Re: [PATCH RFC v8 02/56] KVM: x86: Add 'update_mem_attr' x86 op

[Isaku Yamahata]

On Mon, Feb 20, 2023 at 12:37:53PM -0600,
Michael Roth <michael.roth@xxxxxxx> wrote:

> This callback will do any platform-specific handling needed for
> converting pages between shared/private.
> 
> Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> ---
>  arch/x86/include/asm/kvm-x86-ops.h |  1 +
>  arch/x86/include/asm/kvm_host.h    |  2 ++
>  arch/x86/kvm/mmu/mmu.c             | 13 +++++++++++++
>  include/linux/kvm_host.h           |  4 ++++
>  virt/kvm/kvm_main.c                | 29 +++++++++++++++++++++++++++++
>  5 files changed, 49 insertions(+)
> 
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 72183da010b8..a8aaf532c2ab 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -132,6 +132,7 @@ KVM_X86_OP(complete_emulated_msr)
>  KVM_X86_OP(vcpu_deliver_sipi_vector)
>  KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons);
>  KVM_X86_OP_OPTIONAL_RET0(fault_is_private);
> +KVM_X86_OP_OPTIONAL_RET0(update_mem_attr)
>  
>  #undef KVM_X86_OP
>  #undef KVM_X86_OP_OPTIONAL
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index f856d689dda0..2da3fb2d5d1b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1644,6 +1644,8 @@ struct kvm_x86_ops {
>  	void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
>  			     int root_level);
>  	bool (*fault_is_private)(struct kvm *kvm, gpa_t gpa, u64 error_code, bool *private_fault);
> +	int (*update_mem_attr)(struct kvm_memory_slot *slot, unsigned int attr,
> +			       gfn_t start, gfn_t end);
>  
>  	bool (*has_wbinvd_exit)(void);
>  
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index fb3f34b7391c..053bd77bbf52 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -7251,4 +7251,17 @@ void kvm_arch_set_memory_attributes(struct kvm *kvm,
>  		linfo_update_mixed(gfn, slot, level, mixed);
>  	}
>  }
> +
> +void kvm_arch_post_set_memory_attributes(struct kvm *kvm,
> +					 struct kvm_memory_slot *slot,
> +					 unsigned long attrs,
> +					 gfn_t start, gfn_t end)
> +{
> +	int ret;
> +
> +	ret = static_call(kvm_x86_update_mem_attr)(slot, attrs, start, end);
> +	if (ret)
> +		pr_warn_ratelimited("Failed to update GFN range 0x%llx-0x%llx with attributes 0x%lx. Ret: %d\n",
> +				    start, end, attrs, ret);
> +}
>  #endif
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index fdc59479b3e2..d200b8f45583 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -2330,6 +2330,10 @@ void kvm_arch_set_memory_attributes(struct kvm *kvm,
>  				    struct kvm_memory_slot *slot,
>  				    unsigned long attrs,
>  				    gfn_t start, gfn_t end);
> +void kvm_arch_post_set_memory_attributes(struct kvm *kvm,
> +					 struct kvm_memory_slot *slot,
> +					 unsigned long attrs,
> +					 gfn_t start, gfn_t end);
>  
>  static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
>  {
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index b68574ff6c30..8ec985f1c57d 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2561,6 +2561,32 @@ static void kvm_mem_attrs_changed(struct kvm *kvm, unsigned long attrs,
>  		kvm_flush_remote_tlbs(kvm);
>  }
>  
> +static void kvm_post_mem_attrs_changed(struct kvm *kvm, unsigned long attrs,
> +				       gfn_t start_orig, gfn_t end_orig)
> +{
> +	struct kvm_memory_slot *slot;
> +	struct kvm_memslots *slots;
> +	struct kvm_memslot_iter iter;
> +	int i;
> +
> +	for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
> +		slots = __kvm_memslots(kvm, i);
> +
> +		kvm_for_each_memslot_in_gfn_range(&iter, slots, start_orig, end_orig) {
> +			gfn_t start, end;
> +
> +			slot = iter.slot;
> +			start = max(start_orig, slot->base_gfn);
> +			end = min(end_orig, slot->base_gfn + slot->npages);
> +
> +			if (start >= end)
> +				continue;
> +
> +			kvm_arch_post_set_memory_attributes(kvm, slot, attrs, start, end);
> +		}
> +	}
> +}
> +
>  static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
>  					   struct kvm_memory_attributes *attrs)
>  {
> @@ -2602,6 +2628,9 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
>  	kvm_mmu_invalidate_end(kvm);
>  	KVM_MMU_UNLOCK(kvm);
>  
> +	if (i > start)
> +		kvm_post_mem_attrs_changed(kvm, attrs->attributes, start, i);
> +

Doesn't kvm_arch_set_memory_attributes() work for you? i.e the following patch.
The error check and pr_warn_ratelimited() can be pushed down into the callback.