Re: [PATCH RESEND v2 03/17] KVM: X86: Don't track dirty for KVM_SET_[TSS_ADDR|IDENTITY_MAP_ADDR]

[Paolo Bonzini]

On 21/12/19 02:49, Peter Xu wrote:
> Originally, we have three code paths that can dirty a page without
> vcpu context for X86:
> 
>   - init_rmode_identity_map
>   - init_rmode_tss
>   - kvmgt_rw_gpa
> 
> init_rmode_identity_map and init_rmode_tss will be setup on
> destination VM no matter what (and the guest cannot even see them), so
> it does not make sense to track them at all.
> 
> To do this, a new parameter is added to kvm_[write|clear]_guest_page()
> to show whether we would like to track dirty bits for the operations.
> With that, pass in "false" to this new parameter for any guest memory
> write of the ioctls (KVM_SET_TSS_ADDR, KVM_SET_IDENTITY_MAP_ADDR).

We can also return the hva from x86_set_memory_region and
__x86_set_memory_region.

Paolo

> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
> ---
>  arch/x86/kvm/vmx/vmx.c   | 18 ++++++++++--------
>  include/linux/kvm_host.h |  5 +++--
>  virt/kvm/kvm_main.c      | 25 ++++++++++++++++---------
>  3 files changed, 29 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 04a8212704c1..1ff5a428f489 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -3452,24 +3452,24 @@ static int init_rmode_tss(struct kvm *kvm)
>  
>  	idx = srcu_read_lock(&kvm->srcu);
>  	fn = to_kvm_vmx(kvm)->tss_addr >> PAGE_SHIFT;
> -	r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE);
> +	r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE, false);
>  	if (r < 0)
>  		goto out;
>  	data = TSS_BASE_SIZE + TSS_REDIRECTION_SIZE;
>  	r = kvm_write_guest_page(kvm, fn++, &data,
> -			TSS_IOPB_BASE_OFFSET, sizeof(u16));
> +				 TSS_IOPB_BASE_OFFSET, sizeof(u16), false);
>  	if (r < 0)
>  		goto out;
> -	r = kvm_clear_guest_page(kvm, fn++, 0, PAGE_SIZE);
> +	r = kvm_clear_guest_page(kvm, fn++, 0, PAGE_SIZE, false);
>  	if (r < 0)
>  		goto out;
> -	r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE);
> +	r = kvm_clear_guest_page(kvm, fn, 0, PAGE_SIZE, false);
>  	if (r < 0)
>  		goto out;
>  	data = ~0;
>  	r = kvm_write_guest_page(kvm, fn, &data,
>  				 RMODE_TSS_SIZE - 2 * PAGE_SIZE - 1,
> -				 sizeof(u8));
> +				 sizeof(u8), false);
>  out:
>  	srcu_read_unlock(&kvm->srcu, idx);
>  	return r;
> @@ -3498,7 +3498,7 @@ static int init_rmode_identity_map(struct kvm *kvm)
>  		goto out2;
>  
>  	idx = srcu_read_lock(&kvm->srcu);
> -	r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
> +	r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE, false);
>  	if (r < 0)
>  		goto out;
>  	/* Set up identity-mapping pagetable for EPT in real mode */
> @@ -3506,7 +3506,8 @@ static int init_rmode_identity_map(struct kvm *kvm)
>  		tmp = (i << 22) + (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER |
>  			_PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE);
>  		r = kvm_write_guest_page(kvm, identity_map_pfn,
> -				&tmp, i * sizeof(tmp), sizeof(tmp));
> +					 &tmp, i * sizeof(tmp),
> +					 sizeof(tmp), false);
>  		if (r < 0)
>  			goto out;
>  	}
> @@ -7265,7 +7266,8 @@ static int vmx_write_pml_buffer(struct kvm_vcpu *vcpu)
>  		dst = vmcs12->pml_address + sizeof(u64) * vmcs12->guest_pml_index;
>  
>  		if (kvm_write_guest_page(vcpu->kvm, gpa_to_gfn(dst), &gpa,
> -					 offset_in_page(dst), sizeof(gpa)))
> +					 offset_in_page(dst), sizeof(gpa),
> +					 false))
>  			return 0;
>  
>  		vmcs12->guest_pml_index--;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 2ea1ea79befd..4e34cf97ca90 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -734,7 +734,7 @@ int kvm_read_guest(struct kvm *kvm, gpa_t gpa, void *data, unsigned long len);
>  int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>  			   void *data, unsigned long len);
>  int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
> -			 int offset, int len);
> +			 int offset, int len, bool track_dirty);
>  int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
>  		    unsigned long len);
>  int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
> @@ -744,7 +744,8 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>  				  unsigned long len);
>  int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>  			      gpa_t gpa, unsigned long len);
> -int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
> +int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len,
> +			 bool track_dirty);
>  int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
>  struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
>  bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 7ee28af9eb48..b1047173d78e 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2051,7 +2051,8 @@ int kvm_vcpu_read_guest_atomic(struct kvm_vcpu *vcpu, gpa_t gpa,
>  EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_atomic);
>  
>  static int __kvm_write_guest_page(struct kvm_memory_slot *memslot, gfn_t gfn,
> -			          const void *data, int offset, int len)
> +			          const void *data, int offset, int len,
> +				  bool track_dirty)
>  {
>  	int r;
>  	unsigned long addr;
> @@ -2062,16 +2063,19 @@ static int __kvm_write_guest_page(struct kvm_memory_slot *memslot, gfn_t gfn,
>  	r = __copy_to_user((void __user *)addr + offset, data, len);
>  	if (r)
>  		return -EFAULT;
> -	mark_page_dirty_in_slot(memslot, gfn);
> +	if (track_dirty)
> +		mark_page_dirty_in_slot(memslot, gfn);
>  	return 0;
>  }
>  
>  int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn,
> -			 const void *data, int offset, int len)
> +			 const void *data, int offset, int len,
> +			 bool track_dirty)
>  {
>  	struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
>  
> -	return __kvm_write_guest_page(slot, gfn, data, offset, len);
> +	return __kvm_write_guest_page(slot, gfn, data, offset, len,
> +				      track_dirty);
>  }
>  EXPORT_SYMBOL_GPL(kvm_write_guest_page);
>  
> @@ -2080,7 +2084,8 @@ int kvm_vcpu_write_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn,
>  {
>  	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
>  
> -	return __kvm_write_guest_page(slot, gfn, data, offset, len);
> +	return __kvm_write_guest_page(slot, gfn, data, offset,
> +				      len, true);
>  }
>  EXPORT_SYMBOL_GPL(kvm_vcpu_write_guest_page);
>  
> @@ -2093,7 +2098,7 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
>  	int ret;
>  
>  	while ((seg = next_segment(len, offset)) != 0) {
> -		ret = kvm_write_guest_page(kvm, gfn, data, offset, seg);
> +		ret = kvm_write_guest_page(kvm, gfn, data, offset, seg, true);
>  		if (ret < 0)
>  			return ret;
>  		offset = 0;
> @@ -2232,11 +2237,13 @@ int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>  }
>  EXPORT_SYMBOL_GPL(kvm_read_guest_cached);
>  
> -int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len)
> +int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len,
> +			 bool track_dirty)
>  {
>  	const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0)));
>  
> -	return kvm_write_guest_page(kvm, gfn, zero_page, offset, len);
> +	return kvm_write_guest_page(kvm, gfn, zero_page, offset, len,
> +				    track_dirty);
>  }
>  EXPORT_SYMBOL_GPL(kvm_clear_guest_page);
>  
> @@ -2248,7 +2255,7 @@ int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len)
>  	int ret;
>  
>  	while ((seg = next_segment(len, offset)) != 0) {
> -		ret = kvm_clear_guest_page(kvm, gfn, offset, seg);
> +		ret = kvm_clear_guest_page(kvm, gfn, offset, seg, true);
>  		if (ret < 0)
>  			return ret;
>  		offset = 0;
>