Commit f4e4805e authored Jul 12, 2019 by Arnd Bergmann Committed by Paolo Bonzini Jul 15, 2019

x86: kvm: avoid -Wsometimes-uninitized warning



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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent 0b774629

arch/x86/kvm/hyperv.c

+9 −11

Original line number	Diff line number	Diff line
		@@ -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);

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