[v1] TDX MMU Part 2

[PATCH 03/21] KVM: x86/mmu: Do not enable page track for TD guest

Posted by Rick Edgecombe 1 year, 3 months ago

From: Yan Zhao <yan.y.zhao@intel.com>

TDX does not support write protection and hence page track.
Though !tdp_enabled and kvm_shadow_root_allocated(kvm) are always false
for TD guest, should also return false when external write tracking is
enabled.

Cc: Yuan Yao <yuan.yao@linux.intel.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
---
v19:
- drop TDX: from the short log
- Added reviewed-by: BinBin
---
 arch/x86/kvm/mmu/page_track.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index 561c331fd6ec..26436113103a 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -35,6 +35,9 @@ static bool kvm_external_write_tracking_enabled(struct kvm *kvm)
 
 bool kvm_page_track_write_tracking_enabled(struct kvm *kvm)
 {
+	if (kvm->arch.vm_type == KVM_X86_TDX_VM)
+		return false;
+
 	return kvm_external_write_tracking_enabled(kvm) ||
 	       kvm_shadow_root_allocated(kvm) || !tdp_enabled;
 }
-- 
2.34.1

Re: [PATCH 03/21] KVM: x86/mmu: Do not enable page track for TD guest

Posted by Paolo Bonzini 1 year, 3 months ago

On 9/4/24 05:07, Rick Edgecombe wrote:
> From: Yan Zhao <yan.y.zhao@intel.com>
> 
> TDX does not support write protection and hence page track.
> Though !tdp_enabled and kvm_shadow_root_allocated(kvm) are always false
> for TD guest, should also return false when external write tracking is
> enabled.
> 
> Cc: Yuan Yao <yuan.yao@linux.intel.com>
> Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
> ---
> v19:
> - drop TDX: from the short log
> - Added reviewed-by: BinBin
> ---
>   arch/x86/kvm/mmu/page_track.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
> index 561c331fd6ec..26436113103a 100644
> --- a/arch/x86/kvm/mmu/page_track.c
> +++ b/arch/x86/kvm/mmu/page_track.c
> @@ -35,6 +35,9 @@ static bool kvm_external_write_tracking_enabled(struct kvm *kvm)
>   
>   bool kvm_page_track_write_tracking_enabled(struct kvm *kvm)
>   {
> +	if (kvm->arch.vm_type == KVM_X86_TDX_VM)
> +		return false;
> +
>   	return kvm_external_write_tracking_enabled(kvm) ||
>   	       kvm_shadow_root_allocated(kvm) || !tdp_enabled;
>   }

You should instead return an error from 
kvm_enable_external_write_tracking().

This will cause kvm_page_track_register_notifier() and therefore 
intel_vgpu_open_device() to fail.

Paolo

Re: [PATCH 03/21] KVM: x86/mmu: Do not enable page track for TD guest

Posted by Edgecombe, Rick P 1 year, 3 months ago

On Mon, 2024-09-09 at 15:53 +0200, Paolo Bonzini wrote:
> 
> You should instead return an error from 
> kvm_enable_external_write_tracking().
> 
> This will cause kvm_page_track_register_notifier() and therefore 
> intel_vgpu_open_device() to fail.

Makes sense, thanks.