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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2B071C388F7 for ; Sun, 25 Oct 2020 09:52:18 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 6997D22284 for ; Sun, 25 Oct 2020 09:52:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="0Sciwr7f" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6997D22284 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B9FC64B985; Sun, 25 Oct 2020 05:52:16 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id fxFF-U3sKhMS; Sun, 25 Oct 2020 05:52:15 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id ABC554B977; Sun, 25 Oct 2020 05:52:15 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 1DE434B93B for ; Sun, 25 Oct 2020 05:52:14 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id MKT9Z5pmB8BD for ; Sun, 25 Oct 2020 05:52:13 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id ECCF64B977 for ; Sun, 25 Oct 2020 05:52:12 -0400 (EDT) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9CB5E22284; Sun, 25 Oct 2020 09:52:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603619531; bh=oAXfvHzROiIAchD8Y3+9mWqjMiIAFBfr4ge5LH7qpEg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=0Sciwr7fKR4KR1rr5vJ8UDM0uTOSzPJ49v+93GOdbuMF1bhiMIt0qT0UaxXdhzuH1 aTjfMKWaTgHjUCHwMpbn8THNc7F7aGkfi6H+W5+KCrUEkKSlidVTOwYlq/iIY/ZcaP CmjOzW1NRC1tDUzWrv3wX5sxqFn1jlxnc5wt0NCs= Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kWch7-0041v2-I6; Sun, 25 Oct 2020 09:52:09 +0000 Date: Sun, 25 Oct 2020 09:52:09 +0000 Message-ID: <871rhmpr92.wl-maz@kernel.org> From: Marc Zyngier To: Gavin Shan Subject: Re: [PATCH 1/3] KVM: arm64: Check if 52-bits PA is enabled In-Reply-To: <20201025002739.5804-2-gshan@redhat.com> References: <20201025002739.5804-1-gshan@redhat.com> <20201025002739.5804-2-gshan@redhat.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26.3 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: gshan@redhat.com, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, will@kernel.org, alexandru.elisei@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Sun, 25 Oct 2020 01:27:37 +0100, Gavin Shan wrote: > > The 52-bits physical address is disabled until CONFIG_ARM64_PA_BITS_52 > is chosen. This uses option for that check, to avoid the unconditional > check on PAGE_SHIFT in the hot path and thus save some CPU cycles. PAGE_SHIFT is known at compile time, and this code is dropped by the compiler if the selected page size is not 64K. This patch really only makes the code slightly less readable and the "CPU cycles" argument doesn't hold at all. So what are you trying to solve exactly? M. > > Signed-off-by: Gavin Shan > --- > arch/arm64/kvm/hyp/pgtable.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 0cdf6e461cbd..fd850353ee89 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -132,8 +132,9 @@ static u64 kvm_pte_to_phys(kvm_pte_t pte) > { > u64 pa = pte & KVM_PTE_ADDR_MASK; > > - if (PAGE_SHIFT == 16) > - pa |= FIELD_GET(KVM_PTE_ADDR_51_48, pte) << 48; > +#ifdef CONFIG_ARM64_PA_BITS_52 > + pa |= FIELD_GET(KVM_PTE_ADDR_51_48, pte) << 48; > +#endif > > return pa; > } > @@ -142,8 +143,9 @@ static kvm_pte_t kvm_phys_to_pte(u64 pa) > { > kvm_pte_t pte = pa & KVM_PTE_ADDR_MASK; > > - if (PAGE_SHIFT == 16) > - pte |= FIELD_PREP(KVM_PTE_ADDR_51_48, pa >> 48); > +#ifdef CONFIG_ARM64_PA_BITS_52 > + pte |= FIELD_PREP(KVM_PTE_ADDR_51_48, pa >> 48); > +#endif > > return pte; > } > -- > 2.23.0 > > -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm