From patchwork Mon Jun 22 20:08:09 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 11619029 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1B517138C for ; Mon, 22 Jun 2020 20:13:00 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E8E852073E for ; Mon, 22 Jun 2020 20:12:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="R3iHffu6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8E852073E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-Id:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=IE7+XZCEz8r1AwMnmHztye5b0AFzaPeDlXJgrCR9yGY=; b=R3iHffu6D+CHV/iNm4W8sOJLh AMMHG9o5h4Y4NtP7ognqtpAdewSPv0Us6NZErt2H88n/Aef3jXlDmWRpqF6G1rslYyzZo1RYzmEri Iq3BAedXyJ+73yTVMPPeka2yzM46UJbP5HyLQ+bEzR/HOCO8bGPUbo54erW8V3WPr4k/g1ubqwdQE PPaZ4XKc7lcMT5Hh5rbfMvfzXUCresfwxrWIs//muLrbWxZyxq4FO9UK8i1J3INa3S5HNQMN4pEmX 996qd7iYFoLVMSZODnF8B7asGNoA7Ln80kZ/VYGcYqhIdzcmI8wPU51mNktM7k/mhaoTugvW0MBS2 qwJlAtBNw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jnSmJ-0006Wl-Rp; Mon, 22 Jun 2020 20:10:51 +0000 Received: from mga12.intel.com ([192.55.52.136]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jnSlp-0006Gp-4B for linux-arm-kernel@lists.infradead.org; Mon, 22 Jun 2020 20:10:22 +0000 IronPort-SDR: TDKbpY/k/9tYSHQlzvsonrKJ4P9MASTFyaLnwjQGcanl2Or1CMQVAJZQl0zSpOjmC+4sTwvlx+ OL50CzCrTEqA== X-IronPort-AV: E=McAfee;i="6000,8403,9660"; a="123527733" X-IronPort-AV: E=Sophos;i="5.75,268,1589266800"; d="scan'208";a="123527733" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga106.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 X-Spam-Note: CRM114 invocation failed X-Spam-Score: -2.3 (--) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-2.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [192.55.52.136 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.0 SPF_HELO_PASS SPF: HELO matches SPF record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Junaid Shahid , Christoffer Dall , Wanpeng Li , kvm@vger.kernel.org, Suzuki K Poulose , Joerg Roedel , Peter Shier , linux-mips@vger.kernel.org, Sean Christopherson , linux-kernel@vger.kernel.org, James Morse , linux-arm-kernel@lists.infradead.org, Ben Gardon , Vitaly Kuznetsov , Peter Feiner , kvmarm@lists.cs.columbia.edu, Julien Thierry , Jim Mattson Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org 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)