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

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Message-ID: <ZrCQSXmbBK5XZqd8@linux.bj.intel.com>
Date: Mon, 5 Aug 2024 16:41:45 +0800
From: Tao Su <tao1.su@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.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 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?

> +
>  	r = check_memory_region_flags(kvm, mem);
>  	if (r)
>  		return r;
> -- 
> 2.46.0.rc2.264.g509ed76dc8-goog
> 
>