Re: [PATCH v2 1/2] hw/riscv/virt.c: fix non-KVM --enable-debug build

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 31/8/23 10:42, Andrew Jones wrote:
> On Wed, Aug 30, 2023 at 10:35:02AM -0300, Daniel Henrique Barboza wrote:
>> A build with --enable-debug and without KVM will fail as follows:
>>
>> /usr/bin/ld: libqemu-riscv64-softmmu.fa.p/hw_riscv_virt.c.o: in function `virt_machine_init':
>> ./qemu/build/../hw/riscv/virt.c:1465: undefined reference to `kvm_riscv_aia_create'
>>
>> This happens because the code block with "if virt_use_kvm_aia(s)" isn't
>> being ignored by the debug build, resulting in an undefined reference to
>> a KVM only function.
>>
>> Add a 'kvm_enabled()' conditional together with virt_use_kvm_aia() will
>> make the compiler crop the kvm_riscv_aia_create() call entirely from a
>> non-KVM build. Note that adding the 'kvm_enabled()' conditional inside
>> virt_use_kvm_aia() won't fix the build because this function would need
>> to be inlined multiple times to make the compiler zero out the entire
>> block.
>>
>> While we're at it, use kvm_enabled() in all instances where
>> virt_use_kvm_aia() is checked to allow the compiler to elide these other
>> kvm-only instances as well.
>>
>> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
>> Fixes: dbdb99948e ("target/riscv: select KVM AIA in riscv virt machine")
>> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
>> ---
>>   hw/riscv/virt.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)


> I think I'd prefer
> 
>   /* We need this inlined for debug (-O0) builds */
>   static inline QEMU_ALWAYS_INLINE bool virt_use_kvm_aia(RISCVVirtState *s)
>   {
>      return kvm_enabled() && kvm_irqchip_in_kernel() && s->aia_type == VIRT_AIA_TYPE_APLIC_IMSIC;

Generally we should know whether KVM is enabled or not _before_
calling any foo_kvm() code, not after.

>   }