From mboxrd@z Thu Jan 1 00:00:00 1970 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 92CD914F9C4 for ; Wed, 31 Jul 2024 20:36:27 +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=1722458189; cv=none; b=LlHkVWjH6Y23WM00l9zt0wE2EibeEF1RLP1jMkOpqqMQpIcj/9iU7cPVhgfjSbBK6Qt8EyY/FOaUq/3+yaW5riccKeWz0YrSCu5BgS08X3+4jD7h/SzhIlxNZGpduSz4mmqLOHJK1Ct6qyxMFZ1KZR+mrb6DNRUcBdlfP59k5Jw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722458189; c=relaxed/simple; bh=z1aLVeNoBym3Qjn/r9ThqGkDG4AOjTwKh0lTuQS/B+0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=gkj/4Res8kV9+mxm2wSw1qV4uMG41ANRZXNErHgkrIo/kyGqyeUkSYOGCYbfYF3XNs3NiF8T08lRWcDFsvazg7c+PDuf7Fv+R11dj0RdzTWgfezx7t4DeBBes1NbdHQAhZvVruaHDbc02PNpENN5jZuLthIergDvj9r2NC1YS/4= 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=WeyhuXd7; 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="WeyhuXd7" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-664aa55c690so124095567b3.2 for ; Wed, 31 Jul 2024 13:36:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1722458186; x=1723062986; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=Kd/mYHbPzOSIwsUM5m5UMPqJkKyWoklOLcVSOqbILGs=; b=WeyhuXd7I/9HsccEAdIat5gekMhyyetArz33y71PyOc1qGoQJ6ZwTwBU03VoYXUnjD nleVvSHuWKdvCA3G7jTW+JyMb9C8y1Cqbm6qVrQshdRN5ZLI/gBd6RMO81liQzZstVYW bfIMboSjdr0bh9YSPItGecdUGm+i01vFy5gNWEn0w0xs4c+z9FTe19ekN+/YwDyMTYrr dIa7LEg8wKXE3iDFHkisRRFDSpV74+q8hahraJeruURji5PC1E9eVja5XUcycN+yD+MK 6OT5iaX53wAvq9jSvmzfrAAdqXPgADCq50O7SFCAyFR+mpH8ndIPYZuW9/woaDSIR6N7 HblA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722458186; x=1723062986; h=content-transfer-encoding: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=Kd/mYHbPzOSIwsUM5m5UMPqJkKyWoklOLcVSOqbILGs=; b=A1gPCZXSId78bOV7qdsN4Z3K4LNinYeNxPW5PoLJNnXeF0n8ibFqrifQLiZoaDjtTk nxKj2lNkKGJv52bEUBb3vMLk7vDsh/coPVOp3yg+lCVIt8DEIpNXpypkO5gap9B3WjR+ fZppj0Fb/V1WI/Vhgn6qH97wL4Pikx+2tw31pjFWlwQvrfthULJpQ99U9RdhK7wesyjB c0ZgrnukJ3mLqq22JFmPWUTwNkOBzZQ6yCoSrjE7mXOExjqbMX2cjlp+HItNi/vt5U/X ik6qIJpZf30WdWeZjgX/SgXSeGWeOR1VDWVVbvmVxhqz3lE0OTm4nadrq96PbMj+3lFS JxHw== X-Forwarded-Encrypted: i=1; AJvYcCVSG5PcSDUK9YuQUb78rUHqraxjLE8Shu2hQ5FxdVULjOKsoFWK8YUB9elWQY95J4d9EJvxVxJlz6DzU8yNhpm81+zVUDhYpXfYqw== X-Gm-Message-State: AOJu0YxO9B+J8u8DsrDn293wI0TV2lUVQgXaYx/66N9A4mPdNwne9BIn yoOsQaNmJAOPZ2qM3qiUZ10j7FGWpwIFzKqlQq9oGK/HlXrssqaxdbqyl5nSXqzjWQESO7Ajq7h 2mA== X-Google-Smtp-Source: AGHT+IH0DRpeCdEjd5+EVXte2iiNPB7q7dTvECq86U0Z8nMo4fguKYduL9RXt42ZsXAM2SH8mq6gA4JZJ0k= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:18d2:b0:e0b:bf20:4ff8 with SMTP id 3f1490d57ef6-e0bccf7b434mr932276.0.1722458186501; Wed, 31 Jul 2024 13:36:26 -0700 (PDT) Date: Wed, 31 Jul 2024 13:36:25 -0700 In-Reply-To: <87a5hxfs3d.fsf@draig.linaro.org> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240726235234.228822-1-seanjc@google.com> <20240726235234.228822-2-seanjc@google.com> <87a5hxfs3d.fsf@draig.linaro.org> Message-ID: Subject: Re: [PATCH v12 01/84] KVM: arm64: Release pfn, i.e. put page, if copying MTE tags hits ZONE_DEVICE From: Sean Christopherson To: "Alex =?utf-8?Q?Benn=C3=A9e?=" Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , David Stevens Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Wed, Jul 31, 2024, Alex Benn=C3=A9e wrote: > Sean Christopherson writes: >=20 > > Put the page reference acquired by gfn_to_pfn_prot() if > > kvm_vm_ioctl_mte_copy_tags() runs into ZONE_DEVICE memory. KVM's less- > > than-stellar heuristics for dealing with pfn-mapped memory means that K= VM > > can get a page reference to ZONE_DEVICE memory. > > > > Fixes: f0376edb1ddc ("KVM: arm64: Add ioctl to fetch/store tags in a gu= est") > > Signed-off-by: Sean Christopherson > > --- > > arch/arm64/kvm/guest.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c > > index 11098eb7eb44..e1f0ff08836a 100644 > > --- a/arch/arm64/kvm/guest.c > > +++ b/arch/arm64/kvm/guest.c > > @@ -1059,6 +1059,7 @@ int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm, > > page =3D pfn_to_online_page(pfn); > > if (!page) { > > /* Reject ZONE_DEVICE memory */ > > + kvm_release_pfn_clean(pfn); >=20 > I guess this gets renamed later in the series. >=20 > However my main comment is does lack of page always mean a ZONE_DEVICE? Nope. > Looking at pfn_to_online_page() I see a bunch of other checks first. Why > isn't it that functions responsibility to clean up after itself if its > returning NULLs? pfn_to_online_page() is more strict than gfn_to_pfn_prot(). At least in th= eory, gfn_to_pfn_prot() could return a pfn that has an associated "struct page", = with a reference held to said page. But for that same pfn, pfn_to_online_page()= could return NULL, in which case KVM needs to put the reference it acquired via gfn_to_pfn_prot().