Re: [PATCH v10 1/3] KVM: Implement dirty quota-based throttling of vcpus

[Sean Christopherson <seanjc@google.com>]

On Wed, Feb 21, 2024, Shivam Kumar wrote:
> @@ -1291,6 +1293,13 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
>  bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn);
>  bool kvm_vcpu_is_visible_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
>  unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn);
> +#ifdef CONFIG_HAVE_KVM_DIRTY_QUOTA
> +void update_dirty_quota(struct kvm *kvm, unsigned long page_size_bytes);
> +#else
> +static inline void update_dirty_quota(struct kvm *kvm, unsigned long page_size_bytes)
> +{
> +}
> +#endif
>  void mark_page_dirty_in_slot(struct kvm *kvm, const struct kvm_memory_slot *memslot, gfn_t gfn);
>  void mark_page_dirty(struct kvm *kvm, gfn_t gfn);
>  
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index c3308536482b..217f19100003 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -210,6 +210,7 @@ struct kvm_xen_exit {
>  #define KVM_EXIT_NOTIFY           37
>  #define KVM_EXIT_LOONGARCH_IOCSR  38
>  #define KVM_EXIT_MEMORY_FAULT     39
> +#define KVM_EXIT_DIRTY_QUOTA_EXHAUSTED 40
>  
>  /* For KVM_EXIT_INTERNAL_ERROR */
>  /* Emulate instruction failed. */
> @@ -491,6 +492,12 @@ struct kvm_run {
>  		struct kvm_sync_regs regs;
>  		char padding[SYNC_REGS_SIZE_BYTES];
>  	} s;
> +	/*
> +	 * Number of bytes the vCPU is allowed to dirty if KVM_CAP_DIRTY_QUOTA is
> +	 * enabled. KVM_RUN exits with KVM_EXIT_DIRTY_QUOTA_EXHAUSTED if this quota
> +	 * is exhausted, i.e. dirty_quota_bytes <= 0.
> +	 */
> +	long dirty_quota_bytes;

This needs to be a u64 so that the size is consistent for 32-bit and 64-bit
userspace vs. kernel.