On Tue, May 11, 2021 at 10:56 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Tue, May 11, 2021, Ben Gardon wrote:
> > Small refactor to facilitate allocating rmaps for all memslots at once.
> >
> > No functional change expected.
> >
> > Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/x86.c | 39 ++++++++++++++++++++++++++++++---------
> > 1 file changed, 30 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 1e1f4f31e586..cc0440b5b35d 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -10911,10 +10911,35 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
> > kvm_page_track_free_memslot(slot);
> > }
> >
> > +static int memslot_rmap_alloc(struct kvm_memory_slot *slot,
> > + unsigned long npages)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < KVM_NR_PAGE_SIZES; ++i) {
> > + int lpages;
> > + int level = i + 1;
> > +
> > + lpages = gfn_to_index(slot->base_gfn + npages - 1,
> > + slot->base_gfn, level) + 1;
>
> Might as well assign lpages at its declaration, i.e.
>
> int lpages = gfn_to_index(slot->base_gfn + npages - 1,
> slot->base_gfn, level) + 1;
I'll do this if I end up sending out a v5.
> > +
> > + slot->arch.rmap[i] =
> > + kvcalloc(lpages, sizeof(*slot->arch.rmap[i]),
> > + GFP_KERNEL_ACCOUNT);
>
> Eh, I don't think avoiding a 3 char overrun is worth splitting across three lines.
> E.g. this is perfectly readable
>
> slot->arch.rmap[i] = kvcalloc(lpages, sizeof(*slot->arch.rmap[i]),
> GFP_KERNEL_ACCOUNT);
>
> Alternatively, the rmap size could be captured in a local var, e.g.
>
> const int sz = sizeof(*slot->arch.rmap[0]);
>
> ...
>
> slot->arch.rmap[i] = kvcalloc(lpages, sz, GFP_KERNEL_ACCOUNT);
I like this suggestion. Much nicer. Will incorporate if I send a v5.
> if (!slot->arch.rmap[i]) {
> memslot_rmap_free(slot);
> return -ENOMEM;
> }
>
> > + if (!slot->arch.rmap[i]) {
> > + memslot_rmap_free(slot);
> > + return -ENOMEM;
>
> Reaaaally getting into nitpicks, what do you think about changing this to a goto
> with the error handling at the bottom? Obviously not necessary by any means,
> but for me it makes it easier to see that all rmaps are freed on failure. My
> eyes skipped over that on the first read through. E.g.
>
> if (!slot_arch.rmap[i])
> goto err;
> }
>
> return 0;
>
> err:
> memslot_rmap_free(slot);
> return -ENOMEM;
>
Lol, I had a goto in v3, but David Hildenbrand suggested removing it
and putting the free in the loop. I think I like it more this way too.
>
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
> > unsigned long npages)
> > {
> > int i;
> > + int r;
>
> Personal preference, for short declarations like this I like putting 'em on a
> single line.
>
> > /*
> > * Clear out the previous array pointers for the KVM_MR_MOVE case. The
> > @@ -10923,7 +10948,11 @@ static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
> > */
> > memset(&slot->arch, 0, sizeof(slot->arch));
> >
> > - for (i = 0; i < KVM_NR_PAGE_SIZES; ++i) {
> > + r = memslot_rmap_alloc(slot, npages);
> > + if (r)
> > + return r;
> > +
> > + for (i = 1; i < KVM_NR_PAGE_SIZES; ++i) {
> > struct kvm_lpage_info *linfo;
> > unsigned long ugfn;
> > int lpages;
> > @@ -10932,14 +10961,6 @@ static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
> > lpages = gfn_to_index(slot->base_gfn + npages - 1,
> > slot->base_gfn, level) + 1;
> >
> > - slot->arch.rmap[i] =
> > - kvcalloc(lpages, sizeof(*slot->arch.rmap[i]),
> > - GFP_KERNEL_ACCOUNT);
> > - if (!slot->arch.rmap[i])
> > - goto out_free;
> > - if (i == 0)
> > - continue;
> > -
> > linfo = kvcalloc(lpages, sizeof(*linfo), GFP_KERNEL_ACCOUNT);
> > if (!linfo)
> > goto out_free;
> > --
> > 2.31.1.607.g51e8a6a459-goog
> >
