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X-IronPort-AV: E=McAfee;i="6600,9927,10734"; a="346944702" X-IronPort-AV: E=Sophos;i="6.00,226,1681196400"; d="scan'208";a="346944702" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jun 2023 06:50:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10734"; a="1040112788" X-IronPort-AV: E=Sophos;i="6.00,226,1681196400"; d="scan'208";a="1040112788" Received: from swalker-mobl1.amr.corp.intel.com (HELO [10.209.22.184]) ([10.209.22.184]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jun 2023 06:50:19 -0700 Message-ID: <44e1dca7-1071-6d1c-b6d2-c4ca139ab973@intel.com> Date: Thu, 8 Jun 2023 06:50:18 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v11 05/20] x86/virt/tdx: Add SEAMCALL infrastructure Content-Language: en-US To: "Huang, Kai" , "Christopherson,, Sean" , "isaku.yamahata@gmail.com" Cc: "kvm@vger.kernel.org" , "Luck, Tony" , "david@redhat.com" , "bagasdotme@gmail.com" , "ak@linux.intel.com" , "Wysocki, Rafael J" , "kirill.shutemov@linux.intel.com" , "Chatre, Reinette" , "pbonzini@redhat.com" , "linux-mm@kvack.org" , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "Yamahata, Isaku" , "peterz@infradead.org" , "Shahar, Sagi" , "imammedo@redhat.com" , "Gao, Chao" , "Brown, Len" , "sathyanarayanan.kuppuswamy@linux.intel.com" , "Huang, Ying" , "Williams, Dan J" References: <92e19d74-447f-19e0-d9ec-8a3f12f04927@intel.com> <20230607185355.GH2244082@ls.amr.corp.intel.com> <20230607194721.GI2244082@ls.amr.corp.intel.com> <2061ced1-59d7-f21c-490c-b650b7378386@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4CD041A003E X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: zn76s7po8zbamim7cd3mfbzhtpechx7o X-HE-Tag: 1686233386-72066 X-HE-Meta: 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 Npnabkkc sl6kCnR8MjMpGcaG4mc7A0lC4m6YtbL4bCaRZe5XI4um63/E1PhdEfSxNq6JrO02jDMnj/l6nEwlx9KemQDHw5GlFEH6n2PtG9ejeps/ENzlZMX2pe5HL0egwiH277y/jj37t1otHrt5QVnJh/Mnck31gaFuTtPIT8IwyP1jNLQKPDWJOh3urYxeUaonl9KXUNTY8ePvyoNgqReZEPvqMPxl8lX8OaPD19dJ2sD2Shvb38d26yyJdbcqm9uIUAEqjaPY9 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 6/7/23 17:51, Huang, Kai wrote: > How about I add below to the changelog? > > " > The current TDX_MODULE_CALL macro handles neither #GP nor #UD. The kernel would > hit Oops if SEAMCALL were mistakenly made when TDX is enabled by the BIOS or > when CPU isn't in VMX operation. For the former, the callers could check > platform_tdx_enabled() first, although that doesn't rule out the buggy BIOS in > which case the kernel could still get Oops. For the latter, the caller could > check CR4.VMXE based on the fact that currently setting this bit and doing VMXON > are done together when IRQ is disabled, although from hardware's perspective > checking CR4.VMXE isn't enough. > > However this could be problematic if SEAMCALL is called in the cases such as > exception handler, NMI handler, etc, as disabling IRQ doesn't prevent any of > them from happening. > > To have a clean solution, just make the SEAMCALL always return error code by > using EXTTABLE so the SEAMCALL can be safely called in any context. A later > patch will need to use SEAMCALL in the machine check handler. There might be > such use cases in the future too. > " No, that's just word salad. SEAMCALL is like VMRESUME. It's will be called by KVM in unsafe (VMX off) contexts in normal operation like "reboot -f". That means it needs an exception handler for #UD(???). I don't care if a bad BIOS can cause #GP. Bad BIOS == oops. You can argue that even if I don't care, it's worth having a nice error message and a common place for SEAMCALL error handling. But it's not functionally needed.