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X-CSE-ConnectionGUID: x9jK8aDVTc2HEE4Jgp2XmQ== X-CSE-MsgGUID: svptJn5eSzWs7Z7qqjek/w== X-IronPort-AV: E=McAfee;i="6700,10204,11419"; a="46804537" X-IronPort-AV: E=Sophos;i="6.15,251,1739865600"; d="scan'208";a="46804537" Received: from orviesa007.jf.intel.com ([10.64.159.147]) by fmvoesa113.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Apr 2025 08:02:10 -0700 X-CSE-ConnectionGUID: XQEaiVrUS4u/1iDHzMo2IQ== X-CSE-MsgGUID: Uj0jWxUVSl6Vk9/94rgppA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.15,251,1739865600"; d="scan'208";a="134649851" Received: from tfalcon-desk.amr.corp.intel.com (HELO [10.124.223.193]) ([10.124.223.193]) by orviesa007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Apr 2025 08:02:08 -0700 Message-ID: Date: Wed, 30 Apr 2025 08:02:05 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [V2 PATCH] x86/tdx: add VIRT_CPUID2 virtualization if REDUCE_VE was not successful To: Zhiquan Li , Jun Miao , kirill.shutemov@linux.intel.com, dave.hansen@linux.intel.com Cc: x86@kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, "Du, Fan" References: <20250429143114.1724280-1-jun.miao@intel.com> <20250429143114.1724280-2-jun.miao@intel.com> <0e298f80-5361-4376-a099-d3457c8cd349@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/30/25 08:09, Zhiquan Li wrote: > On 2025/4/30 21:44, Dave Hansen wrote: >>> Currently the most customer's complaints come from the CPUID leaf 0x2 >>> not virtualization, and most of access come from user space. Is it >>> appropriate for such behavior directly cause a guest kernel panic? >> If a VMM doesn't properly configure topology properly and allows >> REDUCE_VE, then panic. They obviously got something wrong because that >> configuration doesn't make any sense. > OK, I agree with you. Is it better to simplify the logic like this: > > static void reduce_unnecessary_ve(void) > { > u64 configured; > > /* Has the VMM provided a valid topology configuration? */ > tdg_vm_rd(TDCS_TOPOLOGY_ENUM_CONFIGURED, &configured); > > if (!configured) > panic("VMM did not configure X2APIC_IDs properly\n"); > > tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_REDUCE_VE, TD_CTLS_REDUCE_VE); > } > > Since merely fall back to enable ENUM_TOPOLOGY isn't enough, the guest > still suffering the CPUID leaf 0x2 not virtualization regression, like > the glibc bug. Full REDUCE_VE is really expected. Either that or fix the TDX module in some way to untangle the mess.