On Wed, Apr 16, 2025, Vipin Sharma wrote:
> On 2025-04-16 11:24:37, Vipin Sharma wrote:
> > On 2025-04-01 08:57:13, Sean Christopherson wrote:
> > >
> > > + BUILD_BUG_ON(get_order(sizeof(struct kvm_svm) != 0));
> >
> > There is a typo here. It is checking sizeof(struct kvm_svm) != 0, instead
> > of checking get_order(...) != 0.
> >
> > > return 0;
> > >
> > > err_kvm_init:
> > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > > index b70ed72c1783..01264842bf45 100644
> > > --- a/arch/x86/kvm/vmx/vmx.c
> > > +++ b/arch/x86/kvm/vmx/vmx.c
> > > @@ -8755,6 +8755,7 @@ static int __init vmx_init(void)
> > > if (r)
> > > goto err_kvm_init;
> > >
> > > + BUILD_BUG_ON(get_order(sizeof(struct kvm_vmx) != 0));
> >
> > Same as above.
Ugh. That's what I get for violating the kernel's "don't check for '0'" rule
(I thought it would make the code more understandable). Bad me.
> After fixing the typo build is failing.
>
> Checked via pahole, sizes of struct have reduced but still not under 4k.
> After applying the patch:
>
> struct kvm{} - 4104
> struct kvm_svm{} - 4320
> struct kvm_vmx{} - 4128
>
> Also, this BUILD_BUG_ON() might not be reliable unless all of the ifdefs
> under kvm_[vmx|svm] and its children are enabled. Won't that be an
> issue?
That's what build bots (and to a lesser extent, maintainers) are for. An individual
developer might miss a particular config, but the build bots that run allyesconfig
will very quickly detect the issue, and then we fix it.
I also build what is effectively an "allkvmconfig" before officially applying
anything, so in general things like this shouldn't even make it to the bots.
