[Xen-devel] [PATCH v2 2/9] x86/pv: Support do_set_segment_base() for compat guests

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

set_segment_base is the only hypercall exists in only one of the two modes
guests might run in; all other hypercalls are either implemented, or
unimplemented in both modes.

Remove this split, by allowing do_set_segment_base() to be called in the
compat hypercall path.  This change will simplify the verification logic in a
later change.

No behavioural change from a guests point of view.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Jan Beulich <JBeulich@xxxxxxxx>
---
 xen/arch/x86/x86_64/compat/entry.S | 2 +-
 xen/arch/x86/x86_64/mm.c           | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/x86_64/compat/entry.S 
b/xen/arch/x86/x86_64/compat/entry.S
index e80c53c..1b6a482 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -456,7 +456,7 @@ ENTRY(compat_hypercall_table)
         .quad compat_update_va_mapping_otherdomain
         .quad compat_iret
         .quad compat_vcpu_op
-        .quad compat_ni_hypercall       /* 25 */
+        .quad do_set_segment_base       /* 25 */
         .quad compat_mmuext_op
         .quad compat_xsm_op
         .quad compat_nmi_op
diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 7f858fb..250d3e0 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -1031,6 +1031,9 @@ long do_set_segment_base(unsigned int which, unsigned 
long base)
     struct vcpu *v = current;
     long ret = 0;
 
+    if ( is_pv_32bit_vcpu(v) )
+        return -ENOSYS; /* x86/64 only. */
+
     switch ( which )
     {
     case SEGBASE_FS:
-- 
2.1.4


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