On Thu, Jan 26, 2023, Huang, Kai wrote:
> On Wed, 2023-01-25 at 17:22 +0000, Sean Christopherson wrote:
> > I agree that handling this in the common code would be cleaner, but repurposing
> > gfp_zero gets kludgy because it would require a magic value to say "don't initialize
> > the data", e.g. x86's mmu_shadowed_info_cache isn't pre-filled.
...
> > @@ -400,6 +405,13 @@ int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity,
> > if (WARN_ON_ONCE(!capacity))
> > return -EIO;
> >
> > + /*
> > + * Custom init values can be used only for page allocations,
> > + * and obviously conflict with __GFP_ZERO.
> > + */
> > + if (WARN_ON_ONCE(mc->init_value && (mc->kmem_cache || mc->gfp_zero)))
> > + return -EIO;
> > +
> > mc->objects = kvmalloc_array(sizeof(void *), capacity, gfp);
> > if (!mc->objects)
> > return -ENOMEM;
> >
> > base-commit: 503f0315c97739d3f8e645c500d81757dfbf76be
>
> init_value and gfp_zone is kinda redundant. How about removing gfp_zero
> completely?
>
> mmu_memory_cache_alloc_obj(...)
> {
> ...
> if (!mc->init_value)
> gfp_flags |= __GFP_ZERO;
> ...
> }
>
> And in kvm_mmu_create() you initialize all caches' init_value explicitly.
No, as mentioned above there's also a "don't initialize the data" case. Leaving
init_value=0 means those users would see unnecessary zeroing, and again I don't
want to use a magic value to say "don't initialize".
