From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 AB05B13F018 for ; Fri, 23 Feb 2024 17:36:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708709820; cv=none; b=adtwFLQ80PXhHxmz2jE5F71+b7ps8YmjbzGHdkE+FV63cH+8JMw+qZpBB2Q9OHrCi3FNZiyzaRba+Cmy30UDRGRJ+JGJmw8bO0CKy/zXCaqCdI1fxu3u1K4ob5CB2PTvCPQ+tz2KFLt8ZJGnMTJhln/MdOBYPlE1w1IbdRxdpAc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708709820; c=relaxed/simple; bh=mPq99SHVDAlyu/Lw6k/HCBY8a5P8RgeYGBIuIYVU8jU=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=VzduhiXoJZ5eCAlJ/KuqFbYlDeZfLBrtBtfRq7VvYmTaoKBv8TKm9QzwE4noUaIHuHw20Q2CU1VlJlWei1ybYhy0EUSANnck18o+AqSFh6J61Df/bRX/rtIcRN9/2GSdtSBEyNCatlGmgx4FmNn2u6QLTJVSiQ+XOnYfjG7WJO4= 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=vZVfto5x; arc=none smtp.client-ip=209.85.219.202 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="vZVfto5x" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dcc4563611cso1824642276.3 for ; Fri, 23 Feb 2024 09:36:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1708709818; x=1709314618; 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=vQFkD/yeaXafYTambjNc8nGAaM5dCANMqU9RXbu0aLA=; b=vZVfto5xhOFCLp49Hgi85KvUoY/pi52vzZf5i2PPR+Mx1mzavSmBIjMWZdobDQv7jc uQR3zDF6XXOgf0E/Bza0yv57kNq+IlARkyHSl1ibhABzpULF74xsSs3/8jnxVI61YT7m jyjPkAR31z9lNJGcDKClUEAzamfKXHOUSE3N8XJxcUonKxXkacg8Ucjrlk9U1qopaM8V SGrFG4kDrYIgFD86g8bhTFHrJoS0UE5ZjrxXHHCyBC/JgBEnWA9EgvdtKaFpnqsSliP3 b5jpUbsMNDeIEvkxwRMQSBPkWC33urPVQBcV7gkzGaykj0+5tJISmH+Vwvj65BoepVr5 mx+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708709818; x=1709314618; 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=vQFkD/yeaXafYTambjNc8nGAaM5dCANMqU9RXbu0aLA=; b=rTHBgsnOlcRZpPtnph1UFwQEfb/mMqjIE+89r3VpbSmrHpK8evjsOd66900rAeVtqw qcHk/fKhWy7k0bPMssqTuEfIzDxuPeJqtbZdFlPvbwqcSYO8983XUe+4FxPdP9QFot8W XiDEZOr3lwnO7qIzu6wEazFFWZm+QECMf1AlGEHu57b9gj/Eu9IZslHrRrJmCinr4Z5y J13tagTqETnsgenx7Y7UoY5HDcZ610HeZ7chh8XFf0gPjrQimg7fLpAnrzM6Iv85jzCN MBD6/LJkoa0Fxk5cZMXSCADxicV0TGRCyvdiUvzyqCB10jCLgEMBeeGAXnQDBcnNdDYj ITDQ== X-Forwarded-Encrypted: i=1; AJvYcCUvbPeqT3AXCnv2irhesqSMesaV9Ui2ULKoBdVLGTnNNaRXDMa5hlVroIblY+D9F5CIGMj4lyC6IUQbYB+x3ECXo/xCT8fDMHjRrrP3 X-Gm-Message-State: AOJu0Yz/NG/L75FGFN3LJgsLdZcBCk5oZGRckvE+smTA9HBVZ7L1Q2/A W5WDh5d8oZPXWJDvSPdWOef4xtywYpr3Cp51qKUtamkw98TOUpy5yHLDsvsbXxZiD4BJPYlkQts 7lA== X-Google-Smtp-Source: AGHT+IF6qHLLb++rm38SnHHY1oMkxzeH9qs55zcOOM7YnS3PnobaoRSUe6xFvYZWf184A1ED5DElZhno5QQ= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:ad9a:0:b0:dc2:550b:a4f4 with SMTP id z26-20020a25ad9a000000b00dc2550ba4f4mr124968ybi.1.1708709817812; Fri, 23 Feb 2024 09:36:57 -0800 (PST) Date: Fri, 23 Feb 2024 09:36:56 -0800 In-Reply-To: <20240221072528.2702048-10-stevensd@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240221072528.2702048-1-stevensd@google.com> <20240221072528.2702048-10-stevensd@google.com> Message-ID: Subject: Re: [PATCH v10 7/8] KVM: x86/mmu: Track if sptes refer to refcounted pages From: Sean Christopherson To: David Stevens Cc: Yu Zhang , Isaku Yamahata , Zhi Wang , Maxim Levitsky , kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Wed, Feb 21, 2024, David Stevens wrote: > + * Extra bits are only available for TDP SPTEs, since bits 62:52 are reserved > + * for PAE paging, including NPT PAE. When a tracking bit isn't available, we > + * will reject mapping non-refcounted struct pages. > + */ > +static inline bool spte_has_refcount_bit(void) > +{ > + return tdp_enabled && IS_ENABLED(CONFIG_X86_64); > +} > + > +static inline bool is_refcounted_page_spte(u64 spte) > +{ > + return !spte_has_refcount_bit() || (spte & SPTE_MMU_PAGE_REFCOUNTED); The preferred way to handle this in KVM's MMU is to use a global variable, e.g. extern u64 __read_mostly shadow_refcounted_mask; that avoids conditional branches when creating SPTEs, and arguably yields slightly more readable code, e.g. return !shadow_refcounted_mask || (spte & shadow_refcounted_mask);