Re: [libvirt] [PATCH qom-cpu 2/7] target-i386: Don't set any KVM flag by default if KVM is disabled
On Wed, Jan 09, 2013 at 10:46:12AM +0100, Igor Mammedov wrote:
On Mon, 7 Jan 2013 16:20:43 -0200
Eduardo Habkost <ehabkost(a)redhat.com> 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
> 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.
Subj doesn't match what patch actually does.
Have you meant "Don't set kvm_pv_eoi flag by default if KVM is disabled"?
Although "eliminate kvm_pv_eoi_features variable" might better describe what
patch is doing.
True. The other flags in kvm_default_features may be already set and
will be copied to cpuid_kvm_features even if kvm_enabled() is false.
I had a previous version of this patch that also changed the code using
kvm_default_features to check kvm_enabled(), but I removed that part and
kept only the kvm_pv_eoi_features variable removal.
Andreas, please ignore this patch (it is not necessary anymore as this
series doesn't include machine-type compatibility code for kvm_mmu).
Patches 2-7 don't depend on this patch and should apply cleanly without
it.
I will send a new version later, probably with a separate patch to
ignore kvm_default_features if kvm_enabled() is false (so there's no
need to even check kvm_enabled() inside enable_kvm_pv_eoi()).
>
> Signed-off-by: Eduardo Habkost <ehabkost(a)redhat.com>
> ---
> Cc: kvm(a)vger.kernel.org
> Cc: Michael S. Tsirkin <mst(a)redhat.com>
> Cc: Gleb Natapov <gleb(a)redhat.com>
> Cc: Marcelo Tosatti <mtosatti(a)redhat.com>
>
> Changes v2:
> - Coding style fix
>
> Changes v3:
> - Eliminate #ifdef by using the fake KVM_FEATURE_PV_EOI #define
> ---
> target-i386/cpu.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 951e206..40400ac 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -164,15 +164,15 @@ 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;
> + if (kvm_enabled()) {
> + kvm_default_features |= (1UL << KVM_FEATURE_PV_EOI);
> + }
> }
>
> void host_cpuid(uint32_t function, uint32_t count,
--
Eduardo