Re: [PATCH 3/6] KVM: Add a dedicated API for setting KVM-internal memslots

[Tao Su <tao1.su@linux.intel.com>]

On Fri, Aug 02, 2024 at 01:50:00PM -0700, Sean Christopherson wrote:
> Add a dedicated API for setting internal memslots, and have it explicitly
> disallow setting userspace memslots.  Setting a userspace memslots without
> a direct command from userspace would result in all manner of issues.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  arch/x86/kvm/x86.c       |  2 +-
>  include/linux/kvm_host.h |  4 ++--
>  virt/kvm/kvm_main.c      | 15 ++++++++++++---
>  3 files changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index af6c8cf6a37a..77949fee13f7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12794,7 +12794,7 @@ void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa,
>  		m.guest_phys_addr = gpa;
>  		m.userspace_addr = hva;
>  		m.memory_size = size;
> -		r = __kvm_set_memory_region(kvm, &m);
> +		r = kvm_set_internal_memslot(kvm, &m);
>  		if (r < 0)
>  			return ERR_PTR_USR(r);
>  	}
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index b341d00aae37..cefa274c0852 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1179,8 +1179,8 @@ enum kvm_mr_change {
>  	KVM_MR_FLAGS_ONLY,
>  };
>  
> -int __kvm_set_memory_region(struct kvm *kvm,
> -			    const struct kvm_userspace_memory_region2 *mem);
> +int kvm_set_internal_memslot(struct kvm *kvm,
> +			     const struct kvm_userspace_memory_region2 *mem);
>  void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);
>  void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen);
>  int kvm_arch_prepare_memory_region(struct kvm *kvm,
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index f202bdbfca9e..63b43644ed9f 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1973,8 +1973,8 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
>  	return false;
>  }
>  
> -int __kvm_set_memory_region(struct kvm *kvm,
> -			    const struct kvm_userspace_memory_region2 *mem)
> +static int __kvm_set_memory_region(struct kvm *kvm,
> +				   const struct kvm_userspace_memory_region2 *mem)
>  {
>  	struct kvm_memory_slot *old, *new;
>  	struct kvm_memslots *slots;
> @@ -2097,7 +2097,16 @@ int __kvm_set_memory_region(struct kvm *kvm,
>  	kfree(new);
>  	return r;
>  }
> -EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
> +
> +int kvm_set_internal_memslot(struct kvm *kvm,
> +			     const struct kvm_userspace_memory_region2 *mem)
> +{
> +	if (WARN_ON_ONCE(mem->slot < KVM_USER_MEM_SLOTS))
> +		return -EINVAL;
> +
> +	return  __kvm_set_memory_region(kvm, mem);
              ^^
Two spaces are introduced here.

> +}
> +EXPORT_SYMBOL_GPL(kvm_set_internal_memslot);
>  
>  static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
>  					  struct kvm_userspace_memory_region2 *mem)
> -- 
> 2.46.0.rc2.264.g509ed76dc8-goog
> 
>