From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BDD5C433F5 for ; Tue, 2 Nov 2021 17:17:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 628A861052 for ; Tue, 2 Nov 2021 17:17:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230214AbhKBRU2 (ORCPT ); Tue, 2 Nov 2021 13:20:28 -0400 Received: from mail.skyhub.de ([5.9.137.197]:55782 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229684AbhKBRUU (ORCPT ); Tue, 2 Nov 2021 13:20:20 -0400 Received: from zn.tnic (p200300ec2f0f6200599060f0a067c463.dip0.t-ipconnect.de [IPv6:2003:ec:2f0f:6200:5990:60f0:a067:c463]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 0B5881EC011B; Tue, 2 Nov 2021 18:17:44 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1635873464; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=3k4UAR3waP1O7QGWGVCIvAvoqbPAyUfbTyj8oUzmI68=; b=SeyOgVQjj3BQhQf5sHXtuXpKsQ++nRNdi9c43JfJi45//PBZmGZ8tAHWFoXXTFS75b2FpU nifTwIFZsxidse9XB6WTzJ0MaQjjwyO8b0Nw3BSrGpJb9FoM8urYmB4pdNQ7nUzDej/dYg k/eADB0zWg+TZRUOYZNnV0PKhD0DvbM= Date: Tue, 2 Nov 2021 18:17:39 +0100 From: Borislav Petkov To: "Eric W. Biederman" Cc: Joerg Roedel , x86@kernel.org, kexec@lists.infradead.org, Joerg Roedel , stable@vger.kernel.org, hpa@zytor.com, Andy Lutomirski , Dave Hansen , Peter Zijlstra , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , Kees Cook , David Rientjes , Cfir Cohen , Erdem Aktas , Masami Hiramatsu , Mike Stunes , Sean Christopherson , Martin Radev , Arvind Sankar , linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v2 01/12] kexec: Allow architecture code to opt-out at runtime Message-ID: References: <20210913155603.28383-1-joro@8bytes.org> <20210913155603.28383-2-joro@8bytes.org> <87pmrjbmy9.fsf@disp2133> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87pmrjbmy9.fsf@disp2133> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 01, 2021 at 04:11:42PM -0500, Eric W. Biederman wrote: > I seem to remember the consensus when this was reviewed that it was > unnecessary and there is already support for doing something like > this at a more fine grained level so we don't need a new kexec hook. Well, the executive summary is that you have a guest whose memory *and* registers are encrypted so the hypervisor cannot have a poke inside and reset the vCPU like it would normally do. So you need to do that dance differently, i.e, the patchset. If you try to kexec such a guest now, it'll init only the BSP, as Joerg said. So I guess a single-threaded kdump. And yes, one of the prominent use cases is kdumping from such a guest, as distros love doing kdump for debugging. I hope that explains it better. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette