From nobody Tue Feb 10 06:06:14 2026 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (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 85AC72575B for ; Thu, 22 Feb 2024 19:06:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708628793; cv=none; b=IQ7vuKymfPVrkZIpObS7yINzrjjdDnaEAByuNo/26nF0wnqTTvfC1+zE8qY/MwRrVSxoCaX9oeZipI6O5Mwz4fw0dLCfwt1Wd+yNxKAKAqzhfH8C74GyQlEBipDp/6JAiFRfEq5NK9n/EcfB1tYQBqKATX7em3kNnDhNN2gWXZU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708628793; c=relaxed/simple; bh=nieUYnH4dj1j92uddbXN4kJMJyMCVisTdazPsZdBPn8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=VpzpsMllXL3mXuabaFSP6z5X26tZNcIbwBcf2Z/VdiOuSlqY8YCFhLdKl1g5wYiFmF3e99LonCBH1ZDsb4FvJnG+HOK5BDK1Xeyh+braEKsYdbRFUh6+cr4E+pXuuEeeXPsfyhP5E2T/MgezL7gyflr4IHsZp/Iv9JrRmB0pS6A= 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=K+Kfykx9; arc=none smtp.client-ip=209.85.128.202 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--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="K+Kfykx9" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-6085e433063so1143317b3.1 for ; Thu, 22 Feb 2024 11:06:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1708628777; x=1709233577; 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=3ntMGhr684dTjFjW5K9N11e4M8SUGzq3A8ac/2w/QBo=; b=K+Kfykx9Hq+ykAkYNd4G4I85Sjt9YcnQ4siJNsHr2te3tcKrZdZllffe8rBFSIkLGd BDQ/C1Ay+W8/Tz91cWU6OofJ1tfDPEY5XDXXst0d/jsBYrT65Pnp5H+z4bYxI2aoaFD5 w7d8Dcz7zTbdxZMQs5bzoVTeLyRO0dqIlL1ZsKo86ueEB9bDD2E3QFR9mlte87HADtBt aKzT1cX3xQN80xT53oxMNGPaDp2KDzNKfovzwIxbz9JKm1iNQfgK5GroprazRUXK2S8j VqBeCRPvPa2jRrfFbvA7+bW1R8O8qSUF77rm24zvjQRIwodF8TFWc0vaBXMzLoARdZ5U RNnA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708628777; x=1709233577; 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=3ntMGhr684dTjFjW5K9N11e4M8SUGzq3A8ac/2w/QBo=; b=Erp4FM6I2j25mWuWkQzsp5k/6K2JK7O6eYak+QXaiKI3fHTYI61LBp/7qwxL4DkG7U W79sLXLSn5S/cBYJSwuzk5U22WubeurA1u4TvXMiKt2fRJMLconLeqv87agNZCfjxcH9 hZ3z13IaqLU9Y18G9bxkIwM36vfigTDxYplik5o61/snJ4iVT0LA2RZBa5yhROqlbtIT m86qE2v+gsiXhuZwRHVhjH5u5VGUDUtuqbz35+/Uc788nL4j22I9keoAM+1tBQPH9QcO y9SV0rm3P6USH/Yd3L07I27QfQrZQ4YF+znlRJ4sXKmTxmV/8bPYzIo9LjT3iS9wImGE OAbQ== X-Forwarded-Encrypted: i=1; AJvYcCWa+CsObYUvdhQ//WeBsWBOz5EbDx/2UiMTw2v/kvaEUrLryWpllGa4bNpJ3SX93z8Fov1ynyzujZ4pw0vFYK6wsrHFVFW9F61vi5e6 X-Gm-Message-State: AOJu0Yy9r5KOego5Thopr5kt6qeJ6rmvTDINgdHqanwORF0W+OjjU/bE p+Zg9qz1MjIRvE9r7vh2aqWPp13kYAzDP9YZkIfauARwTFpqFsDIC72RH17AgMKefHhmZtqLM2+ Ofw== X-Google-Smtp-Source: AGHT+IGJTwZNTDdlTJ5vrQNg9sqTJ09fKYXStOw2msJafDEAYLjbX78aWrh79pmG9gxDUQhCFn+wShlhb8g= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:160b:0:b0:dc7:7ce9:fb4d with SMTP id 11-20020a25160b000000b00dc77ce9fb4dmr5036ybw.12.1708628776828; Thu, 22 Feb 2024 11:06:16 -0800 (PST) Reply-To: Sean Christopherson Date: Thu, 22 Feb 2024 11:06:08 -0800 In-Reply-To: <20240222190612.2942589-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240222190612.2942589-1-seanjc@google.com> X-Mailer: git-send-email 2.44.0.rc0.258.g7320e95886-goog Message-ID: <20240222190612.2942589-2-seanjc@google.com> Subject: [PATCH 1/5] KVM: Make KVM_MEM_GUEST_MEMFD mutually exclusive with KVM_MEM_READONLY From: Sean Christopherson To: Paolo Bonzini , Sean Christopherson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Fuad Tabba , Michael Roth , Isaku Yamahata , Yu Zhang , Chao Peng Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Disallow creating read-only memslots that support GUEST_MEMFD, as GUEST_MEMFD is fundamentally incompatible with KVM's semantics for read-only memslots. Read-only memslots allow the userspace VMM to emulate option ROMs by filling the backing memory with readable, executable code and data, while triggering emulated MMIO on writes. GUEST_MEMFD doesn't currently support writes from userspace and KVM doesn't support emulated MMIO on private accesses, i.e. the guest can only ever read zeros, and writes will always be treated as errors. Cc: Fuad Tabba Cc: Michael Roth Cc: Isaku Yamahata Cc: Yu Zhang Cc: Chao Peng Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-spe= cific backing memory") Signed-off-by: Sean Christopherson --- virt/kvm/kvm_main.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index eb0dfcd157f4..0f9f78f4f7cf 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1617,7 +1617,13 @@ static int check_memory_region_flags(struct kvm *kvm, valid_flags &=3D ~KVM_MEM_LOG_DIRTY_PAGES; =20 #ifdef CONFIG_HAVE_KVM_READONLY_MEM - valid_flags |=3D KVM_MEM_READONLY; + /* + * GUEST_MEMFD is incompatible with read-only memslots, as writes to + * read-only memslots have emulated MMIO, not page fault, semantics, + * and KVM doesn't allow emulated MMIO for private memory. + */ + if (!(mem->flags & KVM_MEM_GUEST_MEMFD)) + valid_flags |=3D KVM_MEM_READONLY; #endif =20 if (mem->flags & ~valid_flags) --=20 2.44.0.rc0.258.g7320e95886-goog