lkml.org 
[lkml]   [2019]   [Jul]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] [v3] x86: kvm: avoid -Wsometimes-uninitized warning
Date
Clang notices a code path in which some variables are never
initialized, but fails to figure out that this can never happen
on i386 because is_64_bit_mode() always returns false.

arch/x86/kvm/hyperv.c:1610:6: error: variable 'ingpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
if (!longmode) {
^~~~~~~~~
arch/x86/kvm/hyperv.c:1632:55: note: uninitialized use occurs here
trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
^~~~~
arch/x86/kvm/hyperv.c:1610:2: note: remove the 'if' if its condition is always true
if (!longmode) {
^~~~~~~~~~~~~~~
arch/x86/kvm/hyperv.c:1595:18: note: initialize the variable 'ingpa' to silence this warning
u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
^
= 0
arch/x86/kvm/hyperv.c:1610:6: error: variable 'outgpa' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
arch/x86/kvm/hyperv.c:1610:6: error: variable 'param' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]

Flip the condition around to avoid the conditional execution on i386.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v3: reword commit log, simplify patch again
v2: make the change inside of is_64_bit_mode().
---
arch/x86/kvm/hyperv.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index a39e38f13029..c10a8b10b203 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1594,7 +1594,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
{
u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
uint16_t code, rep_idx, rep_cnt;
- bool fast, longmode, rep;
+ bool fast, rep;

/*
* hypercall generates UD from non zero cpl and real mode
@@ -1605,9 +1605,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
return 1;
}

- longmode = is_64_bit_mode(vcpu);
-
- if (!longmode) {
+#ifdef CONFIG_X86_64
+ if (is_64_bit_mode(vcpu)) {
+ param = kvm_rcx_read(vcpu);
+ ingpa = kvm_rdx_read(vcpu);
+ outgpa = kvm_r8_read(vcpu);
+ } else
+#endif
+ {
param = ((u64)kvm_rdx_read(vcpu) << 32) |
(kvm_rax_read(vcpu) & 0xffffffff);
ingpa = ((u64)kvm_rbx_read(vcpu) << 32) |
@@ -1615,13 +1620,6 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
outgpa = ((u64)kvm_rdi_read(vcpu) << 32) |
(kvm_rsi_read(vcpu) & 0xffffffff);
}
-#ifdef CONFIG_X86_64
- else {
- param = kvm_rcx_read(vcpu);
- ingpa = kvm_rdx_read(vcpu);
- outgpa = kvm_r8_read(vcpu);
- }
-#endif

code = param & 0xffff;
fast = !!(param & HV_HYPERCALL_FAST_BIT);
--
2.20.0
\
 
 \ /
  Last update: 2019-07-12 16:15    [W:0.039 / U:5.148 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site