From nobody Wed Dec 17 10:45:04 2025 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (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 1570B17B41F for ; Fri, 12 Jul 2024 17:01:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720803683; cv=none; b=OaHE14K+uIUcVvdcwu7PErLTLwtupr1JW6BukfzrfJ7IskHT6+J43X9I8HOiB5p4hu47b2m4gWRjTNA5jSOo6RajB5ZnutU9+aPWahMlx3P40/14NFXaYXUbl+wQ6am64hbYxvO/I3U7k3dJiUUEaDdovwprAHFOwrdaTNdZqqE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720803683; c=relaxed/simple; bh=JV+LctEmZ8RVScnNvPDQmSmCQdrPRydUorU75kWraZk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=p9wXEem6RUzMsTgdvPtf3jaUrm/+tCjy3tkE8t743AFAqnrepWsL/xE7ak4rRAWRLKbzpj9VNd1f+BfSHJ4Tvs2jO/kHa1XjbXMR0oAKyc06fEFR7o7a1Ji6PR37OymWsO24hZSGuWIMJQKe2URQFYF8xeCsiqKeNF0ZRdz00qE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=FZbsFT+f; arc=none smtp.client-ip=209.85.128.73 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--jackmanb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="FZbsFT+f" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-426703ac975so12905095e9.0 for ; Fri, 12 Jul 2024 10:01:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1720803680; x=1721408480; 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=jms+qnUoGWR3Ok8D5PSRh1HvZeNFLLNfdQwhqdA9AN8=; b=FZbsFT+fMDAuUgio48QK61G8Yxlx/8W5pbGp04kifviTcGbOfXubWv+6lPj7XuuRIm JoGdvNbW7IXh54dcdDR+0Gx8G0PABCk6RdhxkKcKyNzcLq2s+baZ67N6sT0u07UaefZt i8A//X66F5F9HiH7RkFxhKM4y3gnO8h99dP5blKtBPczwkXB2gd9BvgY7x955J44ueCF nz/W+DYg3rXxwQAvJPPCdh3QEIefThWUbVRRRJr7fN5vwjmNG5+9ayeZPc08Tc4i/tr6 /+Q8LnNcd9K7msMIe1kBVfg9P/U3Lg6zC00FNdq9vuRHaAGGhvnuedXt8QX29oWTTNB5 Cz+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720803680; x=1721408480; 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=jms+qnUoGWR3Ok8D5PSRh1HvZeNFLLNfdQwhqdA9AN8=; b=r1SnNLoO/CC8B6K7wp3whVzkd6vHxPHNpvHkfv2OfJg/LyrL7Rp2QLfFsv35PW6CG4 bzmz4W3Q339FpdvGpucsZiElLnJ1ZdhZWOyX4JMg5Hi/qPkIvEBX4TbtSA+3MWD0Iic9 O/fGiWa5HLt559vqUjkTTF5z9vLu7MH9/i+zyj2naOHedK3OFA1BH72HpM7SEKWgPMQ2 nGxe6wy8S22KcCZUJpKrHmpNHJ6l/d5owbAwwE4pNg1tTcvLg+ik5Ycfg6O0PDcWCtDp QqFaOs2uXMOiOHdXB1DdGkSPQ8GUZAZZy4bnotCf/5AwyEawWIyQo5fHIPhGwz/R3DSz p1xQ== X-Forwarded-Encrypted: i=1; AJvYcCXlRd4LFnkZraenI2QdUMSENg0HOfTTM98hoqVXvJImlcPLg7m6V0dnhZdgyZ+Zv+2+CGiBHHXmRwiKI4Li1eLNB+HbL/nW7eAZgVXd X-Gm-Message-State: AOJu0YwIUKAeJtt6EDKaj+Vq1uSYTqh4DZC3bX5YnQ5iloyyJx+Fh6Lc l0aLPSY4JEBqMkz/y77tXFcXEe8fZclNY/Ms+41Q1QHoMMl//D3zNTmimkPQ4Q0URRAOnCS3fjb of18qzWx5oA== X-Google-Smtp-Source: AGHT+IGisRm/zH5xPuc3vZntkMct9zRaY/l9dILlFDVOJcrKy+wGrjnqUwhX4l9eAthBD2p9mDlo+nx2x2+a6A== X-Received: from beeg.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:11db]) (user=jackmanb job=sendgmr) by 2002:a7b:cb11:0:b0:426:670b:20bf with SMTP id 5b1f17b1804b1-427a0a24cb6mr168765e9.0.1720803680269; Fri, 12 Jul 2024 10:01:20 -0700 (PDT) Date: Fri, 12 Jul 2024 17:00:28 +0000 In-Reply-To: <20240712-asi-rfc-24-v1-0-144b319a40d8@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240712-asi-rfc-24-v1-0-144b319a40d8@google.com> X-Mailer: b4 0.14-dev Message-ID: <20240712-asi-rfc-24-v1-10-144b319a40d8@google.com> Subject: [PATCH 10/26] mm: asi: Avoid warning from NMI userspace accesses in ASI context From: Brendan Jackman To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , Paolo Bonzini , Alexandre Chartre , Liran Alon , Jan Setje-Eilers , Catalin Marinas , Will Deacon , Mark Rutland , Andrew Morton , Mel Gorman , Lorenzo Stoakes , David Hildenbrand , Vlastimil Babka , Michal Hocko , Khalid Aziz , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Valentin Schneider , Paul Turner , Reiji Watanabe , Junaid Shahid , Ofir Weisse , Yosry Ahmed , Patrick Bellasi , KP Singh , Alexandra Sandulescu , Matteo Rizzo , Jann Horn Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, Brendan Jackman Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable nmi_uaccess_okay() emits a warning if current CR3 !=3D mm->pgd. Limit the warning to only when ASI is not active. Co-developed-by: Junaid Shahid Signed-off-by: Brendan Jackman --- arch/x86/mm/tlb.c | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 02f73a71d4ea..e80cd67a5239 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -1326,6 +1326,24 @@ void arch_tlbbatch_flush(struct arch_tlbflush_unmap_= batch *batch) put_cpu(); } =20 +static inline bool cr3_matches_current_mm(void) +{ + struct asi *asi =3D asi_get_current(); + pgd_t *cr3_pgd; + + /* + * Prevent read_cr3_pa -> [NMI, asi_exit] -> asi_get_current, + * otherwise we might find CR3 pointing to the ASI PGD but not + * find a current ASI domain. + */ + barrier(); + cr3_pgd =3D __va(read_cr3_pa()); + + if (cr3_pgd =3D=3D current->mm->pgd) + return true; + return asi && (cr3_pgd =3D=3D asi_pgd(asi)); +} + /* * Blindly accessing user memory from NMI context can be dangerous * if we're in the middle of switching the current user task or @@ -1341,10 +1359,10 @@ bool nmi_uaccess_okay(void) VM_WARN_ON_ONCE(!loaded_mm); =20 /* - * The condition we want to check is - * current_mm->pgd =3D=3D __va(read_cr3_pa()). This may be slow, though, - * if we're running in a VM with shadow paging, and nmi_uaccess_okay() - * is supposed to be reasonably fast. + * The condition we want to check that CR3 points to either + * current_mm->pgd or an appropriate ASI PGD. Reading CR3 may be slow, + * though, if we're running in a VM with shadow paging, and + * nmi_uaccess_okay() is supposed to be reasonably fast. * * Instead, we check the almost equivalent but somewhat conservative * condition below, and we rely on the fact that switch_mm_irqs_off() @@ -1353,7 +1371,7 @@ bool nmi_uaccess_okay(void) if (loaded_mm !=3D current_mm) return false; =20 - VM_WARN_ON_ONCE(current_mm->pgd !=3D __va(read_cr3_pa())); + VM_WARN_ON_ONCE(!cr3_matches_current_mm()); =20 return true; } --=20 2.45.2.993.g49e7a77208-goog