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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7558AC4332F for ; Wed, 9 Feb 2022 18:57:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241431AbiBIS51 (ORCPT ); Wed, 9 Feb 2022 13:57:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241362AbiBIS4t (ORCPT ); Wed, 9 Feb 2022 13:56:49 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 60914C0401D1; Wed, 9 Feb 2022 10:56:44 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id F3C97612CC; Wed, 9 Feb 2022 18:56:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 505EFC340E7; Wed, 9 Feb 2022 18:56:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1644433003; bh=VJ/N0JazzuRmFU1tDsAyHVrOmtuD8Q3QOGqJ9jK6NJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aX9OPgo4Wtr2kJWHHpBEMImaHBvJCnjlINll1tc6wAFiXxzQYLvwbgdcU6l4S66/T MtgUSwzN4/u3lMGRrk2i/EZhmFifrL1l8nqo/Dvk7AzcOqCSmzHywzkTLmJiQqkIxi cB3ggApE+DqXv6KDbCTjEm3J4PN1MXXpj0kM2wTiLlhrKCW33KXQUiO0TKvMWITbDU puChYEht6z7S5KRvdJsdfukUdFFAll9I/IEKmEeoIwtMFNwOhHxikmBLpIWR7qPkMl rCLsorMZKgrEIA5C1HL0PwrneQYVBaqBmkueIt8CJC1aM6rmzYVWuNmJvBJunMfMXX iUnR1aRPPFLgw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sean Christopherson , Paolo Bonzini , Sasha Levin , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org Subject: [PATCH MANUALSEL 5.16 4/8] KVM: nVMX: WARN on any attempt to allocate shadow VMCS for vmcs02 Date: Wed, 9 Feb 2022 13:56:30 -0500 Message-Id: <20220209185635.48730-4-sashal@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220209185635.48730-1-sashal@kernel.org> References: <20220209185635.48730-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Sean Christopherson [ Upstream commit d6e656cd266cdcc95abd372c7faef05bee271d1a ] WARN if KVM attempts to allocate a shadow VMCS for vmcs02. KVM emulates VMCS shadowing but doesn't virtualize it, i.e. KVM should never allocate a "real" shadow VMCS for L2. The previous code WARNed but continued anyway with the allocation, presumably in an attempt to avoid NULL pointer dereference. However, alloc_vmcs (and hence alloc_shadow_vmcs) can fail, and indeed the sole caller does: if (enable_shadow_vmcs && !alloc_shadow_vmcs(vcpu)) goto out_shadow_vmcs; which makes it not a useful attempt. Signed-off-by: Sean Christopherson Message-Id: <20220125220527.2093146-1-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kvm/vmx/nested.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index c605c2c01394b..9cd68e1fcf602 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -4827,18 +4827,20 @@ static struct vmcs *alloc_shadow_vmcs(struct kvm_vcpu *vcpu) struct loaded_vmcs *loaded_vmcs = vmx->loaded_vmcs; /* - * We should allocate a shadow vmcs for vmcs01 only when L1 - * executes VMXON and free it when L1 executes VMXOFF. - * As it is invalid to execute VMXON twice, we shouldn't reach - * here when vmcs01 already have an allocated shadow vmcs. + * KVM allocates a shadow VMCS only when L1 executes VMXON and frees it + * when L1 executes VMXOFF or the vCPU is forced out of nested + * operation. VMXON faults if the CPU is already post-VMXON, so it + * should be impossible to already have an allocated shadow VMCS. KVM + * doesn't support virtualization of VMCS shadowing, so vmcs01 should + * always be the loaded VMCS. */ - WARN_ON(loaded_vmcs == &vmx->vmcs01 && loaded_vmcs->shadow_vmcs); + if (WARN_ON(loaded_vmcs != &vmx->vmcs01 || loaded_vmcs->shadow_vmcs)) + return loaded_vmcs->shadow_vmcs; + + loaded_vmcs->shadow_vmcs = alloc_vmcs(true); + if (loaded_vmcs->shadow_vmcs) + vmcs_clear(loaded_vmcs->shadow_vmcs); - if (!loaded_vmcs->shadow_vmcs) { - loaded_vmcs->shadow_vmcs = alloc_vmcs(true); - if (loaded_vmcs->shadow_vmcs) - vmcs_clear(loaded_vmcs->shadow_vmcs); - } return loaded_vmcs->shadow_vmcs; } -- 2.34.1