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X-CSE-ConnectionGUID: ZDWBQW/5S+ypRjSK+BFZAw== X-CSE-MsgGUID: FtL+iSRvShSV/EX97aZe+A== X-IronPort-AV: E=McAfee;i="6800,10657,11879"; a="91405640" X-IronPort-AV: E=Sophos;i="6.25,230,1779174000"; d="scan'208";a="91405640" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Aug 2026 14:55:35 -0700 X-CSE-ConnectionGUID: q8bsK/3FSG27OBXQa5SNHw== X-CSE-MsgGUID: n+BNlfg/Q3SPYrOWbvTKGw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,230,1779174000"; d="scan'208";a="262710694" Received: from unknown (HELO [10.24.81.183]) ([10.24.81.183]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Aug 2026 14:55:34 -0700 Message-ID: Date: Tue, 18 Aug 2026 14:55:32 -0700 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 6/6] kvm: Implement SIGSEGV sentinel for Pkey recovery To: Jacky Li , qemu-devel@nongnu.org Cc: Paolo Bonzini , Zhao Liu , Richard Henderson , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Peter Xu , kvm@vger.kernel.org, James Houghton , Mingwei Zhang , Dave Hansen , Brendan Jackman , Reiji Watanabe References: <20260818-feature-pkey-dev-v1-0-8c0ef96a4da9@google.com> <20260818-feature-pkey-dev-v1-6-8c0ef96a4da9@google.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 8/18/26 13:44, Jacky Li wrote: > + if ((fpstate_64->sw_reserved.xstate_bv & XSTATE_PKRU) == 0) { > + return false; > + } Cool stuff! A few little nits on the XSAVE handling. It's subtle, but this wouldn't quite work for pkru when in its init state. I guess the argument is that pkru=0 wouldn't cause a SIGSEGV in the first place so this code wouldn't ever get run. But, if it were me, I'd probably warn or _something_ if I ended up with (xstate_bv&XSTATE_PKRU)==0. I'd probably also at least _check_ for the compacted format. Basically make sure that XCOMP_BV==0, too. This isn't strictly necessary. But it would help me win a bet with a colleague, so would be much appreciated! ;)