Re: [PATCH v3] x86/sgx: Do not consider unsanitized pages an error

Haitao Huang
2022-08-25T14:57:19Z

Hi Jarkko,

On Thu, 25 Aug 2022 03:08:02 -0500, Jarkko Sakkinen <jarkko@kernel.org>
wrote:

> If sgx_dirty_page_list ends up being non-empty, currently this triggers
> WARN_ON(), which produces a lot of noise, and can potentially crash the
> kernel, depending on the kernel command line.
>
> However, if the SGX subsystem initialization is retracted, the
> sanitization
> process could end up in the middle, and sgx_dirty_page_list be left
> non-empty for legit reasons.
>
> Replace this faulty behavior with more verbose version
> __sgx_sanitize_pages(), which can optionally print EREMOVE error code and
> the number of unsanitized pages.
>
> Link:
> https://lore.kernel.org/linux-sgx/20220825051827.246698-1-jarkko@kernel.org/T/#u
> Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
> Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with
> sgx_dirty_page_list")
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
>
> Cc: Haitao Huang <haitao.huang@linux.intel.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Reinette Chatre <reinette.chatre@intel.com>
> ---
> v3:
> - Remove WARN_ON().
> - Tuned comments and the commit message a bit.
>
> v2:
> - Replaced WARN_ON() with optional pr_info() inside
> __sgx_sanitize_pages().
> - Rewrote the commit message.
> - Added the fixes tag.
> ---
> arch/x86/kernel/cpu/sgx/main.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c
> b/arch/x86/kernel/cpu/sgx/main.c
> index 515e2a5f25bb..d204520a5e26 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -50,16 +50,17 @@ static LIST_HEAD(sgx_dirty_page_list);
> * from the input list, and made available for the page allocator. SECS
> pages
> * prepending their children in the input list are left intact.
> */
> -static void __sgx_sanitize_pages(struct list_head *dirty_page_list)
> +static void __sgx_sanitize_pages(struct list_head *dirty_page_list,
> bool verbose)
> {
> struct sgx_epc_page *page;
> + int dirty_count = 0;
> LIST_HEAD(dirty);
> int ret;
> /* dirty_page_list is thread-local, no need for a lock: */

Just a nitpick,
Although it is not added in this patch, the above comment is not accurate.
The list is accessed one thread only: filled first in main thread, then
only ever accessed here.

IIUC, could you remove or update that comment?

Other than that, FWIW:
Reviewed-by: Haitao Huang <haitao.huang@linux.intel.com>
Thanks
Haitao