linux-kernel - Re: [PATCH] x86/sgx: Print EREMOVE return value in __sgx_sanitize

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Date:   Thu, 25 Aug 2022 08:37:43 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     linux-sgx@...r.kernel.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] x86/sgx: Print EREMOVE return value in
 __sgx_sanitize_pages()

On Thu, Aug 25, 2022 at 08:18:27AM +0300, Jarkko Sakkinen wrote:
> In the 2nd run of __sgx_sanitize_pages() print the error
> message. All EREMOVE's should succeed. This will allow to
> provide some additional clues, if not.
> 
> Cc: Paul Menzel <pmenzel@...gen.mpg.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> ---
>  arch/x86/kernel/cpu/sgx/main.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index 515e2a5f25bb..33354921c59f 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -50,7 +50,7 @@ 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;
>  	LIST_HEAD(dirty);
> @@ -90,6 +90,9 @@ static void __sgx_sanitize_pages(struct list_head *dirty_page_list)
>  			list_del(&page->list);
>  			sgx_free_epc_page(page);
>  		} else {
> +			if (verbose)
> +				pr_err_ratelimited(EREMOVE_ERROR_MESSAGE, ret, ret);
> +
>  			/* The page is not yet clean - move to the dirty list. */
>  			list_move_tail(&page->list, &dirty);
>  		}
> @@ -394,8 +397,8 @@ static int ksgxd(void *p)
>  	 * Sanitize pages in order to recover from kexec(). The 2nd pass is
>  	 * required for SECS pages, whose child pages blocked EREMOVE.
>  	 */
> -	__sgx_sanitize_pages(&sgx_dirty_page_list);
> -	__sgx_sanitize_pages(&sgx_dirty_page_list);
> +	__sgx_sanitize_pages(&sgx_dirty_page_list, false);
> +	__sgx_sanitize_pages(&sgx_dirty_page_list, true);
>  
>  	/* sanity check: */
>  	WARN_ON(!list_empty(&sgx_dirty_page_list));
> -- 
> 2.37.1
> 

Should this also print the number of pages not eremoved?

That would render out the need for WARN_ON() at call site,
and would provide more data.

BR, Jarkko