From nobody Wed Dec 17 21:14:00 2025 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 CA7FC27B330 for ; Fri, 3 Oct 2025 23:26:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759533977; cv=none; b=PKO7xLQ9kLUvzdf+E8rcYjkKK/ISIMRlIupNxPZuFDdV3RfbgGr/bP8XUSPJLijTwjhVixeZ6DnbpLYxMp/y9j/yMZbF2zoRSWBpz+kOjidD9SGnjq/ym+F/6PnsRqFJhLNls/MLFV+FZ/Vcc5l1pTOCpEOlkD7VsRsqrvbny2s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759533977; c=relaxed/simple; bh=cBSCbLGuyu0i+pnnFJtW9XyUg/AWI2CO30mF/qWuptw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=FaU1vSwzSxhABh7viB+qw+KstGB39OxOEFbHPRj43x6lSr31x0oTMMOT5YX3CnFfjgJb5ghIMM7cUhWLQZ++8fTLyH8KT7uMXM35T+orrIxFK5+TqOvy0WYsKHdrIMI+jDP7Z7gg9EThkQgdlwj5Nt/tnklz+anYLFfuNQpaBqM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=CHQYf0Tq; arc=none smtp.client-ip=209.85.214.201 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--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CHQYf0Tq" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2699ebc0319so28791565ad.3 for ; Fri, 03 Oct 2025 16:26:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1759533975; x=1760138775; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=a+1Sii0G7hC5FMVOBHLi5jl/sMVLEnhBfdq+sbGC028=; b=CHQYf0TqTZQI5I5kXp73C2fng2vjg6GDQWfALKXP3ep2AQFKRw2kyzO/NHnd3B4m09 DlOye0CDH5hs/q2W17YvzWiWhChvjdU0JCxXOxIhMKVxO9afzmribIgthk4+5P1L3wiY 7ifN7TctI6y+IfV5/25DarjHo24bi+CuGkgsG4lb7w35ZlZQf0ima8Ls0al0U1fjqVYt 2Y+kBO1Bu1PpAu3Vv4AOKLnrHe03SeSoo+TZjU5pZ0JzoYqyPQRsAEdF56q9AglFD16A s/jTJXZrpFSur5GgmNWjQxQPPmq+xKO1Ws+3RICoky7g/eMExOIxC84ydURmOZ4z2eU6 gOgw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759533975; x=1760138775; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=a+1Sii0G7hC5FMVOBHLi5jl/sMVLEnhBfdq+sbGC028=; b=mtzD661e5euJwMUxO1Oxa0/CAV9Ilk/K+9Dzd8o6JZXBehiOh+boNQ8gfCUH71SbmC ZhQWBCsEsLnjUysAe6IxPDT3j3yDXbora45p9NCnfg7PfgmMNu4HW+3ncJji6SLezPT+ unKpWpYy+USITwrQIufXHO82sV8yC3BC1JO2zWhmLOGKhpq5jnh2J/fckOL1y3w6RGFa /MrZwggm5GGoXfoETi6oaaevzfgbZWufu0hdez73KRs6/EWzCGtusePdOO+IhRihy1JB 3C4so5hEz/xK9aEM5+2yzhy1f0tItAptiUldLT+sMD5lB52HqJm6qaA0gOf4TnwztgPp 6tJw== X-Forwarded-Encrypted: i=1; AJvYcCXVtW/2EzJKl0mgeqLx59BVE48GarqV0e7Wh+mxbkk0Xa2QhquKzWvDaDRgP+DTqCSXMfUyo1wdrrnaHMs=@vger.kernel.org X-Gm-Message-State: AOJu0YwzniFqBZSs+u/bjjDq7CL81a2BENP59+BHH1zgLW6V+BlnXR/M 8DpkCA4VArDi8ZhTiREPnjwyov8lsuLGcxJXE4no+rw37QJ7gHNjhNERFe8gpYrDbYOfyXqIjas aClPeSg== X-Google-Smtp-Source: AGHT+IG79/9POvgYVBzEf8BKcEg3XVerQtIRac7iIPaoy9Au32zTuew6jnYHjJjthe8oCk/nymcslvQyqis= X-Received: from plpj14.prod.google.com ([2002:a17:903:3d8e:b0:269:7d7a:40c4]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:2c0c:b0:269:8edf:67f8 with SMTP id d9443c01a7336-28e9a6646dbmr53564545ad.52.1759533974981; Fri, 03 Oct 2025 16:26:14 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 3 Oct 2025 16:25:54 -0700 In-Reply-To: <20251003232606.4070510-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251003232606.4070510-1-seanjc@google.com> X-Mailer: git-send-email 2.51.0.618.g983fd99d29-goog Message-ID: <20251003232606.4070510-2-seanjc@google.com> Subject: [PATCH v2 01/13] KVM: Rework KVM_CAP_GUEST_MEMFD_MMAP into KVM_CAP_GUEST_MEMFD_FLAGS From: Sean Christopherson To: Paolo Bonzini , Sean Christopherson , Christian Borntraeger , Janosch Frank , Claudio Imbrenda Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, David Hildenbrand , Fuad Tabba , Ackerley Tng Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Rework the not-yet-released KVM_CAP_GUEST_MEMFD_MMAP into a more generic KVM_CAP_GUEST_MEMFD_FLAGS capability so that adding new flags doesn't require a new capability, and so that developers aren't tempted to bundle multiple flags into a single capability. Note, kvm_vm_ioctl_check_extension_generic() can only return a 32-bit value, but that limitation can be easily circumvented by adding e.g. KVM_CAP_GUEST_MEMFD_FLAGS2 in the unlikely event guest_memfd supports more than 32 flags. Signed-off-by: Sean Christopherson Reviewed-by: Ackerley Tng Reviewed-by: David Hildenbrand Tested-by: Ackerley Tng --- Documentation/virt/kvm/api.rst | 10 +++++++--- include/uapi/linux/kvm.h | 2 +- tools/testing/selftests/kvm/guest_memfd_test.c | 13 ++++++------- virt/kvm/kvm_main.c | 7 +++++-- 4 files changed, 19 insertions(+), 13 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 6ae24c5ca559..7ba92f2ced38 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6432,9 +6432,13 @@ most one mapping per page, i.e. binding multiple mem= ory regions to a single guest_memfd range is not allowed (any number of memory regions can be boun= d to a single guest_memfd file, but the bound ranges must not overlap). =20 -When the capability KVM_CAP_GUEST_MEMFD_MMAP is supported, the 'flags' fie= ld -supports GUEST_MEMFD_FLAG_MMAP. Setting this flag on guest_memfd creation -enables mmap() and faulting of guest_memfd memory to host userspace. +The capability KVM_CAP_GUEST_MEMFD_FLAGS enumerates the `flags` that can be +specified via KVM_CREATE_GUEST_MEMFD. Currently defined flags: + + =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D + GUEST_MEMFD_FLAG_MMAP Enable using mmap() on the guest_memfd file + descriptor. + =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D =20 When the KVM MMU performs a PFN lookup to service a guest fault and the ba= cking guest_memfd has the GUEST_MEMFD_FLAG_MMAP set, then the fault will always = be diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 6efa98a57ec1..b1d52d0c56ec 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -962,7 +962,7 @@ struct kvm_enable_cap { #define KVM_CAP_ARM_EL2_E2H0 241 #define KVM_CAP_RISCV_MP_STATE_RESET 242 #define KVM_CAP_ARM_CACHEABLE_PFNMAP_SUPPORTED 243 -#define KVM_CAP_GUEST_MEMFD_MMAP 244 +#define KVM_CAP_GUEST_MEMFD_FLAGS 244 =20 struct kvm_irq_routing_irqchip { __u32 irqchip; diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing= /selftests/kvm/guest_memfd_test.c index b3ca6737f304..3e58bd496104 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -262,19 +262,17 @@ static void test_guest_memfd_flags(struct kvm_vm *vm,= uint64_t valid_flags) =20 static void test_guest_memfd(unsigned long vm_type) { - uint64_t flags =3D 0; struct kvm_vm *vm; size_t total_size; size_t page_size; + uint64_t flags; int fd; =20 page_size =3D getpagesize(); total_size =3D page_size * 4; =20 vm =3D vm_create_barebones_type(vm_type); - - if (vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP)) - flags |=3D GUEST_MEMFD_FLAG_MMAP; + flags =3D vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS); =20 test_create_guest_memfd_multiple(vm); test_create_guest_memfd_invalid_sizes(vm, flags, page_size); @@ -328,13 +326,14 @@ static void test_guest_memfd_guest(void) size_t size; int fd, i; =20 - if (!kvm_has_cap(KVM_CAP_GUEST_MEMFD_MMAP)) + if (!kvm_check_cap(KVM_CAP_GUEST_MEMFD_FLAGS)) return; =20 vm =3D __vm_create_shape_with_one_vcpu(VM_SHAPE_DEFAULT, &vcpu, 1, guest_= code); =20 - TEST_ASSERT(vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_MMAP), - "Default VM type should always support guest_memfd mmap()"); + TEST_ASSERT(vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS) & GUEST_MEMFD_FLA= G_MMAP, + "Default VM type should support MMAP, supported flags =3D 0x%x", + vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS)); =20 size =3D vm->page_size; fd =3D vm_create_guest_memfd(vm, size, GUEST_MEMFD_FLAG_MMAP); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 226faeaa8e56..e3a268757621 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4928,8 +4928,11 @@ static int kvm_vm_ioctl_check_extension_generic(stru= ct kvm *kvm, long arg) #ifdef CONFIG_KVM_GUEST_MEMFD case KVM_CAP_GUEST_MEMFD: return 1; - case KVM_CAP_GUEST_MEMFD_MMAP: - return !kvm || kvm_arch_supports_gmem_mmap(kvm); + case KVM_CAP_GUEST_MEMFD_FLAGS: + if (!kvm || kvm_arch_supports_gmem_mmap(kvm)) + return GUEST_MEMFD_FLAG_MMAP; + + return 0; #endif default: break; --=20 2.51.0.618.g983fd99d29-goog