tboot_shutdown() calls into tboot to perform the actual system shutdown.
tboot isn't built with endbr annotations, and Xen has CET-IBT enabled on
newer hardware. shutdown_entry isn't annotated with endbr and Xen
faults:
Panic on CPU 0:
CONTROL-FLOW PROTECTION FAULT: #CP[0003] endbranch
And Xen hangs at this point.
Disabling CET-IBT let Xen and tboot power off, but reboot was
perfoming a poweroff instead of a warm reboot. Disabling all of CET,
i.e. shadow stacks as well, lets tboot reboot properly.
Fixes: cdbe2b0a1aec ("x86: Enable CET Indirect Branch Tracking")
Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
---
Without this fix, Xen subsequently hangs:
Reboot in five seconds...
[VT-D] IOMMU1: QI wait descriptor taking too long
IQA = 484897000
IQH = 0
IQT = 820
with no futher output.
---
xen/arch/x86/tboot.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/xen/arch/x86/tboot.c b/xen/arch/x86/tboot.c
index 90f6e805a9..86c4c22cac 100644
--- a/xen/arch/x86/tboot.c
+++ b/xen/arch/x86/tboot.c
@@ -353,6 +353,16 @@ void tboot_shutdown(uint32_t shutdown_type)
tboot_gen_xenheap_integrity(g_tboot_shared->s3_key, &xenheap_mac);
}
+ /*
+ * Disable CET - tboot may not be built with endbr, and it doesn't support
+ * shadow stacks.
+ */
+ if ( read_cr4() & X86_CR4_CET )
+ {
+ wrmsrl(MSR_S_CET, 0);
+ write_cr4(read_cr4() & ~X86_CR4_CET);
+ }
+
/*
* During early boot, we can be called by panic before idle_vcpu[0] is
* setup, but in that case we don't need to change page tables.
--
2.41.0
On 8/15/23 12:11, Jason Andryuk wrote: > tboot_shutdown() calls into tboot to perform the actual system shutdown. > tboot isn't built with endbr annotations, and Xen has CET-IBT enabled on > newer hardware. shutdown_entry isn't annotated with endbr and Xen > faults: > > Panic on CPU 0: > CONTROL-FLOW PROTECTION FAULT: #CP[0003] endbranch > > And Xen hangs at this point. > > Disabling CET-IBT let Xen and tboot power off, but reboot was > perfoming a poweroff instead of a warm reboot. Disabling all of CET, > i.e. shadow stacks as well, lets tboot reboot properly. > > Fixes: cdbe2b0a1aec ("x86: Enable CET Indirect Branch Tracking") > Signed-off-by: Jason Andryuk <jandryuk@gmail.com> > --- > Without this fix, Xen subsequently hangs: > > Reboot in five seconds... > [VT-D] IOMMU1: QI wait descriptor taking too long > IQA = 484897000 > IQH = 0 > IQT = 820 > > with no futher output. > --- > xen/arch/x86/tboot.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/xen/arch/x86/tboot.c b/xen/arch/x86/tboot.c > index 90f6e805a9..86c4c22cac 100644 > --- a/xen/arch/x86/tboot.c > +++ b/xen/arch/x86/tboot.c > @@ -353,6 +353,16 @@ void tboot_shutdown(uint32_t shutdown_type) > tboot_gen_xenheap_integrity(g_tboot_shared->s3_key, &xenheap_mac); > } > > + /* > + * Disable CET - tboot may not be built with endbr, and it doesn't support > + * shadow stacks. > + */ > + if ( read_cr4() & X86_CR4_CET ) > + { > + wrmsrl(MSR_S_CET, 0); > + write_cr4(read_cr4() & ~X86_CR4_CET); > + } > + > /* > * During early boot, we can be called by panic before idle_vcpu[0] is > * setup, but in that case we don't need to change page tables. Reviewed-by: Daniel P. Smith <dpsmith@apertussolutions.com>
On 15/08/2023 5:11 pm, Jason Andryuk wrote: > tboot_shutdown() calls into tboot to perform the actual system shutdown. > tboot isn't built with endbr annotations, and Xen has CET-IBT enabled on > newer hardware. shutdown_entry isn't annotated with endbr and Xen > faults: > > Panic on CPU 0: > CONTROL-FLOW PROTECTION FAULT: #CP[0003] endbranch > > And Xen hangs at this point. > > Disabling CET-IBT let Xen and tboot power off, but reboot was > perfoming a poweroff instead of a warm reboot. Disabling all of CET, > i.e. shadow stacks as well, lets tboot reboot properly. > > Fixes: cdbe2b0a1aec ("x86: Enable CET Indirect Branch Tracking") > Signed-off-by: Jason Andryuk <jandryuk@gmail.com> :sadpanda: I guess this is the least bad option going. Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
© 2016 - 2024 Red Hat, Inc.