On Mon, Mar 17, 2025, Vipin Sharma wrote:
> On 2025-03-14 19:40:08, Sean Christopherson wrote:
> > Dynamically allocate the (massive) array of hashed lists used to track
> > shadow pages, as the array itself is 32KiB, i.e. is an order-3 allocation
> > all on its own, and is *exactly* an order-3 allocation. Dynamically
> > allocating the array will allow allocating "struct kvm" using regular
> > kmalloc(), and will also allow deferring allocation of the array until
> > it's actually needed, i.e. until the first shadow root is allocated.
> >
> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > ---
> > arch/x86/include/asm/kvm_host.h | 4 ++--
> > arch/x86/kvm/mmu/mmu.c | 21 ++++++++++++++++++++-
> > arch/x86/kvm/x86.c | 5 ++++-
> > 3 files changed, 26 insertions(+), 4 deletions(-)
> >
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -6673,13 +6685,19 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
> > kvm_tdp_mmu_zap_invalidated_roots(kvm, true);
> > }
> >
> > -void kvm_mmu_init_vm(struct kvm *kvm)
> > +int kvm_mmu_init_vm(struct kvm *kvm)
> > {
> > + int r;
> > +
> > kvm->arch.shadow_mmio_value = shadow_mmio_value;
> > INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
> > INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages);
> > spin_lock_init(&kvm->arch.mmu_unsync_pages_lock);
> >
> > + r = kvm_mmu_alloc_page_hash(kvm);
> > + if (r)
> > + return r;
> > +
>
> In the patch 3, shouldn't this be moved to else part of the below
> 'if (tdp_mmu_enabled)' line? Otherwise, this hash array will always get
> allocated.
Ugh, I botched the rebase, and didn't point test that the allocations actually
went away.
Before commit 0df9dab891ff ("KVM: x86/mmu: Stop zapping invalidated TDP MMU roots
asynchronously"), kvm_mmu_init_tdp_mmu() returned a value and so the code was:
if (tdp_mmu_enabled)
r = kvm_mmu_init_tdp_mmu(kvm);
else
r = kvm_mmu_alloc_page_hash(kvm);
if (r < 0)
return r;
I suppose the least ugly approach is:
if (tdp_mmu_enabled) {
kvm_mmu_init_tdp_mmu(kvm);
} else {
r = kvm_mmu_alloc_page_hash(kvm);
if (r)
return r;
}
> > if (tdp_mmu_enabled)
> > kvm_mmu_init_tdp_mmu(kvm);
> >
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -12704,7 +12704,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> > if (ret)
> > goto out;
> >
> > - kvm_mmu_init_vm(kvm);
> > + ret = kvm_mmu_init_vm(kvm);
> > + if (ret)
> > + goto out_cleanup_page_track;
> >
> > ret = kvm_x86_call(vm_init)(kvm);
> > if (ret)
> > @@ -12757,6 +12759,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> >
> > out_uninit_mmu:
> > kvm_mmu_uninit_vm(kvm);
> > +out_cleanup_page_track:
>
> I think there is a memory leak in this series.
/facepalm
Good job, me.
Thanks for the review!
