[PATCH] x86: Fix build with the get/set_reg() infrastructure

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

I clearly messed up concluding that the stubs were safe to drop.

The is_{pv,hvm}_domain() predicates are not symmetrical with both CONFIG_PV
and CONFIG_HVM.  As a result logic of the form `if ( pv/hvm ) ... else ...`
will always have one side which can't be DCE'd.

While technically only the hvm stubs are needed, due to the use of the
is_pv_domain() predicate in guest_{rd,wr}msr(), sort out the pv stubs too to
avoid leaving a bear trap for future users.

Fixes: 88d3ff7ab15d ("x86/guest: Introduce {get,set}_reg() infrastructure")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
---
 xen/arch/x86/include/asm/hvm/hvm.h   |  9 +++++++++
 xen/arch/x86/include/asm/pv/domain.h | 17 +++++++++++++----
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/include/asm/hvm/hvm.h 
b/xen/arch/x86/include/asm/hvm/hvm.h
index 842f98763c4b..76170c129c35 100644
--- a/xen/arch/x86/include/asm/hvm/hvm.h
+++ b/xen/arch/x86/include/asm/hvm/hvm.h
@@ -854,6 +854,15 @@ static inline int hvm_vmtrace_get_option(
     return -EOPNOTSUPP;
 }
 
+static inline uint64_t hvm_get_reg(struct vcpu *v, unsigned int reg)
+{
+    ASSERT_UNREACHABLE();
+}
+static inline void hvm_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
+{
+    ASSERT_UNREACHABLE();
+}
+
 #define is_viridian_domain(d) ((void)(d), false)
 #define is_viridian_vcpu(v) ((void)(v), false)
 #define has_viridian_time_ref_count(d) ((void)(d), false)
diff --git a/xen/arch/x86/include/asm/pv/domain.h 
b/xen/arch/x86/include/asm/pv/domain.h
index 3a67816764c9..4ef4660a01ac 100644
--- a/xen/arch/x86/include/asm/pv/domain.h
+++ b/xen/arch/x86/include/asm/pv/domain.h
@@ -65,10 +65,6 @@ static inline unsigned long get_pcid_bits(const struct vcpu 
*v, bool is_xpti)
 #endif
 }
 
-/* See hvm_{get,set}_reg() for description. */
-uint64_t pv_get_reg(struct vcpu *v, unsigned int reg);
-void pv_set_reg(struct vcpu *v, unsigned int reg, uint64_t val);
-
 #ifdef CONFIG_PV
 
 void pv_vcpu_destroy(struct vcpu *v);
@@ -93,6 +89,10 @@ unsigned long pv_fixup_guest_cr4(const struct vcpu *v, 
unsigned long cr4);
 /* Create a cr4 value to load into hardware, based on vcpu settings. */
 unsigned long pv_make_cr4(const struct vcpu *v);
 
+/* See hvm_{get,set}_reg() for description. */
+uint64_t pv_get_reg(struct vcpu *v, unsigned int reg);
+void pv_set_reg(struct vcpu *v, unsigned int reg, uint64_t val);
+
 bool xpti_pcid_enabled(void);
 
 #else  /* !CONFIG_PV */
@@ -106,6 +106,15 @@ static inline int pv_domain_initialise(struct domain *d) { 
return -EOPNOTSUPP; }
 
 static inline unsigned long pv_make_cr4(const struct vcpu *v) { return ~0ul; }
 
+static inline uint64_t pv_get_reg(struct vcpu *v, unsigned int reg)
+{
+    ASSERT_UNREACHABLE();
+}
+static inline void pv_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
+{
+    ASSERT_UNREACHABLE();
+}
+
 #endif /* CONFIG_PV */
 
 void paravirt_ctxt_switch_from(struct vcpu *v);
-- 
2.11.0