From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (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 709EA15B99E for ; Mon, 19 Aug 2024 22:47:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724107640; cv=none; b=HmIXv+FS4E1YyNjNp6jBEUaddKp0NAq5zesT/A5CVdQlqfXGYfM6zmsgfcMQNSTT9ESVE47JB7iU8eVl7ZUsp4WuPhTkDK2yCpThux3/SUIjzXubtKqqJtDYCIl0Ainr6wwfOsVAB7+kXFRehdSKPYBkDPjXiGxJoGIPnvs9+wU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724107640; c=relaxed/simple; bh=VDHlprhqwjCM5N4nwmrW+/M8UE6X+2dcwSHCzgZZckE=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=G6Y3/spf+MDM4RWbGsLlIyVCdJXIu3wsDxPRD1+jN4qBdnroshRqIM2jIYx8B6jh0mPEe0JoO330IplIcaGiVa5Fx7Rj8YL7y0jA+bGbPRCSruErL3XWK6w39XGVp45c4UfG0/fnzTEIKCpMNNTHBmNmjbx8kbqHEfVLTeemnM8= 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=GRib77bB; arc=none smtp.client-ip=209.85.215.202 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="GRib77bB" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-7163489149fso4406512a12.3 for ; Mon, 19 Aug 2024 15:47:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1724107639; x=1724712439; 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=0mpr7864OCZvv9Hj0Yv++YX+VmARQzYZRUR5rU9bOeY=; b=GRib77bBvuS54zVEHsxcUHiR1ATqHPtnZ0xESmawQTlLv1Ib7SqbQkkMxRunQmPA0B W0GHItnH3tz5SofclG0kBJoNYYXCplWh/PTDaIarpYxUsoRdoymc/5a62C50UifSmjJ8 OCevUGwGgv5nLbYihzWy2PftYtd8bx8cuEnOV7+649T3sS1DhEst/f+DLD43dHN8NpSD OEBzZQHc8Y1QIx57Yjo+HmMWLNEu1XBp8lBJOUduEOpDShDWf0edME8PdxO/iG62CmEr OvdYeU3PHgvDD8iYgxuGlBnXUFrIvX13G/+HFdT/cIenuchJWXa6Gi/BbRIIwxsvg/Ls WxoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1724107639; x=1724712439; 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=0mpr7864OCZvv9Hj0Yv++YX+VmARQzYZRUR5rU9bOeY=; b=mYj8mKxwh0gltPI44TjqSg2vhIFQ8zkiKHBytC09NW7kpVZUmcKuip1bIZm1zIZ+/l qoZgZ72VBhrlVl1Fhe4eSGKnRuJbk4CjLbVN1Pb6X9A2SahcC8pdTBxpvABtRVnevzqz CCKjnDjLFwqQIpPWR0H30dDqKmvZBOycv29I43evv2bw05VkBKF3mjSd+8ib5mCcS4Ea LWjasV/8DNznoVuLG1MgRq+KCpIbXv5BIoh+96p/XiLLFwfpKqRxt+sQxW37XPl7GHem U5OfrdWuVhQgszEFJycK1sVjCCw17ueAoKdUHZSlY2xcTAhfcsdxtTlCG7VitHRZho+J 6/ew== X-Forwarded-Encrypted: i=1; AJvYcCUhBBd30U8ya0UAlz9nxHafQgtnB7LmVzp/0Jb2V7mMGwUTC6tg1b0b1/FlFWSn+zSo9UI=@vger.kernel.org X-Gm-Message-State: AOJu0YzBI8pFZ5kvvrQFG9qEPIZhjMobsYU9Wn9fRDZcooWndqpDGCOc Ct3+vhYLFL7bKCx+u+fCOP9uCR8fGWBmCTNmvdzKgVDuhBuPv0pSDweZ9DYsMoZbhS+cZ34i16a 9gw== X-Google-Smtp-Source: AGHT+IGngB58TyyXwtykQy2TchYmizV3K6F19AJubcP5aFPXxhvBteRSy0IDpLShOfEeLOPTdkLjdiTkkuE= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:903:247:b0:1fd:8e8d:8695 with SMTP id d9443c01a7336-20203f27f39mr13121725ad.12.1724107638639; Mon, 19 Aug 2024 15:47:18 -0700 (PDT) Date: Mon, 19 Aug 2024 15:47:17 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240724011037.3671523-1-jthoughton@google.com> <20240724011037.3671523-4-jthoughton@google.com> Message-ID: Subject: Re: [PATCH v6 03/11] KVM: arm64: Relax locking for kvm_test_age_gfn and kvm_age_gfn From: Sean Christopherson To: Oliver Upton Cc: Yu Zhao , James Houghton , Andrew Morton , Paolo Bonzini , Ankit Agrawal , Axel Rasmussen , Catalin Marinas , David Matlack , David Rientjes , James Morse , Jason Gunthorpe , Jonathan Corbet , Marc Zyngier , Raghavendra Rao Ananta , Ryan Roberts , Shaoqin Huang , Suzuki K Poulose , Wei Xu , Will Deacon , Zenghui Yu , kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Mon, Aug 19, 2024, Oliver Upton wrote: > On Fri, Aug 16, 2024 at 07:03:27PM -0600, Yu Zhao wrote: > > On Fri, Aug 16, 2024 at 6:46=E2=80=AFPM Sean Christopherson wrote: >=20 > [...] >=20 > > > Were you expecting vCPU runtime to improve (more)? If so, lack of mo= vement could > > > be due to KVM arm64 taking mmap_lock for read when handling faults: > > > > > > https://lore.kernel.org/all/Zr0ZbPQHVNzmvwa6@google.com > >=20 > > For the above test, I don't think it's mmap_lock >=20 > Yeah, I don't think this is related to the mmap_lock. >=20 > James is likely using hardware that has FEAT_HAFDBS, so vCPUs won't > fault for an Access flag update. Huh, didn't know that was a thing on ARM. Ooh, that lends even more creden= ce to my assertion that marking folios accessed in handle_access_fault() can go a= way[*]. I assume hardware-assisted updates means this code in handle_access_fault()= will no longer be hit, as KVM simply won't ever get access faults? If so, I'll = add that info to the changelog. if (kvm_pte_valid(pte)) kvm_set_pfn_accessed(kvm_pte_to_pfn(pte)); [*] https://lore.kernel.org/all/20240726235234.228822-83-seanjc@google.com > Even if he's on a machine w/o it, Access flag faults are handled outside = the > mmap_lock. Oh, right, they go down handle_access_fault(), not user_mem_abort(). Reviewing late Friday afternoon, never a good idea ;-)