Commit 9115bb12 authored Dec 10, 2018 by Peter Maydell Committed by Eduardo Habkost Dec 11, 2018

target/i386/kvm.c: Don't mark cpuid_data as QEMU_PACKED



clang complains about taking the address of a packed
member of a struct:

target/i386/kvm.c:1245:27: warning: taking address of packed member 'cpuid' of class or structure '' may result in an unaligned pointer value [-Waddress-of-packed-member]
    c = cpuid_find_entry(&cpuid_data.cpuid, 1, 0);
                          ^~~~~~~~~~~~~~~~
target/i386/kvm.c:1297:31: warning: taking address of packed member 'cpuid' of class or structure '' may result in an unaligned pointer value [-Waddress-of-packed-member]
        c = cpuid_find_entry(&cpuid_data.cpuid, kvm_base, 0);
                              ^~~~~~~~~~~~~~~~

The kernel's definitions of struct kvm_cpuid2 and struct
kvm_cpuid_entry2 are carefully set up with padding fields
so that there is no between-struct padding anyway, so
the QEMU_PACKED annotation is unnecessary and might result
in the compiler generating worse code. Drop it, and instead
assert at build time that there is no stray padding.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20181210114654.31433-1-peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

parent 1c65775f

target/i386/kvm.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -864,7 +864,15 @@ int kvm_arch_init_vcpu(CPUState *cs)
		struct {
		struct kvm_cpuid2 cpuid;
		struct kvm_cpuid_entry2 entries[KVM_MAX_CPUID_ENTRIES];
		} QEMU_PACKED cpuid_data;
		} cpuid_data;
		/*
		* The kernel defines these structs with padding fields so there
		* should be no extra padding in our cpuid_data struct.
		*/
		QEMU_BUILD_BUG_ON(sizeof(cpuid_data) !=
		sizeof(struct kvm_cpuid2) +
		sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES);

		X86CPU *cpu = X86_CPU(cs);
		CPUX86State *env = &cpu->env;
		uint32_t limit, i, j, cpuid_i;