[xen staging] x86/shim: Simplify compat handling in write_start_info()

[patchbot@xxxxxxx]

commit ecf5db4003290f98f5b600adbbf36c185d3e7b21
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Apr 19 15:33:05 2021 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Apr 22 13:17:33 2021 +0100

    x86/shim: Simplify compat handling in write_start_info()
    
    Factor out a compat boolean to remove the lfence overhead from multiple
    is_pv_32bit_domain() calls.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/pv/shim.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index d16c0048c0..4c6f442274 100644
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -280,12 +280,12 @@ void __init pv_shim_setup_dom(struct domain *d, 
l4_pgentry_t *l4start,
 static void write_start_info(struct domain *d)
 {
     struct cpu_user_regs *regs = guest_cpu_user_regs();
-    start_info_t *si = map_domain_page(_mfn(is_pv_32bit_domain(d) ? regs->edx
-                                                                  : 
regs->rdx));
+    bool compat = is_pv_32bit_domain(d);
+    start_info_t *si = map_domain_page(_mfn(compat ? regs->edx : regs->rdx));
     uint64_t param;
 
     snprintf(si->magic, sizeof(si->magic), "xen-3.0-x86_%s",
-             is_pv_32bit_domain(d) ? "32p" : "64");
+             compat ? "32p" : "64");
     si->nr_pages = domain_tot_pages(d);
     si->shared_info = virt_to_maddr(d->shared_info);
     si->flags = 0;
@@ -300,7 +300,7 @@ static void write_start_info(struct domain *d)
                                           &si->console.domU.mfn) )
         BUG();
 
-    if ( is_pv_32bit_domain(d) )
+    if ( compat )
         xlat_start_info(si, XLAT_start_info_console_domU);
 
     unmap_domain_page(si);
--
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