From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 29C6C30D41C for ; Wed, 2 Sep 2026 03:26:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788319580; cv=none; b=Zwe6A5tIvEk3izxvQZWHogv4e+bDRYYl8eSKrCfMa3+mH3DSkBtlu78fGBv6jgtf6faV7pbDht5InxuzBRnqMn94mGyLfwM3Q+vf31aOy5FeIaU4K2TzZydDtQ3u71AG35y8Bd3gwrh6hsWkrEfTEQs6IvQABfGazXXu/WfY+08= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788319580; c=relaxed/simple; bh=drsrORB2aaYMt7PdVCtHE/FS1A9fjTFvIpw03Dx7VC4=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=Hli0dtbOyEbI0BcBVG95yosfv1ST3OPMVXTx4y513g3GPRYkF5BhSRL2nJDjmGdrmZtx7/nZ0d9CxEjzTOPh9dfiRezYpL52aKBtKpbyfZ4ukY4w7iYRmG2jCW8TYTvtuIRlFlDQ4j0U1fQikO24yTt2qqkALXQKZKL0RlSHCKs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=crJHGL2B; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="crJHGL2B" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A76FC1F000E9; Wed, 2 Sep 2026 03:26:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788319578; bh=KFbEThnWxhW00b+oZSbHsimW2fVREGWVwX0n/pGE43A=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=crJHGL2BP7p7JssxzETRncNSBfXX8g0s/mV3Agj7JWkfQSH91GS6vDzRX/zHOasHk vygMldfod+5kTuwRgxnpUpDJdtOiv3HbxTBodoGAoDts5xanBQKpAX5ViRF3PABbWn qeU98QAFsehZhuswhNTyDtPEerrCurJ3qaF7a+TzwJW4XZuodImM3zYyqDg0pahuek eNagrOMxvH1/jCcWiQ1HpM6yLMOVOIKczH19jU59Q1BreSJNiE4fqA5piAq/74XpIb vtJzOh9pONFhmWvSATUJ8ESG7pe/Kf/mpc1N7PRRTau/kJs80+aGYmO5u+HxsvoHzU maTL61JNjJQ0w== From: sashiko-bot@kernel.org Subject: Re: [PATCH v7 02/20] KVM: VMX: Save guest EGPRs in VCPU cache Reply-To: sashiko-reviews@lists.linux.dev To: "Chang S. Bae" Cc: kvm@vger.kernel.org In-Reply-To: <20260902021804.718676-3-chang.seok.bae@intel.com> References: <20260902021804.718676-1-chang.seok.bae@intel.com> <20260902021804.718676-3-chang.seok.bae@intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Wed, 02 Sep 2026 03:26:18 +0000 Message-Id: <20260902032618.A76FC1F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] Host kernel data in Extended General Purpose Registers (EGPRs) is = leaked to a malicious guest via speculative execution when the guest operat= es with APX disabled. -- commit 70442dd137e1b61dbdd5b674afc21cfb7948b2b6 Author: Chang S. Bae KVM: VMX: Save guest EGPRs in VCPU cache This commit saves and restores the guest EGPRs on VM exit/entry if the system supports Advanced Performance Extensions (APX). It skips loading the EGPR state for guests that do not set XCR0[APX], and places the register saving path after SPEC_CTRL is restored. Link: https://lore.kernel.org/adPRA4ZhnvbaXSn0@google.com > diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S > index 00d807505fc88..02308fb36f0f5 100644 > --- a/arch/x86/kvm/vmx/vmenter.S > +++ b/arch/x86/kvm/vmx/vmenter.S [ ... ] > @@ -46,6 +47,16 @@ SYM_FUNC_START(__vmx_vcpu_run) > /* Reload @vmx, _ASM_ARG1 may be modified by vmx_update_host_rsp(). */ > mov WORD_SIZE(%_ASM_SP), %_ASM_DI > =20 > +#ifdef CONFIG_KVM_APX > + ALTERNATIVE "jmp .Lload_egprs_done", "", X86_FEATURE_APX > + testl $KVM_ENTER_EGPR_SWITCH, (%_ASM_SP) > + jz .Lload_egprs_done > + LOAD_REGS %_ASM_DI, VMX_vcpu_arch_regs, \ > + %r16, %r17, %r18, %r19, %r20, %r21, %r22, %r23, \ > + %r24, %r25, %r26, %r27, %r28, %r29, %r30, %r31 > +.Lload_egprs_done: > +#endif [Severity: High] In __vmx_vcpu_run(), when a guest runs with APX disabled, KVM_ENTER_EGPR_SWITCH is clear and this branch skips loading the guest's EGPRs. Are the host's physical %r16 through %r31 register values left intact upon entering the guest when this happens? If so, could a malicious guest with APX disabled speculatively execute APX instructions before the architectural #UD exception retires, allowing it to read the host's %r16 through %r31 values and leak them via a cache side-channel? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260902021804.7186= 76-1-chang.seok.bae@intel.com?part=3D2