Re: [PATCH qom-cpu 01/11] target-i386: Don't set any KVM flag by default if KVM is disabled

Gleb Natapov
2013-01-06T11:32:34Z

On Fri, Jan 04, 2013 at 08:01:02PM -0200, Eduardo Habkost wrote:
> This is a cleanup that tries to solve two small issues:
>
> - We don't need a separate kvm_pv_eoi_features variable just to keep a
> constant calculated at compile-time, and this style would require
> adding a separate variable (that's declared twice because of the
> CONFIG_KVM ifdef) for each feature that's going to be enabled/disable
> by machine-type compat code.
> - The pc-1.3 code is setting the kvm_pv_eoi flag on cpuid_kvm_features
> even when KVM is disabled at runtime. This small incosistency in
> the cpuid_kvm_features field isn't a problem today because
> cpuid_kvm_features is ignored by the TCG code, but it may cause
> unexpected problems later when refactoring the CPUID handling code.
>
> This patch eliminates the kvm_pv_eoi_features variable and simply uses
> CONFIG_KVM and kvm_enabled() inside the enable_kvm_pv_eoi() compat
> function, so it enables kvm_pv_eoi only if KVM is enabled. I believe
> this makes the behavior of enable_kvm_pv_eoi() clearer and easier to
> understand.
>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Cc: kvm@vger.kernel.org
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Gleb Natapov <gleb@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
>
> Changes v2:
> - Coding style fix
> ---
> target-i386/cpu.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 82685dc..e6435da 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -145,15 +145,17 @@ static uint32_t kvm_default_features = (1 << KVM_FEATURE_CLOCKSOURCE) |
> (1 << KVM_FEATURE_ASYNC_PF) |
> (1 << KVM_FEATURE_STEAL_TIME) |
> (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> -static const uint32_t kvm_pv_eoi_features = (0x1 << KVM_FEATURE_PV_EOI);
> #else
> static uint32_t kvm_default_features = 0;
> -static const uint32_t kvm_pv_eoi_features = 0;
> #endif
>
> void enable_kvm_pv_eoi(void)
> {
> - kvm_default_features |= kvm_pv_eoi_features;
> +#ifdef CONFIG_KVM
You do not need ifdef here.

> + if (kvm_enabled()) {
> + kvm_default_features |= (1UL << KVM_FEATURE_PV_EOI);
> + }
> +#endif
> }
>
> void host_cpuid(uint32_t function, uint32_t count,
> --
> 1.7.11.7

--
Gleb.