Re: [PATCH 2/2] x86/kexec/64: Forbid kexec when running as an SEV-ES guest
From: Eric W. Biederman <hidden>
Date: 2021-05-06 17:42:26
Also in:
kexec, kvm, lkml, stable, virtualization
Joerg Roedel [off-list ref] writes:
From: Joerg Roedel <redacted> 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
quoted hunk
Cc: stable@vger.kernel.org # v5.10+ Signed-off-by: Joerg Roedel <redacted> --- 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(); +}