[xen staging] x86/domctl: Reorder user_regs accesses for efficiency

[patchbot@xxxxxxx]

commit 50e7b8a32dcb1360dbe9e0fa8b81a3ad02d0b670
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Jul 20 10:12:13 2026 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Mon Jul 20 12:05:36 2026 +0100

    x86/domctl: Reorder user_regs accesses for efficiency
    
    The current order is derived from expanding XLAT_cpu_user_regs() which used
    the x86_32 cpu_user_regs order.  This is correct for one the blocks, but not
    the others.
    
    In order to work with the prefetcher, rather than against it, loads want to 
be
    in field order.  Make this so for the three paths reading an x86_64
    cpu_user_regs.
    
    No functional change.
    
    Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
    Reviewed-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
---
 xen/arch/x86/domain.c |  6 +++---
 xen/arch/x86/domctl.c | 10 +++++-----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 53a86ba373..996b50af7a 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1259,17 +1259,17 @@ int arch_set_info_guest(
         v->arch.user_regs.r14               = c.nat->user_regs.r14;
         v->arch.user_regs.r13               = c.nat->user_regs.r13;
         v->arch.user_regs.r12               = c.nat->user_regs.r12;
+        v->arch.user_regs.rbp               = c.nat->user_regs.rbp;
+        v->arch.user_regs.rbx               = c.nat->user_regs.rbx;
         v->arch.user_regs.r11               = c.nat->user_regs.r11;
         v->arch.user_regs.r10               = c.nat->user_regs.r10;
         v->arch.user_regs.r9                = c.nat->user_regs.r9;
         v->arch.user_regs.r8                = c.nat->user_regs.r8;
-        v->arch.user_regs.rbx               = c.nat->user_regs.rbx;
+        v->arch.user_regs.rax               = c.nat->user_regs.rax;
         v->arch.user_regs.rcx               = c.nat->user_regs.rcx;
         v->arch.user_regs.rdx               = c.nat->user_regs.rdx;
         v->arch.user_regs.rsi               = c.nat->user_regs.rsi;
         v->arch.user_regs.rdi               = c.nat->user_regs.rdi;
-        v->arch.user_regs.rbp               = c.nat->user_regs.rbp;
-        v->arch.user_regs.rax               = c.nat->user_regs.rax;
         v->arch.user_regs.rip               = c.nat->user_regs.rip;
         v->arch.user_regs.cs                = c.nat->user_regs.cs;
         v->arch.user_regs.rflags            = (c.nat->user_regs.rflags & 
X86_EFLAGS_ALL) | X86_EFLAGS_MBS;
diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 3ea4c650ee..2ecd81d89b 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -1485,17 +1485,17 @@ void arch_get_info_guest(struct vcpu *v, 
vcpu_guest_context_u c)
         c.nat->user_regs.r14               = v->arch.user_regs.r14;
         c.nat->user_regs.r13               = v->arch.user_regs.r13;
         c.nat->user_regs.r12               = v->arch.user_regs.r12;
+        c.nat->user_regs.rbp               = v->arch.user_regs.rbp;
+        c.nat->user_regs.rbx               = v->arch.user_regs.rbx;
         c.nat->user_regs.r11               = v->arch.user_regs.r11;
         c.nat->user_regs.r10               = v->arch.user_regs.r10;
         c.nat->user_regs.r9                = v->arch.user_regs.r9;
         c.nat->user_regs.r8                = v->arch.user_regs.r8;
-        c.nat->user_regs.rbx               = v->arch.user_regs.rbx;
+        c.nat->user_regs.rax               = v->arch.user_regs.rax;
         c.nat->user_regs.rcx               = v->arch.user_regs.rcx;
         c.nat->user_regs.rdx               = v->arch.user_regs.rdx;
         c.nat->user_regs.rsi               = v->arch.user_regs.rsi;
         c.nat->user_regs.rdi               = v->arch.user_regs.rdi;
-        c.nat->user_regs.rbp               = v->arch.user_regs.rbp;
-        c.nat->user_regs.rax               = v->arch.user_regs.rax;
         c.nat->user_regs.rip               = v->arch.user_regs.rip;
         c.nat->user_regs.cs                = v->arch.user_regs.cs;
         c.nat->user_regs.rflags            = v->arch.user_regs.rflags;
@@ -1514,13 +1514,13 @@ void arch_get_info_guest(struct vcpu *v, 
vcpu_guest_context_u c)
     else
     {
         /* Backing memory is pre-zeroed. */
+        c.cmp->user_regs.ebp               = v->arch.user_regs.ebp;
         c.cmp->user_regs.ebx               = v->arch.user_regs.ebx;
+        c.cmp->user_regs.eax               = v->arch.user_regs.eax;
         c.cmp->user_regs.ecx               = v->arch.user_regs.ecx;
         c.cmp->user_regs.edx               = v->arch.user_regs.edx;
         c.cmp->user_regs.esi               = v->arch.user_regs.esi;
         c.cmp->user_regs.edi               = v->arch.user_regs.edi;
-        c.cmp->user_regs.ebp               = v->arch.user_regs.ebp;
-        c.cmp->user_regs.eax               = v->arch.user_regs.eax;
         c.cmp->user_regs.eip               = v->arch.user_regs.eip;
         c.cmp->user_regs.cs                = v->arch.user_regs.cs;
         c.cmp->user_regs.eflags            = v->arch.user_regs.eflags;
--
generated by git-patchbot for /home/xen/git/xen.git#staging