linux-kernel - Re: [PATCH 2/6] KVM: Assert slots_lock is held in __kvm_set_memory

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Message-ID: <ZrFL0g97IGDTDdWS@google.com>
Date: Mon, 5 Aug 2024 15:01:54 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Tao Su <tao1.su@...ux.intel.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] KVM: Assert slots_lock is held in __kvm_set_memory_region()

On Mon, Aug 05, 2024, Tao Su wrote:
> On Fri, Aug 02, 2024 at 01:49:59PM -0700, Sean Christopherson wrote:
> > Add a proper lockdep assertion in __kvm_set_memory_region() instead of
> > relying on a function comment.  Opportunistically delete the entire
> > function comment as the API doesn't allocate memory or select a gfn,
> > and the "mostly for framebuffers" comment hasn't been true for a very long
> > time.
> > 
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > ---
> >  virt/kvm/kvm_main.c | 10 ++--------
> >  1 file changed, 2 insertions(+), 8 deletions(-)
> > 
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 0557d663b69b..f202bdbfca9e 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -1973,14 +1973,6 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
> >  	return false;
> >  }
> >  
> > -/*
> > - * Allocate some memory and give it an address in the guest physical address
> > - * space.
> > - *
> > - * Discontiguous memory is allowed, mostly for framebuffers.
> > - *
> > - * Must be called holding kvm->slots_lock for write.
> > - */
> >  int __kvm_set_memory_region(struct kvm *kvm,
> >  			    const struct kvm_userspace_memory_region2 *mem)
> >  {
> > @@ -1992,6 +1984,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
> >  	int as_id, id;
> >  	int r;
> >  
> > +	lockdep_assert_held(&kvm->slots_lock);
> 
> How about adding this lockdep assertion in __x86_set_memory_region() to replace
> this comment "/* Called with kvm->slots_lock held.  */" as well?

Ya, will do, I didn't see that comment.

Thanks!