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21 Nov 2022 14:00:19 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10538"; a="886277273" X-IronPort-AV: E=Sophos;i="5.96,182,1665471600"; d="scan'208";a="886277273" Received: from dylanhol-mobl.amr.corp.intel.com (HELO [10.212.242.103]) ([10.212.242.103]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Nov 2022 14:00:16 -0800 Message-ID: Date: Mon, 21 Nov 2022 14:00:14 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.4.2 Subject: Re: [PATCH v7 03/20] x86/virt/tdx: Disable TDX if X2APIC is not enabled Content-Language: en-US To: "Huang, Kai" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Cc: "Hansen, Dave" , "Luck, Tony" , "bagasdotme@gmail.com" , "ak@linux.intel.com" , "Wysocki, Rafael J" , "kirill.shutemov@linux.intel.com" , "Christopherson,, Sean" , "Chatre, Reinette" , "pbonzini@redhat.com" , "linux-mm@kvack.org" , "Yamahata, Isaku" , "peterz@infradead.org" , "Shahar, Sagi" , "imammedo@redhat.com" , "Gao, Chao" , "Brown, Len" , "Huang, Ying" , "Williams, Dan J" References: <62c67ed3-e4d1-082f-800a-b0837c9432a9@linux.intel.com> <31cb1df3cf21889fb33a7c675aa1bf5fa2078cad.camel@intel.com> From: Sathyanarayanan Kuppuswamy In-Reply-To: <31cb1df3cf21889fb33a7c675aa1bf5fa2078cad.camel@intel.com> Content-Type: text/plain; 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bh=JvBbrJsG/05t2k1v3pcj/TY3qVXVaPPBcSSJUvRYeyQ=; b=Z8OuY267IhsQXOAiz2xUz6Kl7eFCQxIwQRssJllnmXnV1a5+MQSyyr/I5KGm+Et9tlX9Qt kwMl4+Bc/o4O/3ReqbpZfSN9cEgzrRGup2btolLG1encevRQuhoqScN5ol8u8FxEcCFxvs BN0ojSpyCjJuf7gn2p5p2z8zG9kbueI= X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 3E51F1C0018 Authentication-Results: imf18.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=i3qIMkJd; spf=none (imf18.hostedemail.com: domain of sathyanarayanan.kuppuswamy@linux.intel.com has no SPF policy when checking 192.55.52.115) smtp.mailfrom=sathyanarayanan.kuppuswamy@linux.intel.com; dmarc=fail reason="No valid SPF" header.from=intel.com (policy=none) X-Rspam-User: X-Stat-Signature: n1hc6dijanbdccezz34ingr9r7qbijiu X-HE-Tag: 1669068020-951930 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11/21/22 1:44 AM, Huang, Kai wrote: > On Sun, 2022-11-20 at 19:51 -0800, Sathyanarayanan Kuppuswamy wrote: >> >> On 11/20/22 4:26 PM, Kai Huang wrote: >>> The MMIO/xAPIC interface has some problems, most notably the APIC LEAK >> >> "some problems" looks more generic. May be we can be specific here. Like >> it has security issues? > > It was quoted from below upstream commit id (I only kept the one that I quoted > to save space): Ok. > > commit b8d1d163604bd1e600b062fb00de5dc42baa355f (tag: x86_apic_for_v6.1_rc1, > tip/x86/apic) > Author: Daniel Sneddon > Date: Tue Aug 16 16:19:42 2022 -0700 > > x86/apic: Don't disable x2APIC if locked > > .... > > The MMIO/xAPIC interface has some problems, most notably the APIC LEAK > [1]. This bug allows an attacker to use the APIC MMIO interface to > extract data from the SGX enclave. > > .... > > [1]: https://aepicleak.com/aepicleak.pdf > > Signed-off-by: Daniel Sneddon > Signed-off-by: Dave Hansen > Acked-by: Dave Hansen > Tested-by: Neelima Krishnan > Link: > https://lkml.kernel.org/r/20220816231943.1152579-1-daniel.sneddon@linux.intel.com > > >> >>> [1]. This bug allows an attacker to use the APIC MMIO interface to >>> extract data from the SGX enclave. >>> >>> TDX is not immune from this either. Early check X2APIC and disable TDX >>> if X2APIC is not enabled, and make INTEL_TDX_HOST depend on X86_X2APIC. >>> >>> [1]: https://aepicleak.com/aepicleak.pdf >>> >>> Link: https://lore.kernel.org/lkml/d6ffb489-7024-ff74-bd2f-d1e06573bb82@intel.com/ >>> Link: https://lore.kernel.org/lkml/ba80b303-31bf-d44a-b05d-5c0f83038798@intel.com/ >>> Signed-off-by: Kai Huang >>> --- >>> >>> v6 -> v7: >>> - Changed to use "Link" for the two lore links to get rid of checkpatch >>> warning. >>> >>> --- >>> arch/x86/Kconfig | 1 + >>> arch/x86/virt/vmx/tdx/tdx.c | 11 +++++++++++ >>> 2 files changed, 12 insertions(+) >>> >>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>> index cced4ef3bfb2..dd333b46fafb 100644 >>> --- a/arch/x86/Kconfig >>> +++ b/arch/x86/Kconfig >>> @@ -1958,6 +1958,7 @@ config INTEL_TDX_HOST >>> depends on CPU_SUP_INTEL >>> depends on X86_64 >>> depends on KVM_INTEL >>> + depends on X86_X2APIC >>> help >>> Intel Trust Domain Extensions (TDX) protects guest VMs from malicious >>> host and certain physical attacks. This option enables necessary TDX >>> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c >>> index 982d9c453b6b..8d943bdc8335 100644 >>> --- a/arch/x86/virt/vmx/tdx/tdx.c >>> +++ b/arch/x86/virt/vmx/tdx/tdx.c >>> @@ -12,6 +12,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> #include >>> #include "tdx.h" >>> >>> @@ -81,6 +82,16 @@ static int __init tdx_init(void) >>> goto no_tdx; >>> } >>> >>> + /* >>> + * TDX requires X2APIC being enabled to prevent potential data >>> + * leak via APIC MMIO registers. Just disable TDX if not using >>> + * X2APIC. >> >> Remove the double space. > > Sorry which "double space"? Before Just disable. It looked like double space. Is it not? > >> >>> + */ >>> + if (!x2apic_enabled()) { >>> + pr_info("Disable TDX as X2APIC is not enabled.\n"); >> >> pr_warn()? > > Why? Since it is a failure case, I thought pr_warn would be better. It is up to you. > -- Sathyanarayanan Kuppuswamy Linux Kernel Developer