lkml.org 
[lkml]   [2022]   [Oct]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v6 01/21] x86/tdx: Use enum to define page level of TDX supported page sizes
From
On 10/27/2022 7:16 AM, Kai Huang wrote:
> TDX supports 4K, 2M and 1G page sizes. When TDX guest accepts one page
> via try_accept_one(), it passes the page size level to the TDX module.
> Currently try_accept_one() uses hard-coded magic number for that.
>
> Introduce a new enum type to represent the page level of TDX supported
> page sizes to replace the hard-coded values. Both initializing the TDX
> module and KVM TDX support will need to use that too.
>
> Also, currently try_accept_one() uses an open-coded switch statement to
> get the TDX page level from the kernel page level. As KVM will also
> need to do the same thing, introduce a common helper to convert the
> kernel page level to the TDX page level.
>
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> ---
> arch/x86/coco/tdx/tdx.c | 20 ++++----------------
> arch/x86/include/asm/tdx.h | 33 +++++++++++++++++++++++++++++++++
> 2 files changed, 37 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 928dcf7a20d9..c5ff9647213d 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -655,7 +655,6 @@ static bool try_accept_one(phys_addr_t *start, unsigned long len,
> {
> unsigned long accept_size = page_level_size(pg_level);
> u64 tdcall_rcx;
> - u8 page_size;
>
> if (!IS_ALIGNED(*start, accept_size))
> return false;
> @@ -663,27 +662,16 @@ static bool try_accept_one(phys_addr_t *start, unsigned long len,
> if (len < accept_size)
> return false;
>
> + /* TDX only supports 4K/2M/1G page sizes */

yes, a page can be mapped as 1G size to TD via secure/shared EPT. But
for this particular TDX_ACCEPT_PAGE case, it only supports 4K and 2M
currently, which is defined in TDX module spec.

This also implies one thing can be improved in current kernel that
trying accepting a page from 1G in tdx_enc_status_changed() can be
optimized to from 2M. It can be changed to start from 1G when TDX
supports accepting 1G page directly.

> + if (pg_level < PG_LEVEL_4K || pg_level > PG_LEVEL_1G)
> + return false;
> /*
> * Pass the page physical address to the TDX module to accept the
> * pending, private page.
> *
> * Bits 2:0 of RCX encode page size: 0 - 4K, 1 - 2M, 2 - 1G.

Maybe the “page size” can be adjusted to “TDX page level” accordingly.

> */
> - switch (pg_level) {
> - case PG_LEVEL_4K:
> - page_size = 0;
> - break;
> - case PG_LEVEL_2M:
> - page_size = 1;
> - break;
> - case PG_LEVEL_1G:
> - page_size = 2;
> - break;
> - default:
> - return false;
> - }
> -
> - tdcall_rcx = *start | page_size;
> + tdcall_rcx = *start | to_tdx_pg_level(pg_level);
> if (__tdx_module_call(TDX_ACCEPT_PAGE, tdcall_rcx, 0, 0, 0, NULL))
> return false;
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index 020c81a7c729..1c166fb9c22f 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -20,6 +20,39 @@
>
> #ifndef __ASSEMBLY__
>
> +#include <asm/pgtable_types.h>
> +
> +/*
> + * The page levels of TDX supported page sizes (4K/2M/1G).
> + *
> + * Those values are part of the TDX module ABI. Do not change them.
> + */
> +enum tdx_pg_level {
> + TDX_PG_LEVEL_4K,
> + TDX_PG_LEVEL_2M,
> + TDX_PG_LEVEL_1G,
> + TDX_PG_LEVEL_NUM
> +};
> +
> +/*
> + * Get the TDX page level based on the kernel page level. The caller
> + * to make sure only pass 4K/2M/1G kernel page level.
> + */
> +static inline enum tdx_pg_level to_tdx_pg_level(enum pg_level pglvl)
> +{
> + switch (pglvl) {
> + case PG_LEVEL_4K:
> + return TDX_PG_LEVEL_4K;
> + case PG_LEVEL_2M:
> + return TDX_PG_LEVEL_2M;
> + case PG_LEVEL_1G:
> + return TDX_PG_LEVEL_1G;
> + default:
> + WARN_ON_ONCE(1);
> + }
> + return TDX_PG_LEVEL_NUM;
> +}
> +
> /*
> * Used to gather the output registers values of the TDCALL and SEAMCALL
> * instructions when requesting services from the TDX module.

\
 
 \ /
  Last update: 2022-10-27 09:10    [W:0.728 / U:0.452 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site