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 C1BF9C433E1 for ; Fri, 3 Jul 2020 02:37:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A80B5207CD for ; Fri, 3 Jul 2020 02:37:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726776AbgGCChI (ORCPT ); Thu, 2 Jul 2020 22:37:08 -0400 Received: from mga09.intel.com ([134.134.136.24]:3199 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726302AbgGCCgM (ORCPT ); Thu, 2 Jul 2020 22:36:12 -0400 IronPort-SDR: ofqg/agq6OVrXa9brCiN0bJt0SzGcvdtDPJlZEU9SJ2dffqq52Cb+OGiPlaKLak3QkljjvmODV ra1hDoqEG0XQ== X-IronPort-AV: E=McAfee;i="6000,8403,9670"; a="148599906" X-IronPort-AV: E=Sophos;i="5.75,306,1589266800"; d="scan'208";a="148599906" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Jul 2020 19:36:05 -0700 IronPort-SDR: OqHR0HSbM7yCkOBKSIP1TGkeM23HjWL4lGC182DvqArvmODs4cedh/r4bTEtYKA/Lpl8ZV4NiE fXkyUXDrZVpg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,306,1589266800"; d="scan'208";a="278295731" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.152]) by orsmga003.jf.intel.com with ESMTP; 02 Jul 2020 19:36:05 -0700 From: Sean Christopherson To: Marc Zyngier , Paolo Bonzini , Arnd Bergmann Cc: James Morse , Julien Thierry , Suzuki K Poulose , 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, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Ben Gardon , Peter Feiner , Peter Shier , Junaid Shahid , Christoffer Dall Subject: [PATCH v3 05/21] KVM: x86/mmu: Try to avoid crashing KVM if a MMU memory cache is empty Date: Thu, 2 Jul 2020 19:35:29 -0700 Message-Id: <20200703023545.8771-6-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.26.0 In-Reply-To: <20200703023545.8771-1-sean.j.christopherson@intel.com> References: <20200703023545.8771-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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. Reviewed-by: Ben Gardon Signed-off-by: Sean Christopherson --- 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 94b27adab6ba..748235877def 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; } -- 2.26.0