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X-CSE-ConnectionGUID: 5B6I6+rQT02gu9BJFixR7A== X-CSE-MsgGUID: 7Z2E12F8QMeDLaAPpaX31Q== X-IronPort-AV: E=McAfee;i="6700,10204,11406"; a="45653154" X-IronPort-AV: E=Sophos;i="6.15,219,1739865600"; d="scan'208";a="45653154" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by fmvoesa113.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Apr 2025 10:50:08 -0700 X-CSE-ConnectionGUID: /DOnGeQQRRaAeKUHOOaJhg== X-CSE-MsgGUID: wnT8KGPgTK+Vq6cci1YFNQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.15,219,1739865600"; d="scan'208";a="135995936" Received: from bjrankin-mobl3.amr.corp.intel.com (HELO [10.124.223.169]) ([10.124.223.169]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Apr 2025 10:50:07 -0700 Message-ID: <7bd03311-0c4c-41e6-b6dc-803b6455f170@intel.com> Date: Thu, 17 Apr 2025 10:50:06 -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: [PATCH] x86/virt/tdx: Make TDX and kexec mutually exclusive at runtime To: Kai Huang , bp@alien8.de, tglx@linutronix.de, peterz@infradead.org, mingo@redhat.com Cc: kirill.shutemov@linux.intel.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, seanjc@google.com, rick.p.edgecombe@intel.com, reinette.chatre@intel.com, isaku.yamahata@intel.com, dan.j.williams@intel.com, thomas.lendacky@amd.com, ashish.kalra@amd.com, nik.borisov@suse.com, sagis@google.com References: <20250416230259.97989-1-kai.huang@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 4/16/25 16:02, Kai Huang wrote: > Full support for kexec on a TDX host would require complex work. > The cache flushing required would need to happen while stopping > remote CPUs, which would require changes to a fragile area of the > kernel. Doesn't kexec already stop remote CPUs? Doesn't this boil down to a WBINVD? How is that complex? > It would also require resetting TDX private pages, which is non- > trivial since the core kernel does not track them. Why? The next kernel will just use KeyID-0 which will blast the old pages away with no side effects... right? > Lastly, it would have to rely on a yet-to-be documented behavior > around the TME key (KeyID 0). I'll happily wait for the documentation if you insist on it (I don't).