Re: [PATCH 2/6] KVM: arm64: Use 0b11 for encoding PKVM_NOPAGE
From: Marc Zyngier
Date: Fri Mar 14 2025 - 07:07:09 EST
On Thu, 27 Feb 2025 00:33:06 +0000,
Quentin Perret <qperret@xxxxxxxxxx> wrote:
>
> The page ownership state encoded as 0b11 is currently considered
> reserved for future use, and PKVM_NOPAGE uses bit 2. In order to
> simplify the relocation of the hyp ownership state into the
> vmemmap in later patches, let's use the 'reserved' encoding for
> the PKVM_NOPAGE state. The struct hyp_page layout isn't guaranteed
> stable at all, so there is no real reason to have 'reserved' encodings.
>
> No functional changes intended.
>
> Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx>
> ---
> arch/arm64/kvm/hyp/include/nvhe/memory.h | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h
> index 34233d586060..642b5e05fe77 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h
> @@ -13,18 +13,15 @@
> * 01: The page is owned by the page-table owner, but is shared
> * with another entity.
> * 10: The page is shared with, but not owned by the page-table owner.
> - * 11: Reserved for future use (lending).
> */
> enum pkvm_page_state {
> PKVM_PAGE_OWNED = 0ULL,
> PKVM_PAGE_SHARED_OWNED = BIT(0),
> PKVM_PAGE_SHARED_BORROWED = BIT(1),
> - __PKVM_PAGE_RESERVED = BIT(0) | BIT(1),
>
> /* Meta-states which aren't encoded directly in the PTE's SW bits */
> - PKVM_NOPAGE = BIT(2),
> + PKVM_NOPAGE = BIT(0) | BIT(1),
Isn't this comment stale now?
M.
--
Without deviation from the norm, progress is not possible.