[xen master] x86/boot: Adjust CR4 handling around percpu_early_traps_init()

[patchbot@xxxxxxx]

commit 8218f8cf452bfa701d18d61d8a8e0f3a61f511de
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon May 26 15:32:44 2025 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Aug 28 23:12:32 2025 +0100

    x86/boot: Adjust CR4 handling around percpu_early_traps_init()
    
    percpu_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 X86_CR4_FRED back out because of using 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.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/acpi/wakeup_prot.S | 18 ++++++++++++++----
 xen/arch/x86/boot/x86_64.S      | 15 ++++++++++-----
 2 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/acpi/wakeup_prot.S b/xen/arch/x86/acpi/wakeup_prot.S
index cc40fddc38..0f02ea7b4b 100644
--- 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, sync cached state. */
+        mov     $XEN_MINIMAL_CR4, %eax
+        mov     %rax, STACK_CPUINFO_FIELD(cr4)(%r15)
+        mov     %rax, %cr4
+
         /* Set up early exceptions and CET before entering C properly. */
         call    percpu_early_traps_init
 
@@ -77,7 +85,9 @@ LABEL(s3_resume)
         wrmsr
 
         /* Enable CR4.CET. */
-        mov     $XEN_MINIMAL_CR4 | X86_CR4_CET, %ecx
+        mov     $X86_CR4_CET, %ecx
+        or      STACK_CPUINFO_FIELD(cr4)(%r15), %rcx
+        mov     %rcx, STACK_CPUINFO_FIELD(cr4)(%r15)
         mov     %rcx, %cr4
 
         /* WARNING! call/ret now fatal (iff SHSTK) until SETSSBSY loads SSP */
@@ -120,9 +130,9 @@ LABEL(s3_resume)
 .L_cet_done:
 #endif /* CONFIG_XEN_SHSTK || CONFIG_XEN_IBT */
 
-        /* Restore CR4 from the cpuinfo block. */
-        GET_STACK_END(bx)
-        mov     STACK_CPUINFO_FIELD(cr4)(%rbx), %rax
+        /* Load all CR4 settings. */
+        mov     mmu_cr4_features(%rip), %rax
+        mov     %rax, STACK_CPUINFO_FIELD(cr4)(%r15)
         mov     %rax, %cr4
 
         call    mtrr_bp_restore
diff --git a/xen/arch/x86/boot/x86_64.S b/xen/arch/x86/boot/x86_64.S
index d0e7449a14..3a5ad27644 100644
--- 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, sync cached state. */
+        mov     $XEN_MINIMAL_CR4, %eax
+        mov     %rax, STACK_CPUINFO_FIELD(cr4)(%r15)
+        mov     %rax, %cr4
+
         /* Reload code selector. */
         pushq   $__HYPERVISOR_CS
         leaq    1f(%rip),%rax
@@ -45,7 +48,9 @@ ENTRY(__high_start)
         wrmsr
 
         /* Enable CR4.CET. */
-        mov     $XEN_MINIMAL_CR4 | X86_CR4_CET, %ecx
+        mov     $X86_CR4_CET, %ecx
+        or      STACK_CPUINFO_FIELD(cr4)(%r15), %rcx
+        mov     %rcx, STACK_CPUINFO_FIELD(cr4)(%r15)
         mov     %rcx, %cr4
 
         /* WARNING! call/ret now fatal (iff SHSTK) until SETSSBSY loads SSP */
--
generated by git-patchbot for /home/xen/git/xen.git#master