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

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Message-ID: <op.1rgo5llowjvjmi@hhuan26-mobl1.mshome.net>
Date:   Thu, 25 Aug 2022 09:57:11 -0500
From:   "Haitao Huang" <haitao.huang@...ux.intel.com>
To:     linux-sgx@...r.kernel.org, "Jarkko Sakkinen" <jarkko@...nel.org>
Cc:     "Paul Menzel" <pmenzel@...gen.mpg.de>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>,
        "Reinette Chatre" <reinette.chatre@...el.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] x86/sgx: Do not consider unsanitized pages an error

Hi Jarkko,

On Thu, 25 Aug 2022 03:08:02 -0500, Jarkko Sakkinen <jarkko@...nel.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@...gen.mpg.de>
> Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with  
> sgx_dirty_page_list")
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
>
> Cc: Haitao Huang <haitao.huang@...ux.intel.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Reinette Chatre <reinette.chatre@...el.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@...ux.intel.com>
Thanks
Haitao