From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7B1BE72 for ; Thu, 15 Jul 2021 07:40:09 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id A07AC2279C; Thu, 15 Jul 2021 07:40:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1626334801; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5JMBVUc1fC80+7deLYH6ZLQZq/uUCL7N+S0Ckg+qtbI=; b=Twb6x088Ds05jfTu5/IB5porBtTYCy7ypb/AOBkBIcuTOW8D+d7upMLB1l3nohEF7iPW/p 8deiq9K1vIvBrAZjm5PrzzYiClmYOaPP+BfxFaSOoAZgjQKRVJE/jYn3GYYxV/6Wzn5j3A OCFRqAN5FYIib3+LRrkkcU505ZTakD0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1626334801; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5JMBVUc1fC80+7deLYH6ZLQZq/uUCL7N+S0Ckg+qtbI=; b=iCqY9l43TypCWFiyhhci4MfAifGCRh3LrqaNuvVgpKgYxC55KpqRWrvVubNKGrttlJ8kft DVVygz62vy0zvcDA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 7FEF413C2C; Thu, 15 Jul 2021 07:40:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id teNrHVDm72BeZwAAMHmgww (envelope-from ); Thu, 15 Jul 2021 07:40:00 +0000 Date: Thu, 15 Jul 2021 09:39:58 +0200 From: Joerg Roedel To: Sean Christopherson Cc: Brijesh Singh , x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , tony.luck@intel.com, npmccallum@redhat.com, brijesh.ksingh@gmail.com Subject: Re: [PATCH Part2 RFC v4 01/40] KVM: SVM: Add support to handle AP reset MSR protocol Message-ID: References: <20210707183616.5620-1-brijesh.singh@amd.com> <20210707183616.5620-2-brijesh.singh@amd.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Jul 14, 2021 at 08:17:29PM +0000, Sean Christopherson wrote: > On Wed, Jul 07, 2021, Brijesh Singh wrote: > > From: Tom Lendacky > > > > Add support for AP Reset Hold being invoked using the GHCB MSR protocol, > > available in version 2 of the GHCB specification. > > Please provide a brief overview of the protocol, and why it's needed. I assume > it's to allow AP wakeup without a shared GHCB? Yes, this is needed for SEV-ES kexec support to park APs without the need for memory that will be owned by the new kernel when APs are woken up. You can have a look into my SEV-ES kexec/kdump patch-set for details: https://lore.kernel.org/lkml/20210705082443.14721-1-joro@8bytes.org/ I also sent this patch separatly earlier this week to enable GHCB protocol version 2 support in KVM. Regards, Joerg