From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0023BC433EF for ; Wed, 5 Jan 2022 09:45:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239048AbiAEJp6 (ORCPT ); Wed, 5 Jan 2022 04:45:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33902 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229694AbiAEJpz (ORCPT ); Wed, 5 Jan 2022 04:45:55 -0500 Received: from mail-lj1-x22b.google.com (mail-lj1-x22b.google.com [IPv6:2a00:1450:4864:20::22b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CBD75C061761 for ; Wed, 5 Jan 2022 01:45:54 -0800 (PST) Received: by mail-lj1-x22b.google.com with SMTP id q8so49267591ljp.9 for ; Wed, 05 Jan 2022 01:45:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20210112.gappssmtp.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=m2dmWhXik/U4SGJxPR+hpy5ElrZ2heFLJksoWt01r30=; b=RJSwHhSqfttUvklQOR/LK7vkmxvpmdFAcDnTVdEWkiTcTVuOVAPkZZOW+pEERtytre DNpixvqYh4wNgFXDosGAEyD6xAsJU3P8t16gaQxtTphuyrmzjjynozwBmoTJ+jZPK3m7 g/fD+f1wXjIK2PiGvh5ulh/Ya7rKd5+iPQfMmYon8DYanQMh2CGOLwpenBaEEMTVGvrp vsXTylQeQRkcV6WwZFqrZnXXzrAGttnG1ltdjBsLtfEQeL5qfhdH0vUbfhlVDtOOAaaM LcEg/xDjLbGgwO6UoSGYNP+TzSO/FD/nBCLv4i9Ry84G0Q3JHcUvvcYPlw9b+HPmvr58 TX6w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=m2dmWhXik/U4SGJxPR+hpy5ElrZ2heFLJksoWt01r30=; b=dP1PDxGUOCvLbGTRJU7jgbiQ2upGJ5NTZjk2JDsmUOi9RMUySLOrFhTyirHkxkCzVt YAyCem3bkjafN/tvA6tbwgt2nFwI/mhb5mUn8wP4rJltk/aUEmbx+Kw9VU7EvTIGQ8NS h+eEq6fWjxvgQ8zWwlFb7kpOLtODh0DLM9dwZIx0E4xAKXjVBjcevFvCv8ftCHlNhtIy 0PaCShoPn9elToPcJUy2drvGIjXMp0bhIyYnm18m8rF64sSEpnyvZ7FKn8KBjmTLLOBW Cxpr20j9Gh6ioAH9ytSGk5Etu7xXE0HCuVc6CfeTOPpZyrXsM5ntJfmzsvJNberGRFcm 6Y9w== X-Gm-Message-State: AOAM533Kn0QdOAnHJoQBYvniktuNt5SELkJWwc5wFXhM2CtnvypdskHH OSpaAVbhqKPBydfejEqLGccDgw== X-Google-Smtp-Source: ABdhPJxBqnszFA+50s0l6Us/n0U+kj7hlfE6NXUUWeG9xLlnW3p/P0LMp7yQH8F23/7YGg6koKO3UQ== X-Received: by 2002:a2e:a58e:: with SMTP id m14mr31201325ljp.172.1641375953030; Wed, 05 Jan 2022 01:45:53 -0800 (PST) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id a23sm4137164lfm.235.2022.01.05.01.45.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Jan 2022 01:45:52 -0800 (PST) Received: by box.localdomain (Postfix, from userid 1000) id 3BB3E10425A; Wed, 5 Jan 2022 12:46:11 +0300 (+03) Date: Wed, 5 Jan 2022 12:46:11 +0300 From: "Kirill A. Shutemov" To: Dave Hansen , "David S. Miller" Cc: Borislav Petkov , "Kirill A. Shutemov" , Tom Lendacky , tglx@linutronix.de, mingo@redhat.com, luto@kernel.org, peterz@infradead.org, sathyanarayanan.kuppuswamy@linux.intel.com, aarcange@redhat.com, ak@linux.intel.com, dan.j.williams@intel.com, david@redhat.com, hpa@zytor.com, jgross@suse.com, jmattson@google.com, joro@8bytes.org, jpoimboe@redhat.com, knsathya@kernel.org, pbonzini@redhat.com, sdeep@vmware.com, seanjc@google.com, tony.luck@intel.com, vkuznets@redhat.com, wanpengli@tencent.com, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 19/26] x86/tdx: Make pages shared in ioremap() Message-ID: <20220105094611.kugiarylwjjjttkc@box.shutemov.name> References: <20220103151516.pfcz2pap5l7r2rzv@box.shutemov.name> <20220103181059.ui5eloufw5gsojcb@box.shutemov.name> <20220104191424.oly2gqm4ltzj5wo3@box.shutemov.name> <0e0c38e2-67ad-1f51-c44b-d3c3d505e40a@intel.com> <20220105003108.mr7zyd5oyaaxmnmv@box.shutemov.name> <50dfa0db-fcd1-3c54-d982-237d2c9df431@intel.com> <20220105005720.zdtgwenqwqmuyxvi@box.shutemov.name> <4dc7d5e6-5b35-31ae-b5e9-7c77ed42383b@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4dc7d5e6-5b35-31ae-b5e9-7c77ed42383b@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 04, 2022 at 05:38:25PM -0800, Dave Hansen wrote: > On 1/4/22 4:57 PM, Kirill A. Shutemov wrote: > >> My read of STRICT_MM_TYPECHECKS was that "typedef unsigned long > >> pgprot_t" produces better code, but "typedef struct { unsigned long > >> pgprot; } pgprot_t;" produces better type checking. > > Apart from pgprot_t, __pgprot() and pgrot_val() helpers are defined > > differently depending on STRICT_MM_TYPECHECKS. > > > >> I just compiled these patches on sparc with no issues. > > Hm. I can't see how > > > > #define pgprot_val(x) (x) > > > > can work to access value for the pgprot_t defined as a struct. > > Oh, I must just be compiling with the strict type checks on all the > time. I do really wonder if these are useful these days or if the hacks > were for ancient compilers. > > In any case, this would be pretty easy to fix by just removing the > !STRICT_MM_TYPECHECKS pgprot_val() and defning the STRICT_MM_TYPECHECKS > universally. There's comment in 32-bit Sparc as a reason for STRICT_MM_TYPECHECKS not to be used: /* passing structs on the Sparc slow us down tremendously... */ The comment came from before git times, so I don't know if it still has a merit or newer compilers can deal with it better. bloat-o-meter shows not trivial difference: Total: Before=5342261, After=5344025, chg +0.03% but I'm not sure if it translates into performance loss. David, does the comment still relevant? -- Kirill A. Shutemov