On Mon, May 16, 2022, David Matlack wrote:
> -int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min)
> +static int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity, int min)
I still find it somewhat kludgy to have callers provide an capacity. It's not
terrible while there's only a single call site, but if a use case comes along
for using an oversized cache with multiple call sites, it'll be gross.
Tweaking my idea of a "custom" wrapper, what about adding an "oversized" wrapper?
That yields clear, firm rules on when to use each helper, guards against calling
the "standard" flavor with an impossible @min, and addresses Mingwei's concern
that a misguided user could specify a nonsensically small capacity.
The only quirk is that kvm_mmu_topup_memory_cache_oversized() has a fixed min,
but IMO that's an acceptable tradeoff, and it's a non-issue until another user
pops up.
static int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc,
int capacity, int min)
{
gfp_t gfp = GFP_KERNEL_ACCOUNT;
void *obj;
if (mc->nobjs >= min)
return 0;
if (unlikely(!mc->objects)) {
capacity = max(min, KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE);
mc->objects = kvmalloc_array(sizeof(void *), capacity, gfp);
if (!mc->objects)
return -ENOMEM;
mc->capacity = capacity;
}
/* It is illegal to request a different capacity across topups. */
if (WARN_ON_ONCE(mc->capacity != capacity))
return -EIO;
while (mc->nobjs < mc->capacity) {
obj = mmu_memory_cache_alloc_obj(mc, gfp);
if (!obj)
return mc->nobjs >= min ? 0 : -ENOMEM;
mc->objects[mc->nobjs++] = obj;
}
return 0;
}
int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min)
{
const int capacity = KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE;
if (WARN_ON_ONCE(min > capacity))
min = capacity;
return __kvm_mmu_topup_memory_cache(mc, capacity, min);
}
/* Oversized caches have a fixed size, i.e. min == capacity == size. */
int kvm_mmu_topup_memory_cache_oversized(struct kvm_mmu_memory_cache *mc, int size)
{
if (WARN_ON_ONCE(size < KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE)
size = KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE;
return __kvm_mmu_topup_memory_cache(mc, size, size);
}
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