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=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 02953C433DF for ; Mon, 22 Jun 2020 20:09:25 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id B8AE32082F for ; Mon, 22 Jun 2020 20:09:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B8AE32082F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com 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 733204B12F; Mon, 22 Jun 2020 16:09:24 -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 BE29P3N1wSQF; Mon, 22 Jun 2020 16:09:23 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 2C72D4B133; Mon, 22 Jun 2020 16:09:20 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 5A50B4B0F7 for ; Mon, 22 Jun 2020 16:09:19 -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 f+VEhE9tnbp4 for ; Mon, 22 Jun 2020 16:09:16 -0400 (EDT) Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id B14D04B10D for ; Mon, 22 Jun 2020 16:09:13 -0400 (EDT) IronPort-SDR: pfthw1m7SemyHjCR4rllIT5+T1V6x0/Yb6LEEyzM66PYvecefMWyLa1nMbiA02p0OH2T0X/hja 9mLe8iA5Np2g== X-IronPort-AV: E=McAfee;i="6000,8403,9660"; a="142921290" X-IronPort-AV: E=Sophos;i="5.75,268,1589266800"; d="scan'208";a="142921290" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jun 2020 13:09:13 -0700 IronPort-SDR: 6Ia5uhwjctHaySi317F/9+WvPSn+PS6/FHFQk8LIOAcfpdbtUdcjR0PTwaH7efYNEMCOJi2STg cTr2KOvriHeg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,268,1589266800"; d="scan'208";a="318877076" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.152]) by FMSMGA003.fm.intel.com with ESMTP; 22 Jun 2020 13:09:12 -0700 From: Sean Christopherson To: Marc Zyngier , Paolo Bonzini , Arnd Bergmann Subject: [PATCH v2 08/21] KVM: x86/mmu: Clean up the gorilla math in mmu_topup_memory_caches() Date: Mon, 22 Jun 2020 13:08:09 -0700 Message-Id: <20200622200822.4426-9-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.26.0 In-Reply-To: <20200622200822.4426-1-sean.j.christopherson@intel.com> References: <20200622200822.4426-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Cc: linux-arch@vger.kernel.org, Junaid Shahid , Wanpeng Li , kvm@vger.kernel.org, Joerg Roedel , Peter Shier , linux-mips@vger.kernel.org, Sean Christopherson , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Ben Gardon , Vitaly Kuznetsov , Peter Feiner , kvmarm@lists.cs.columbia.edu, Jim Mattson 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 Clean up the minimums in mmu_topup_memory_caches() to document the driving mechanisms behind the minimums. Now that encountering an empty cache is unlikely to trigger BUG_ON(), it is less dangerous to be more precise when defining the minimums. For rmaps, the logic is 1 parent PTE per level, plus a single rmap, and prefetched rmaps. The extra objects in the current '8 + PREFETCH' minimum came about due to an abundance of paranoia in commit c41ef344de212 ("KVM: MMU: increase per-vcpu rmap cache alloc size"), i.e. it could have increased the minimum to 2 rmaps. Furthermore, the unexpected extra rmap case was killed off entirely by commits f759e2b4c728c ("KVM: MMU: avoid pte_list_desc running out in kvm_mmu_pte_write") and f5a1e9f89504f ("KVM: MMU: remove call to kvm_mmu_pte_write from walk_addr"). For the so called page cache, replace '8' with 2*PT64_ROOT_MAX_LEVEL. The 2x multiplier is needed because the cache is used for both shadow pages and gfn arrays for indirect MMUs. And finally, for page headers, replace '4' with PT64_ROOT_MAX_LEVEL. Note, KVM now supports 5-level paging, i.e. the old minimums that used a baseline derived from 4-level paging were technically wrong. But, KVM always allocates roots in a separate flow, e.g. it's impossible in the current implementation to actually need 5 new shadow pages in a single flow. Use PT64_ROOT_MAX_LEVEL unmodified instead of subtracting 1, as the direct usage is likely more intuitive to uninformed readers, and the inflated minimum is unlikely to affect functionality in practice. Reviewed-by: Ben Gardon Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 4b4c3234d623..451e0365e5dd 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1103,14 +1103,17 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu) { int r; + /* 1 rmap, 1 parent PTE per level, and the prefetched rmaps. */ r = mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache, - 8 + PTE_PREFETCH_NUM); + 1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM); if (r) return r; - r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_cache, 8); + r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_cache, + 2 * PT64_ROOT_MAX_LEVEL); if (r) return r; - return mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache, 4); + return mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache, + PT64_ROOT_MAX_LEVEL); } static void mmu_free_memory_caches(struct kvm_vcpu *vcpu) -- 2.26.0 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm