From patchwork Fri Jun 5 21:38:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 11590583 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 E4DAA175A for ; Fri, 5 Jun 2020 21:39:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D52B220772 for ; Fri, 5 Jun 2020 21:39:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728638AbgFEVjR (ORCPT ); Fri, 5 Jun 2020 17:39:17 -0400 Received: from mga17.intel.com ([192.55.52.151]:49312 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728430AbgFEVjK (ORCPT ); Fri, 5 Jun 2020 17:39:10 -0400 IronPort-SDR: FgRI+HSH1GkyhhIzWvk460hY2SYP/uvQn4p2OqVE5DPPT0+LJH55GeX+1Ji3hPrI2EPs+eJCJ6 9JaxJKmr1i9A== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Jun 2020 14:39:08 -0700 IronPort-SDR: /DIB9oiqYI2Fg3zD1AVI7xOqUEPZThNOBLFZjDo1clHWgdOMBdzQcqRgIJ9S8j4GwRp7A7TrVS UbqM0qM5y0jg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,477,1583222400"; d="scan'208";a="287860880" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.152]) by orsmga002.jf.intel.com with ESMTP; 05 Jun 2020 14:39:07 -0700 From: Sean Christopherson To: Marc Zyngier , Paul Mackerras , Christian Borntraeger , Janosch Frank , Paolo Bonzini Cc: James Morse , Julien Thierry , Suzuki K Poulose , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Feiner , Peter Shier , Junaid Shahid , Ben Gardon , Christoffer Dall Subject: [PATCH 05/21] KVM: x86/mmu: Try to avoid crashing KVM if a MMU memory cache is empty Date: Fri, 5 Jun 2020 14:38:37 -0700 Message-Id: <20200605213853.14959-6-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.26.0 In-Reply-To: <20200605213853.14959-1-sean.j.christopherson@intel.com> References: <20200605213853.14959-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Attempt to allocate a new object instead of crashing KVM (and likely the kernel) if a memory cache is unexpectedly empty. Use GFP_ATOMIC for the allocation as the caches are used while holding mmu_lock. The immediate BUG_ON() makes the code unnecessarily explosive and led to confusing minimums being used in the past, e.g. allocating 4 objects where 1 would suffice. Signed-off-by: Sean Christopherson Reviewed-by: Ben Gardon --- arch/x86/kvm/mmu/mmu.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index ba70de24a5b0..5e773564ab20 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1060,6 +1060,15 @@ static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu) local_irq_enable(); } +static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc, + gfp_t gfp_flags) +{ + if (mc->kmem_cache) + return kmem_cache_zalloc(mc->kmem_cache, gfp_flags); + else + return (void *)__get_free_page(gfp_flags); +} + static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min) { void *obj; @@ -1067,10 +1076,7 @@ static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min) if (mc->nobjs >= min) return 0; while (mc->nobjs < ARRAY_SIZE(mc->objects)) { - if (mc->kmem_cache) - obj = kmem_cache_zalloc(mc->kmem_cache, GFP_KERNEL_ACCOUNT); - else - obj = (void *)__get_free_page(GFP_KERNEL_ACCOUNT); + obj = mmu_memory_cache_alloc_obj(mc, GFP_KERNEL_ACCOUNT); if (!obj) return mc->nobjs >= min ? 0 : -ENOMEM; mc->objects[mc->nobjs++] = obj; @@ -1118,8 +1124,11 @@ static void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc) { void *p; - BUG_ON(!mc->nobjs); - p = mc->objects[--mc->nobjs]; + if (WARN_ON(!mc->nobjs)) + p = mmu_memory_cache_alloc_obj(mc, GFP_ATOMIC | __GFP_ACCOUNT); + else + p = mc->objects[--mc->nobjs]; + BUG_ON(!p); return p; }