Messages in this thread | | | Date | Tue, 26 Oct 2021 18:14:34 +0200 | Subject | Re: [PATCH MANUALSEL 5.14 1/5] KVM: X86: fix lazy allocation of rmaps | From | Paolo Bonzini <> |
| |
On 25/10/21 22:38, Sasha Levin wrote: > From: Paolo Bonzini <pbonzini@redhat.com> > > [ Upstream commit fa13843d1565d4c5b3aeb9be3343b313416bef46 ] > > If allocation of rmaps fails, but some of the pointers have already been written, > those pointers can be cleaned up when the memslot is freed, or even reused later > for another attempt at allocating the rmaps. Therefore there is no need to > WARN, as done for example in memslot_rmap_alloc, but the allocation *must* be > skipped lest KVM will overwrite the previous pointer and will indeed leak memory. > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Sasha Levin <sashal@kernel.org> > --- > arch/x86/kvm/x86.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 4b0e866e9f08..60d9aa0ab389 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -11341,7 +11341,8 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot, > int lpages = gfn_to_index(slot->base_gfn + npages - 1, > slot->base_gfn, level) + 1; > > - WARN_ON(slot->arch.rmap[i]); > + if (slot->arch.rmap[i]) > + continue; > > slot->arch.rmap[i] = kvcalloc(lpages, sz, GFP_KERNEL_ACCOUNT); > if (!slot->arch.rmap[i]) { >
NACK
There is no lazy allocation of rmaps in 5.14, and any failure to allocate goes straight to memslot_rmap_free followed by return -ENOMEM. So the WARN_ON is justified there.
Paolo
| |