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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 0A403C4338F for ; Wed, 11 Aug 2021 09:36:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DF4D76056C for ; Wed, 11 Aug 2021 09:36:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236727AbhHKJhM (ORCPT ); Wed, 11 Aug 2021 05:37:12 -0400 Received: from foss.arm.com ([217.140.110.172]:46128 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236705AbhHKJhK (ORCPT ); Wed, 11 Aug 2021 05:37:10 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D657D113E; Wed, 11 Aug 2021 02:36:46 -0700 (PDT) Received: from [10.163.67.241] (unknown [10.163.67.241]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 736E53F70D; Wed, 11 Aug 2021 02:36:44 -0700 (PDT) Subject: Re: [PATCH 1/5] KVM: arm64: Drop direct PAGE_[SHIFT|SIZE] usage as page size To: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, James Morse , Alexandru Elisei , Suzuki K Poulose , Catalin Marinas , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org References: <1628578961-29097-1-git-send-email-anshuman.khandual@arm.com> <1628578961-29097-2-git-send-email-anshuman.khandual@arm.com> <25ee7799069492f2501003faec7f9732@kernel.org> <0b47c654-7e9b-a7ca-bdf4-f9607062200e@arm.com> <87zgto9z9i.wl-maz@kernel.org> From: Anshuman Khandual Message-ID: <4a4d320e-f09c-5198-d3cb-397d837190b1@arm.com> Date: Wed, 11 Aug 2021 15:07:36 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <87zgto9z9i.wl-maz@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/11/21 1:41 PM, Marc Zyngier wrote: > On Wed, 11 Aug 2021 06:34:46 +0100, > Anshuman Khandual wrote: >> >> >> >> On 8/10/21 7:03 PM, Marc Zyngier wrote: >>> On 2021-08-10 08:02, Anshuman Khandual wrote: >>>> All instances here could just directly test against CONFIG_ARM64_XXK_PAGES >>>> instead of evaluating via PAGE_SHIFT or PAGE_SIZE. With this change, there >>>> will be no such usage left. >>>> >>>> Cc: Marc Zyngier >>>> Cc: James Morse >>>> Cc: Alexandru Elisei >>>> Cc: Suzuki K Poulose >>>> Cc: Catalin Marinas >>>> Cc: Will Deacon >>>> Cc: linux-arm-kernel@lists.infradead.org >>>> Cc: kvmarm@lists.cs.columbia.edu >>>> Cc: linux-kernel@vger.kernel.org >>>> Signed-off-by: Anshuman Khandual >>>> --- >>>>  arch/arm64/kvm/hyp/pgtable.c | 6 +++--- >>>>  arch/arm64/mm/mmu.c          | 2 +- >>>>  2 files changed, 4 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c >>>> index 05321f4165e3..a6112b6d6ef6 100644 >>>> --- a/arch/arm64/kvm/hyp/pgtable.c >>>> +++ b/arch/arm64/kvm/hyp/pgtable.c >>>> @@ -85,7 +85,7 @@ static bool kvm_level_supports_block_mapping(u32 level) >>>>       * Reject invalid block mappings and don't bother with 4TB mappings for >>>>       * 52-bit PAs. >>>>       */ >>>> -    return !(level == 0 || (PAGE_SIZE != SZ_4K && level == 1)); >>>> +    return !(level == 0 || (!IS_ENABLED(CONFIG_ARM64_4K_PAGES) && level == 1)); >>>>  } >>>> >>>>  static bool kvm_block_mapping_supported(u64 addr, u64 end, u64 phys, u32 level) >>>> @@ -155,7 +155,7 @@ static u64 kvm_pte_to_phys(kvm_pte_t pte) >>>>  { >>>>      u64 pa = pte & KVM_PTE_ADDR_MASK; >>>> >>>> -    if (PAGE_SHIFT == 16) >>>> +    if (IS_ENABLED(CONFIG_ARM64_64K_PAGES)) >>>>          pa |= FIELD_GET(KVM_PTE_ADDR_51_48, pte) << 48; >>>> >>>>      return pa; >>>> @@ -165,7 +165,7 @@ static kvm_pte_t kvm_phys_to_pte(u64 pa) >>>>  { >>>>      kvm_pte_t pte = pa & KVM_PTE_ADDR_MASK; >>>> >>>> -    if (PAGE_SHIFT == 16) >>>> +    if (IS_ENABLED(CONFIG_ARM64_64K_PAGES)) >>>>          pte |= FIELD_PREP(KVM_PTE_ADDR_51_48, pa >> 48); >>>> >>>>      return pte; >>>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>>> index 9ff0de1b2b93..8fdfca179815 100644 >>>> --- a/arch/arm64/mm/mmu.c >>>> +++ b/arch/arm64/mm/mmu.c >>>> @@ -296,7 +296,7 @@ static void alloc_init_cont_pmd(pud_t *pudp, >>>> unsigned long addr, >>>>  static inline bool use_1G_block(unsigned long addr, unsigned long next, >>>>              unsigned long phys) >>>>  { >>>> -    if (PAGE_SHIFT != 12) >>>> +    if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES)) >>>>          return false; >>>> >>>>      if (((addr | next | phys) & ~PUD_MASK) != 0) >>> >>> I personally find it a lot less readable. >>> >>> Also, there is no evaluation whatsoever. All the code guarded >>> by a PAGE_SIZE/PAGE_SHIFT that doesn't match the configuration >>> is dropped at compile time. >> >> The primary idea here is to unify around IS_ENABLED(CONFIG_ARM64_XXK_PAGES) >> usage in arm64, rather than having multiple methods to test page size when >> ever required. > > I'm sorry, but I find the idiom extremely painful to parse. If you are Okay, it was not explained very well. My bad. > annoyed with the 'PAGE_SHIFT == 12/14/16', consider replacing it with > 'PAGE_SIZE == SZ_4/16/64K' instead. Sure, understood. But the problem here is not with PAGE_SHIFT/PAGE_SIZE based tests but rather having multiple ways of doing the same thing in arm64 tree. Please find further explanation below. > > IS_ENABLED(CONFIG_ARM64_XXK_PAGES) also gives the wrong impression > that *multiple* page sizes can be selected at any given time. That's > obviously not the case, which actually makes PAGE_SIZE a much better > choice. PAGE_SHIFT and PAGE_SIZE are derived from CONFIG_ARM64_XXK_PAGES. Hence why not just directly use the original user selected config option that eventually decides PAGE_SHIFT and PAGE_SIZE. config ARM64_PAGE_SHIFT int default 16 if ARM64_64K_PAGES default 14 if ARM64_16K_PAGES default 12 arch/arm64/include/asm/page-def.h:#define PAGE_SHIFT CONFIG_ARM64_PAGE_SHIFT arch/arm64/include/asm/page-def.h:#define PAGE_SIZE (_AC(1, UL) << PAGE_SHIFT) Also there are already similar IS_ENABLED() instances which do not create much confusion. The point here being, to have just a single method that checks compiled page size support, instead of three different ways of doing the same thing. - IS_ENABLED(CONFIG_ARM64_XXK_PAGES) - if (PAGE_SHIFT == XX) - if (PAGE_SIZE == XX) $git grep IS_ENABLED arch/arm64/ | grep PAGES arch/arm64/include/asm/vmalloc.h: return IS_ENABLED(CONFIG_ARM64_4K_PAGES) && arch/arm64/mm/mmu.c: BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES)); arch/arm64/mm/mmu.c: BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES)); > > As things stand, I don't plan to take such a patch. Sure, will drop it from the series if the above explanation and the rationale for the patch still does not convince you. > > Thanks, > > M. >