Re: [PATCH] arm64: fix documentation on kernel pages mappings to HYP VA

Yury Norov
2017-09-26T18:46:00Z

Ping?

On Wed, Sep 13, 2017 at 09:08:30PM +0300, Yury Norov wrote:
> The Documentation/arm64/memory.txt says:
> When using KVM, the hypervisor maps kernel pages in EL2, at a fixed
> offset from the kernel VA (top 24bits of the kernel VA set to zero):
>
> In fact, kernel addresses are transleted to HYP with kern_hyp_va macro,
> which has more options, and none of them assumes clearing of top 24bits
> of the kernel VA.
>
> Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
> ---
> Documentation/arm64/memory.txt | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt
> index d7273a5f6456..c39895d7e3a2 100644
> --- a/Documentation/arm64/memory.txt
> +++ b/Documentation/arm64/memory.txt
> @@ -86,9 +86,12 @@ Translation table lookup with 64KB pages:
> +-------------------------------------------------> [63] TTBR0/1
>
>
> -When using KVM, the hypervisor maps kernel pages in EL2, at a fixed
> -offset from the kernel VA (top 24bits of the kernel VA set to zero):
> -
> -Start End Size Use
> ------------------------------------------------------------------------
> -0000004000000000 0000007fffffffff 256GB kernel objects mapped in HYP
> +When using KVM without Virtualization Host Extensions, the hypervisor maps
> +kernel pages in EL2, at a fixed offset from the kernel VA. Namely, top 16
> +or 25 bits of the kernel VA set to zero depending on ARM64_VA_BITS_48 or
> +ARM64_VA_BITS_39 config option selected; or top 17 or 26 bits of the kernel
> +VA set to zero if CPU has Reduced HYP mapping offset capability. See
> +kern_hyp_va macro.
> +
> +When using KVM with Virtualization Host Extensions, no additional mappings
> +created as host kernel already operates in EL2.
> --
> 2.11.0