegBgJFpoe1YblUmb49vpW9CaDBZ7n UQMbnNK96m5GD6Mb41f1GjNlvMIaQ3mEnLNknXWIn+huOo8LeFrQkrWMswCeb8MaWIOmLdU9ymh beMMYmprlW+uU4Az4yzT5FEjKDx4MG0fEW+m/rh3k7BssWaBQv9lPIgIK/Usmo7EiL4pmI2P9AW t44X9b/Ltf4m1JYvRTSfXEvE2BtLs= X-Google-Smtp-Source: AGHT+IFb2OSH7lEKwhbKN8+t42ZlOCnkfwV4bEknRLarq2YT9adSgiVMvCqHjEbxvfjY3zoBqSDXrJRWaQ== X-Received: from wrpf9.prod.google.com ([2002:adf:f449:0:b0:3b2:5edb:a37b]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:2086:b0:3a5:67d5:a400 with SMTP id ffacd0b85a97d-3b5f18b3eaemr14590340f8f.33.1752572050760; Tue, 15 Jul 2025 02:34:10 -0700 (PDT) Date: Tue, 15 Jul 2025 10:33:38 +0100 In-Reply-To: <20250715093350.2584932-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250715093350.2584932-1-tabba@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250715093350.2584932-10-tabba@google.com> Subject: [PATCH v14 09/21] KVM: guest_memfd: Track guest_memfd mmap support in memslot From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com, tabba@google.com Content-Type: text/plain; charset="UTF-8" Add a new internal flag, KVM_MEMSLOT_GMEM_ONLY, to the top half of memslot->flags. This flag tracks when a guest_memfd-backed memory slot supports host userspace mmap operations. It's strictly for KVM's internal use. This optimization avoids repeatedly checking the underlying guest_memfd file for mmap support, which would otherwise require taking and releasing a reference on the file for each check. By caching this information directly in the memslot, we reduce overhead and simplify the logic involved in handling guest_memfd-backed pages for host mappings. Reviewed-by: Gavin Shan Reviewed-by: Shivank Garg Acked-by: David Hildenbrand Suggested-by: David Hildenbrand Signed-off-by: Fuad Tabba --- include/linux/kvm_host.h | 11 ++++++++++- virt/kvm/guest_memfd.c | 2 ++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 9ac21985f3b5..d2218ec57ceb 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -54,7 +54,8 @@ * used in kvm, other bits are visible for userspace which are defined in * include/uapi/linux/kvm.h. */ -#define KVM_MEMSLOT_INVALID (1UL << 16) +#define KVM_MEMSLOT_INVALID (1UL << 16) +#define KVM_MEMSLOT_GMEM_ONLY (1UL << 17) /* * Bit 63 of the memslot generation number is an "update in-progress flag", @@ -2536,6 +2537,14 @@ static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu, vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_PRIVATE; } +static inline bool kvm_memslot_is_gmem_only(const struct kvm_memory_slot *slot) +{ + if (!IS_ENABLED(CONFIG_KVM_GMEM_SUPPORTS_MMAP)) + return false; + + return slot->flags & KVM_MEMSLOT_GMEM_ONLY; +} + #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn) { diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 07a4b165471d..2b00f8796a15 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -592,6 +592,8 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, */ WRITE_ONCE(slot->gmem.file, file); slot->gmem.pgoff = start; + if (kvm_gmem_supports_mmap(inode)) + slot->flags |= KVM_MEMSLOT_GMEM_ONLY; xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); filemap_invalidate_unlock(inode->i_mapping); -- 2.50.0.727.gbf7dc18ff4-goog