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From: Roger Pau Monne <roger.pau@citrix.com>
To: <xen-devel@lists.xenproject.org>
Cc: Roger Pau Monne <roger.pau@citrix.com>,
	Jan Beulich <jbeulich@suse.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>, Wei Liu <wl@xen.org>
Subject: [PATCH 2/2] x86/pv: fix clang build without CONFIG_PV32
Date: Fri, 23 Apr 2021 11:43:43 +0200	[thread overview]
Message-ID: <20210423094343.5850-3-roger.pau@citrix.com> (raw)
In-Reply-To: <20210423094343.5850-1-roger.pau@citrix.com>

Clang reports the following build error without CONFIG_PV:

hypercall.c:253:10: error: variable 'op' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
    if ( !is_pv_32bit_vcpu(curr) )
         ^~~~~~~~~~~~~~~~~~~~~~~
hypercall.c:282:21: note: uninitialized use occurs here
    return unlikely(op == __HYPERVISOR_iret)
                    ^~
/root/src/xen/xen/include/xen/compiler.h:21:43: note: expanded from macro 'unlikely'
#define unlikely(x)   __builtin_expect(!!(x),0)
                                          ^
hypercall.c:253:5: note: remove the 'if' if its condition is always true
    if ( !is_pv_32bit_vcpu(curr) )
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
hypercall.c:251:21: note: initialize the variable 'op' to silence this warning
    unsigned long op;
                    ^
                     = 0

Rearrange the code in arch_do_multicall_call so that the if guards the
32bit branch and when CONFIG_PV32 is not set there's no conditional at
all.

Fixes: 527922008bc ('x86: slim down hypercall handling when !PV32')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Should the is_pv_32bit_vcpu be wrapped in an unlikely hint?
---
 xen/arch/x86/pv/hypercall.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
index e30c59b6286..d573f74aa1e 100644
--- a/xen/arch/x86/pv/hypercall.c
+++ b/xen/arch/x86/pv/hypercall.c
@@ -250,34 +250,34 @@ enum mc_disposition arch_do_multicall_call(struct mc_state *state)
     struct vcpu *curr = current;
     unsigned long op;
 
-    if ( !is_pv_32bit_vcpu(curr) )
+#ifdef CONFIG_PV32
+    if ( is_pv_32bit_vcpu(curr) )
     {
-        struct multicall_entry *call = &state->call;
+        struct compat_multicall_entry *call = &state->compat_call;
 
         op = call->op;
         if ( (op < ARRAY_SIZE(pv_hypercall_table)) &&
-             pv_hypercall_table[op].native )
-            call->result = pv_hypercall_table[op].native(
+             pv_hypercall_table[op].compat )
+            call->result = pv_hypercall_table[op].compat(
                 call->args[0], call->args[1], call->args[2],
                 call->args[3], call->args[4], call->args[5]);
         else
             call->result = -ENOSYS;
     }
-#ifdef CONFIG_PV32
     else
+#endif
     {
-        struct compat_multicall_entry *call = &state->compat_call;
+        struct multicall_entry *call = &state->call;
 
         op = call->op;
         if ( (op < ARRAY_SIZE(pv_hypercall_table)) &&
-             pv_hypercall_table[op].compat )
-            call->result = pv_hypercall_table[op].compat(
+             pv_hypercall_table[op].native )
+            call->result = pv_hypercall_table[op].native(
                 call->args[0], call->args[1], call->args[2],
                 call->args[3], call->args[4], call->args[5]);
         else
             call->result = -ENOSYS;
     }
-#endif
 
     return unlikely(op == __HYPERVISOR_iret)
            ? mc_exit
-- 
2.30.1



  parent reply	other threads:[~2021-04-23  9:44 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-23  9:43 [PATCH 0/2] x86/clang: build fixes Roger Pau Monne
2021-04-23  9:43 ` [PATCH 1/2] x86/oprofile: fix oprofile for clang build Roger Pau Monne
2021-04-23  9:45   ` Jan Beulich
2021-04-23  9:43 ` Roger Pau Monne [this message]
2021-04-23  9:46   ` [PATCH 2/2] x86/pv: fix clang build without CONFIG_PV32 Roger Pau Monné
2021-04-23  9:48   ` Jan Beulich

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