[XEN][PATCH v2 3/4] x86: hvm: factor out COMPAT code under ifdefs

[Grygorii Strashko <grygorii_strashko@epam.com>]

From: Grygorii Strashko <grygorii_strashko@epam.com>

Factor out COMPAT HVM code under ifdefs in preparation for making HVM
COMPAT code optional.

- hypercall-defs.c updated to always provide compat declaration for:
physdev_op, grant_table_op, grant_table_op. This reduces number of COMPAT
ifdefs in HVM code and lets compiler DCE do the job.

- Only 64-bit shinfo is supported with COMPAT=n, so struct
arch_domain->has_32bit_shinfo field is moved under COMPAT ifdef and
has_32bit_shinfo() is updated to account for COMPAT=n.

Signed-off-by: Grygorii Strashko <grygorii_strashko@epam.com>
---
changes in v2:
- update hypercall-defs.c to always provide compat declaration for:
  physdev_op, grant_table_op, grant_table_op
- move struct arch_domain->has_32bit_shinfo is moved under COMPAT ifdef
- return hvm_hypercall()
- use ASSERT_UNREACHABLE() in hvm_do_multicall_call()
- constify has_32bit_shinfo() for COMPAT=n

 xen/arch/x86/hvm/hvm.c            | 16 ++++++++++++++++
 xen/arch/x86/hvm/hypercall.c      | 13 +++++++++++++
 xen/arch/x86/include/asm/domain.h |  9 +++++++--
 xen/include/hypercall-defs.c      |  9 +++++++--
 4 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 0fd3f95b6e0e..19524cb7a914 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -69,7 +69,9 @@
 #include <public/version.h>
 #include <public/vm_event.h>
 
+#ifdef CONFIG_COMPAT
 #include <compat/hvm/hvm_op.h>
+#endif
 
 bool __read_mostly hvm_enabled;
 
@@ -1255,6 +1257,7 @@ static int cf_check hvm_save_cpu_xsave_states(
     return 0;
 }
 
+#ifdef CONFIG_COMPAT
 /*
  * Structure layout conformity checks, documenting correctness of the cast in
  * the invocation of validate_xstate() below.
@@ -1267,6 +1270,7 @@ CHECK_FIELD_(struct, xsave_hdr, xcomp_bv);
 CHECK_FIELD_(struct, xsave_hdr, reserved);
 #undef compat_xsave_hdr
 #undef xen_xsave_hdr
+#endif /* CONFIG_COMPAT */
 
 static int cf_check hvm_load_cpu_xsave_states(
     struct domain *d, hvm_domain_context_t *h)
@@ -3991,8 +3995,14 @@ static void hvm_latch_shinfo_size(struct domain *d)
      */
     if ( current->domain == d )
     {
+#ifdef CONFIG_COMPAT
+        /*
+         * Only 64-bit shinfo is supported when COMPAT 32-bit hypercalls
+         * interface is disabled
+         */
         d->arch.has_32bit_shinfo =
             hvm_guest_x86_mode(current) != X86_MODE_64BIT;
+#endif
 
         /*
          * Make sure that the timebase in the shared info structure is correct.
@@ -4965,6 +4975,7 @@ static int do_altp2m_op(
 #endif /* CONFIG_ALTP2M */
 }
 
+#ifdef CONFIG_COMPAT
 DEFINE_XEN_GUEST_HANDLE(compat_hvm_altp2m_op_t);
 
 /*
@@ -4992,10 +5003,12 @@ DEFINE_XEN_GUEST_HANDLE(compat_hvm_altp2m_op_t);
 
 CHECK_hvm_altp2m_op;
 CHECK_hvm_altp2m_set_mem_access_multi;
+#endif /* CONFIG_COMPAT */
 
 static int compat_altp2m_op(
     XEN_GUEST_HANDLE_PARAM(void) arg)
 {
+#ifdef CONFIG_COMPAT
     int rc = 0;
     struct compat_hvm_altp2m_op a;
     union
@@ -5063,6 +5076,9 @@ static int compat_altp2m_op(
     }
 
     return rc;
+#else
+    return -EOPNOTSUPP;
+#endif /* CONFIG_COMPAT */
 }
 
 static int hvmop_get_mem_type(
diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 52cae1d15312..1ee0193b69af 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -170,6 +170,7 @@ int hvm_hypercall(struct cpu_user_regs *regs)
         HVM_DBG_LOG(DBG_LEVEL_HCALL, "hcall%lu(%x, %x, %x, %x, %x)", eax,
                     regs->ebx, regs->ecx, regs->edx, regs->esi, regs->edi);
 
+#ifdef CONFIG_COMPAT
         curr->hcall_compat = true;
         call_handlers_hvm32(eax, regs->eax, regs->ebx, regs->ecx, regs->edx,
                             regs->esi, regs->edi);
@@ -177,6 +178,9 @@ int hvm_hypercall(struct cpu_user_regs *regs)
 
         if ( !curr->hcall_preempted && regs->eax != -ENOSYS )
             clobber_regs(regs, eax, hvm, 32);
+#else
+        regs->eax = -ENOSYS;
+#endif
     }
 
     hvmemul_cache_restore(curr, token);
@@ -207,10 +211,19 @@ enum mc_disposition hvm_do_multicall_call(struct mc_state *state)
     }
     else
     {
+#ifdef CONFIG_COMPAT
         struct compat_multicall_entry *call = &state->compat_call;
 
         call_handlers_hvm32(call->op, call->result, call->args[0], call->args[1],
                             call->args[2], call->args[3], call->args[4]);
+#else
+        /*
+         * code should never reach here in case !CONFIG_COMPAT as any
+         * 32-bit hypercall should bail out earlier from hvm_hypercall()
+         * with -EOPNOTSUPP
+         */
+        ASSERT_UNREACHABLE();
+#endif
     }
 
     return !hvm_get_cpl(curr) ? mc_continue : mc_preempt;
diff --git a/xen/arch/x86/include/asm/domain.h b/xen/arch/x86/include/asm/domain.h
index 5df8c7825333..0005f4450931 100644
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -12,8 +12,11 @@
 #include <public/vcpu.h>
 #include <public/hvm/hvm_info_table.h>
 
-#define has_32bit_shinfo(d)    ((d)->arch.has_32bit_shinfo)
-
+#ifdef CONFIG_COMPAT
+#define has_32bit_shinfo(d) ((d)->arch.has_32bit_shinfo)
+#else
+#define has_32bit_shinfo(d) ((void)(d), false)
+#endif
 /*
  * Set to true if either the global vector-type callback or per-vCPU
  * LAPIC vectors are used. Assume all vCPUs will use
@@ -365,8 +368,10 @@ struct arch_domain
     /* NB. protected by d->event_lock and by irq_desc[irq].lock */
     struct radix_tree_root irq_pirq;
 
+#ifdef CONFIG_COMPAT
     /* Is shared-info page in 32-bit format? */
     bool has_32bit_shinfo;
+#endif
 
     /* Is PHYSDEVOP_eoi to automatically unmask the event channel? */
     bool auto_unmask;
diff --git a/xen/include/hypercall-defs.c b/xen/include/hypercall-defs.c
index cef08eeec1b8..08c01153ac56 100644
--- a/xen/include/hypercall-defs.c
+++ b/xen/include/hypercall-defs.c
@@ -80,6 +80,8 @@ rettype: compat int
 #define PREFIX_compat
 #endif
 
+#define PREFIX_compat_always compat
+
 #ifdef CONFIG_ARM
 #define PREFIX_dep dep
 #define PREFIX_do_arm do_arm
@@ -104,10 +106,10 @@ defhandle: trap_info_compat_t
 defhandle: physdev_op_compat_t
 #endif
 
-prefix: do PREFIX_hvm PREFIX_compat PREFIX_do_arm
+prefix: do PREFIX_hvm PREFIX_compat_always PREFIX_do_arm
 physdev_op(int cmd, void *arg)
 
-prefix: do PREFIX_hvm PREFIX_compat
+prefix: do PREFIX_hvm PREFIX_compat_always
 #if defined(CONFIG_GRANT_TABLE) || defined(CONFIG_PV_SHIM)
 grant_table_op(unsigned int cmd, void *uop, unsigned int count)
 #endif
@@ -156,6 +158,9 @@ platform_op(compat_platform_op_t *u_xenpf_op)
 #ifdef CONFIG_KEXEC
 kexec_op(unsigned int op, void *uarg)
 #endif
+#else /* CONFIG_COMPAT */
+prefix: PREFIX_compat_always
+memory_op(unsigned int cmd, void *arg)
 #endif /* CONFIG_COMPAT */
 
 #if defined(CONFIG_PV) || defined(CONFIG_ARM)
-- 
2.34.1