2023-06-18 00:12:09

by Mingwei Zhang

Subject: [PATCH 4/6] KVM: Documentation: Add the missing tdp_mmu_root_count into kvm_mmu_page

Add tdp_mmu_root_count into kvm_mmu_page description. tdp_mmu_root_count is
an atomic counter used only in TDP MMU. Its usage and meaning is slightly
different with root_counter in shadow MMU. Update the doc.

Signed-off-by: Mingwei Zhang <[email protected]>
---
Documentation/virt/kvm/x86/mmu.rst | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/Documentation/virt/kvm/x86/mmu.rst b/Documentation/virt/kvm/x86/mmu.rst
index 36bfe0fe02bb..3dce2426ad6d 100644
--- a/Documentation/virt/kvm/x86/mmu.rst
+++ b/Documentation/virt/kvm/x86/mmu.rst
@@ -230,6 +230,12 @@ Shadow pages contain the following information:
A counter keeping track of how many hardware registers (guest cr3 or
pdptrs) are now pointing at the page. While this counter is nonzero, the
page cannot be destroyed. See role.invalid.
+ tdp_mmu_root_count:
+ An atomic reference counter in TDP MMU that allows for parallel
+ accesses. Accessing the page requires lifting the counter value. The
+ initial value is set as 2 indicating one reference from vCPU and one
+ from TDP MMU itself. While this counter is nonzero, the page cannot be
+ destroyed. Note this field is a union with root_count.
parent_ptes:
The reverse mapping for the pte/ptes pointing at this page's spt. If
parent_ptes bit 0 is zero, only one spte points at this page and
--
2.41.0.162.gfafddb0af9-goog

2023-06-22 08:52:55

by Huang, Kai

Subject: Re: [PATCH 4/6] KVM: Documentation: Add the missing tdp_mmu_root_count into kvm_mmu_page

On Sun, 2023-06-18 at 00:08 +0000, Mingwei Zhang wrote:
> Add tdp_mmu_root_count into kvm_mmu_page description. tdp_mmu_root_count is
> an atomic counter used only in TDP MMU. Its usage and meaning is slightly
> different with root_counter in shadow MMU. Update the doc.
>
> Signed-off-by: Mingwei Zhang <[email protected]>
> ---
> Documentation/virt/kvm/x86/mmu.rst | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/virt/kvm/x86/mmu.rst b/Documentation/virt/kvm/x86/mmu.rst
> index 36bfe0fe02bb..3dce2426ad6d 100644
> --- a/Documentation/virt/kvm/x86/mmu.rst
> +++ b/Documentation/virt/kvm/x86/mmu.rst
> @@ -230,6 +230,12 @@ Shadow pages contain the following information:
> A counter keeping track of how many hardware registers (guest cr3 or
> pdptrs) are now pointing at the page. While this counter is nonzero, the
> page cannot be destroyed. See role.invalid.
> + tdp_mmu_root_count:
> + An atomic reference counter in TDP MMU that allows for parallel
^
Please explicitly say "TDP MMU root page" ?

> + accesses. Accessing the page requires lifting the counter value. The
> + initial value is set as 2 indicating one reference from vCPU and one
^
to ?

> + from TDP MMU itself. 
>


> While this counter is nonzero, the page cannot be
> + destroyed. 
>

I guess this sentence is implied by "reference counter" mentioned in the first
sentence.

> Note this field is a union with root_count.
>

2023-06-26 18:12:28

by Mingwei Zhang

Subject: Re: [PATCH 4/6] KVM: Documentation: Add the missing tdp_mmu_root_count into kvm_mmu_page

On Thu, Jun 22, 2023, Huang, Kai wrote:
> On Sun, 2023-06-18 at 00:08 +0000, Mingwei Zhang wrote:
> > Add tdp_mmu_root_count into kvm_mmu_page description. tdp_mmu_root_count is
> > an atomic counter used only in TDP MMU. Its usage and meaning is slightly
> > different with root_counter in shadow MMU. Update the doc.
> >
> > Signed-off-by: Mingwei Zhang <[email protected]>
> > ---
> > Documentation/virt/kvm/x86/mmu.rst | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/virt/kvm/x86/mmu.rst b/Documentation/virt/kvm/x86/mmu.rst
> > index 36bfe0fe02bb..3dce2426ad6d 100644
> > --- a/Documentation/virt/kvm/x86/mmu.rst
> > +++ b/Documentation/virt/kvm/x86/mmu.rst
> > @@ -230,6 +230,12 @@ Shadow pages contain the following information:
> > A counter keeping track of how many hardware registers (guest cr3 or
> > pdptrs) are now pointing at the page. While this counter is nonzero, the
> > page cannot be destroyed. See role.invalid.
> > + tdp_mmu_root_count:
> > + An atomic reference counter in TDP MMU that allows for parallel
> ^
> Please explicitly say "TDP MMU root page" ?
>
> > + accesses. Accessing the page requires lifting the counter value. The
> > + initial value is set as 2 indicating one reference from vCPU and one
> ^
> to ?
>
> > + from TDP MMU itself.?
> >
>
>
> > While this counter is nonzero, the page cannot be
> > + destroyed.?
> >
>
> I guess this sentence is implied by "reference counter" mentioned in the first
> sentence.
>

Will make the changes in next version.

-Mingwei