From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f202.google.com (mail-qk1-f202.google.com [209.85.222.202]) (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 7B5982010E6 for ; Thu, 9 Jan 2025 20:49:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736455799; cv=none; b=ErWbvdsXqlXvzD34wkjZV0aEbj5kaWtGIFk86ZhZPmZ2NhfnKs97RSB8WRAHZlQLRXABInRDWJZoOZ/uc5MvSoB/ogHOTo+obyi8iKFb1ayqvz+7AIzV2yUqPaxn6kCTO01flT4xDqX/bESJtopbpfIazklg701P0vI5WQ8ii2A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736455799; c=relaxed/simple; bh=6egPkffTqCljeChAEC1xtjQx5okoA3w1tTDlM9Q/gaY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=LeVPikPkXgJj8NGcaPRFzHPAowDLZ0Ebpcuct5G4cPQkWWqJ28USUhgpQw8IDPVw8Wkm4EZ6z6Q8mL0duk6XxX93ujlC0synW9BfdIf6UzH82iCy40vw2+VU4BFLNVUYNoQkQzwFGJnK86EVb/Y0AUCChzSvdU3NgqMBOno24f4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jthoughton.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=03MhANLQ; arc=none smtp.client-ip=209.85.222.202 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--jthoughton.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="03MhANLQ" Received: by mail-qk1-f202.google.com with SMTP id af79cd13be357-7b6e6cf6742so310826385a.3 for ; Thu, 09 Jan 2025 12:49:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1736455796; x=1737060596; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=4wiJ4r6U+4DKwl7a0Sm0LZeZPdZmNUbmXckiwF/fu60=; b=03MhANLQTlP0Fu/2iPumgQyVyRpCRn1PWZzRHODQNS4OCSAmwoQdzwO2/a9CJbashs utkghBzhbokcndSCNEhRS+hfIrbr3bhjIWY5AJa7mRdr8kwB0J8unrzaIstzMTgOCRMi ZAGFnPHp6Cfv+5KVR4b0mr0w6MeMIN5onDz47e8o1uFgKg7G0ErQkpviX4hYlmoZZokl iIcQdwifjCpMUrDOz+HECcf1qY0wcoWGDtpnRP7hKsdxDmgAc+CS45+sHpMm8mQTo5HH KYT2FKlxcKN9Ae2PxF3izVkPa0CHVA3T90OVKqpTA+X0HLAHrMimcFD9cCvfejZEiSZn GDyQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1736455796; x=1737060596; 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=4wiJ4r6U+4DKwl7a0Sm0LZeZPdZmNUbmXckiwF/fu60=; b=DxXfEIk7CZyJEbUc31zqe4cV94IwK/4H1h5SgJ/TJl96UzFI+GpeGCMT/PbDZtNkXd Lq6LWNrqf9DIeBmJg+kZ7WRiXt6DNSD4L3gcWSd5ScYYqwneCIQDVhSSKbDkpfvWMJ0q Ik+ZFj+v6TEuq7z9nXIiMDgySZDsIz8sdHy0tps+mx9h1oyuoP4evZtuYgZqtdD2XN6f jTNtbEb8lcLIJU1zkqAzwByPj6JigNzf4tgzr1WK8k6szbA6yPAxsrl9XxHbJgqKZv6q Kvbae0BT4M/BBWseuh4IetDVqYQRUDC08vk4yCmeMpC4nzgXEa15Irkb0J3o61M/NjAp HIkA== X-Forwarded-Encrypted: i=1; AJvYcCU8Xvy9pxg0YyojW7XkPFf6KAYysx6/vAPR67hbGIxAK7k8Oa+N5HThukSESgyPzUXpv7fJW74=@lists.linux.dev X-Gm-Message-State: AOJu0YwhLCxR0SDywFo6mFJ9WyIQe1pt0ro4+ysk+g+M8joE0Bxt0n7O NsWWLxgB/efkdrIHoAwHjJWic5937RmVRUDws5fF4WTvsBeskEW2M4mXrBmM11t17tH0psZrgtW yAskmseq/UWpKelj32g== X-Google-Smtp-Source: AGHT+IG26IPp3qbl2E13g/CbVexbYg/eWO5E84o5Ua+axOZx93ciuXt5lAWy60cQgF+PsXPiSlHQOVHo5aFaWyuK X-Received: from qkkl1.prod.google.com ([2002:a37:f501:0:b0:7b6:e209:1c29]) (user=jthoughton job=prod-delivery.src-stubby-dispatcher) by 2002:a05:620a:d87:b0:7b6:d632:37cf with SMTP id af79cd13be357-7bcd9729affmr1146945885a.3.1736455796215; Thu, 09 Jan 2025 12:49:56 -0800 (PST) Date: Thu, 9 Jan 2025 20:49:17 +0000 In-Reply-To: <20250109204929.1106563-1-jthoughton@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250109204929.1106563-1-jthoughton@google.com> X-Mailer: git-send-email 2.47.1.613.gc27f4b7a9f-goog Message-ID: <20250109204929.1106563-2-jthoughton@google.com> Subject: [PATCH v2 01/13] KVM: Add KVM_MEM_USERFAULT memslot flag and bitmap From: James Houghton To: Paolo Bonzini , Sean Christopherson Cc: Jonathan Corbet , Marc Zyngier , Oliver Upton , Yan Zhao , James Houghton , Nikita Kalyazin , Anish Moorthy , Peter Gonda , Peter Xu , David Matlack , wei.w.wang@intel.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Use one of the 14 reserved u64s in struct kvm_userspace_memory_region2 for the user to provide `userfault_bitmap`. The memslot flag indicates if KVM should be reading from the `userfault_bitmap` field from the memslot. The user is permitted to provide a bogus pointer. If the pointer cannot be read from, we will return -EFAULT (with no other information) back to the user. Signed-off-by: James Houghton --- include/linux/kvm_host.h | 14 ++++++++++++++ include/uapi/linux/kvm.h | 4 +++- virt/kvm/Kconfig | 3 +++ virt/kvm/kvm_main.c | 35 +++++++++++++++++++++++++++++++++++ 4 files changed, 55 insertions(+), 1 deletion(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 401439bb21e3..f7a3dfd5e224 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -590,6 +590,7 @@ struct kvm_memory_slot { unsigned long *dirty_bitmap; struct kvm_arch_memory_slot arch; unsigned long userspace_addr; + unsigned long __user *userfault_bitmap; u32 flags; short id; u16 as_id; @@ -724,6 +725,11 @@ static inline bool kvm_arch_has_readonly_mem(struct kvm *kvm) } #endif +static inline bool kvm_has_userfault(struct kvm *kvm) +{ + return IS_ENABLED(CONFIG_HAVE_KVM_USERFAULT); +} + struct kvm_memslots { u64 generation; atomic_long_t last_used_slot; @@ -2553,4 +2559,12 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, struct kvm_pre_fault_memory *range); #endif +int kvm_gfn_userfault(struct kvm *kvm, struct kvm_memory_slot *memslot, + gfn_t gfn); + +static inline bool kvm_memslot_userfault(struct kvm_memory_slot *memslot) +{ + return memslot->flags & KVM_MEM_USERFAULT; +} + #endif diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 343de0a51797..7ade5169d373 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -40,7 +40,8 @@ struct kvm_userspace_memory_region2 { __u64 guest_memfd_offset; __u32 guest_memfd; __u32 pad1; - __u64 pad2[14]; + __u64 userfault_bitmap; + __u64 pad2[13]; }; /* @@ -51,6 +52,7 @@ struct kvm_userspace_memory_region2 { #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0) #define KVM_MEM_READONLY (1UL << 1) #define KVM_MEM_GUEST_MEMFD (1UL << 2) +#define KVM_MEM_USERFAULT (1UL << 3) /* for KVM_IRQ_LINE */ struct kvm_irq_level { diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index 54e959e7d68f..9eb1fae238b1 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -124,3 +124,6 @@ config HAVE_KVM_ARCH_GMEM_PREPARE config HAVE_KVM_ARCH_GMEM_INVALIDATE bool depends on KVM_PRIVATE_MEM + +config HAVE_KVM_USERFAULT + bool diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index de2c11dae231..4bceae6a6401 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1541,6 +1541,9 @@ static int check_memory_region_flags(struct kvm *kvm, !(mem->flags & KVM_MEM_GUEST_MEMFD)) valid_flags |= KVM_MEM_READONLY; + if (kvm_has_userfault(kvm)) + valid_flags |= KVM_MEM_USERFAULT; + if (mem->flags & ~valid_flags) return -EINVAL; @@ -1974,6 +1977,12 @@ int __kvm_set_memory_region(struct kvm *kvm, return -EINVAL; if ((mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES) return -EINVAL; + if (mem->flags & KVM_MEM_USERFAULT && + ((mem->userfault_bitmap != untagged_addr(mem->userfault_bitmap)) || + !access_ok((void __user *)(unsigned long)mem->userfault_bitmap, + DIV_ROUND_UP(mem->memory_size >> PAGE_SHIFT, BITS_PER_LONG) + * sizeof(long)))) + return -EINVAL; slots = __kvm_memslots(kvm, as_id); @@ -2042,6 +2051,9 @@ int __kvm_set_memory_region(struct kvm *kvm, if (r) goto out; } + if (mem->flags & KVM_MEM_USERFAULT) + new->userfault_bitmap = + (unsigned long __user *)(unsigned long)mem->userfault_bitmap; r = kvm_set_memslot(kvm, old, new, change); if (r) @@ -6426,3 +6438,26 @@ void kvm_exit(void) kvm_irqfd_exit(); } EXPORT_SYMBOL_GPL(kvm_exit); + +int kvm_gfn_userfault(struct kvm *kvm, struct kvm_memory_slot *memslot, + gfn_t gfn) +{ + unsigned long bitmap_chunk = 0; + off_t offset; + + if (!kvm_memslot_userfault(memslot)) + return 0; + + if (WARN_ON_ONCE(!memslot->userfault_bitmap)) + return 0; + + offset = gfn - memslot->base_gfn; + + if (copy_from_user(&bitmap_chunk, + memslot->userfault_bitmap + offset / BITS_PER_LONG, + sizeof(bitmap_chunk))) + return -EFAULT; + + /* Set in the bitmap means that the gfn is userfault */ + return !!(bitmap_chunk & (1ul << (offset % BITS_PER_LONG))); +} -- 2.47.1.613.gc27f4b7a9f-goog