On Thu, Jan 26, 2023 at 10:01:41PM +0000,
Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> 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".
The abuses of gfp_flags as zeroing doesn't work for Secure-EPT page table.
It doesn't need zeroing without initial value. So I used the patch as is.
--
Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
