diff mbox series

[v2] x86/shim: Simplify compat handling in write_start_info()

Message ID 20210420174118.2731-1-andrew.cooper3@citrix.com (mailing list archive)
State New, archived
Headers show
Series [v2] x86/shim: Simplify compat handling in write_start_info() | expand

Commit Message

Andrew Cooper April 20, 2021, 5:41 p.m. UTC 
Factor out a compat boolean to remove the lfence overhead from multiple
is_pv_32bit_domain() calls.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>

v2:
 * Reinstate the conditional for the start info pointer, in case Intel/AMD
   can't be persuaded to adjust the architectural guarentees for upper bits in
   compatibility mode transitions.
---
 xen/arch/x86/pv/shim.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Jan Beulich April 21, 2021, 9:29 a.m. UTC | #1 
On 20.04.2021 19:41, Andrew Cooper wrote:
> Factor out a compat boolean to remove the lfence overhead from multiple
> is_pv_32bit_domain() calls.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Roger Pau Monné <roger.pau@citrix.com>
> CC: Wei Liu <wl@xen.org>
> 
> v2:
>  * Reinstate the conditional for the start info pointer, in case Intel/AMD
>    can't be persuaded to adjust the architectural guarentees for upper bits in
>    compatibility mode transitions.

As indicated before, with this adjustment
Reviewed-by: Jan Beulich <jbeulich@suse.com>

Jan
diff mbox series

Patch

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);