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Biederman) To: Joerg Roedel References: <20210506093122.28607-1-joro@8bytes.org> <20210506093122.28607-3-joro@8bytes.org> Date: Thu, 06 May 2021 12:42:03 -0500 In-Reply-To: <20210506093122.28607-3-joro@8bytes.org> (Joerg Roedel's message of "Thu, 6 May 2021 11:31:22 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1lei0m-0003nZ-2F; ; ; mid=; ; ; hst=in01.mta.xmission.com; ; ; ip=68.227.160.95; ; ; frm=ebiederm@xmission.com; ; ; spf=neutral X-XM-AID: U2FsdGVkX18K6SvQ88nM/nPpaU9bp8QcNl7ZXSm1Ea8= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 2/2] x86/kexec/64: Forbid kexec when running as an SEV-ES guest X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Cc: kvm@vger.kernel.org, Peter Zijlstra , Dave Hansen , virtualization@lists.linux-foundation.org, Arvind Sankar , hpa@zytor.com, Jiri Slaby , x86@kernel.org, David Rientjes , Martin Radev , Tom Lendacky , Joerg Roedel , Kees Cook , Cfir Cohen , linux-coco@lists.linux.dev, Andy Lutomirski , Dan Williams , Juergen Gross , Mike Stunes , Sean Christopherson , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Masami Hiramatsu , Erdem Aktas X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" Joerg Roedel writes: > From: Joerg Roedel > > For now, kexec is not supported when running as an SEV-ES guest. Doing > so requires additional hypervisor support and special code to hand > over the CPUs to the new kernel in a safe way. > > Until this is implemented, do not support kexec in SEV-ES guests. I don't understand this. Fundamentally kexec is about doing things more or less inspite of what the firmware is doing. I don't have any idea what a SEV-ES is. But the normal x86 boot doesn't do anything special. Is cross cpu IPI emulation buggy? If this is a move in your face hypervisor like Xen is sometimes I can see perhaps needing a little bit of different work during bootup. Perhaps handing back a cpu on system shutdown and asking for more cpus on system boot up. What is the actual problem you are trying to avoid? And yes for a temporary hack the suggestion of putting code into machine_kexec_prepare seems much more reasonable so we don't have to carry special case infrastructure for the forseeable future. Eric > Cc: stable@vger.kernel.org # v5.10+ > Signed-off-by: Joerg Roedel > --- > arch/x86/kernel/machine_kexec_64.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c > index c078b0d3ab0e..f902cc9cc634 100644 > --- a/arch/x86/kernel/machine_kexec_64.c > +++ b/arch/x86/kernel/machine_kexec_64.c > @@ -620,3 +620,11 @@ void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) > */ > set_memory_encrypted((unsigned long)vaddr, pages); > } > + > +/* > + * Kexec is not supported in SEV-ES guests yet > + */ > +bool arch_kexec_supported(void) > +{ > + return !sev_es_active(); > +} _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization