On 08.08.2025 22:23, Andrew Cooper wrote: > ap_early_traps_init() will shortly be setting CR4.FRED. This requires that > cpu_info->cr4 is already set up, and that the enablement of CET doesn't > truncate FRED back out because of it's 32bit logic. > > For __high_start(), defer re-loading XEN_MINIMAL_CR4 until after %rsp is set > up and we can store the result in the cr4 field too. > > For s3_resume(), explicitly re-load XEN_MINIMAL_CR4. Later when loading all > features, use the mmu_cr4_features variable which is how the rest of Xen > performs this operation. > > No functional change, yet. > > Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
Reviewed-by: Jan Beulich <jbeul...@suse.com> > --- a/xen/arch/x86/acpi/wakeup_prot.S > +++ b/xen/arch/x86/acpi/wakeup_prot.S > @@ -63,6 +63,14 @@ LABEL(s3_resume) > pushq %rax > lretq > 1: > + > + GET_STACK_END(15) > + > + /* Enable minimal CR4 features. */ > + mov $XEN_MINIMAL_CR4, %eax > + mov %rax, STACK_CPUINFO_FIELD(cr4)(%r15) Strictly speaking this and ... > --- a/xen/arch/x86/boot/x86_64.S > +++ b/xen/arch/x86/boot/x86_64.S > @@ -11,16 +11,19 @@ ENTRY(__high_start) > mov %ecx,%gs > mov %ecx,%ss > > - /* Enable minimal CR4 features. */ > - mov $XEN_MINIMAL_CR4,%rcx > - mov %rcx,%cr4 > - > mov stack_start(%rip),%rsp > > /* Reset EFLAGS (subsumes CLI and CLD). */ > pushq $0 > popf > > + GET_STACK_END(15) > + > + /* Enable minimal CR4 features. */ > + mov $XEN_MINIMAL_CR4, %eax > + mov %rax, STACK_CPUINFO_FIELD(cr4)(%r15) ... this could be 32-bit stores, even in the longer run. Jan
