linux-kernel - Re: [PATCH] tee: amdtee: add support for use of cma region

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b908433c-0924-fbf7-f555-532e438ff050@intel.com>
Date:   Fri, 18 Aug 2023 08:26:09 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Devaraj Rangasamy <Devaraj.Rangasamy@....com>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        Rijo Thomas <Rijo-john.Thomas@....com>,
        SivaSangeetha SK <SivaSangeetha.SK@....com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Juergen Gross <jgross@...e.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Ross Lagerwall <ross.lagerwall@...rix.com>,
        Yuntao Wang <ytcoode@...il.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Tom Lendacky <thomas.lendacky@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        op-tee@...ts.trustedfirmware.org
Cc:     Mythri PK <Mythri.Pandeshwarakrishna@....com>,
        Nimesh Easow <Nimesh.Easow@....com>
Subject: Re: [PATCH] tee: amdtee: add support for use of cma region

On 8/18/23 07:42, Devaraj Rangasamy wrote:
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1223,6 +1223,8 @@ void __init setup_arch(char **cmdline_p)
>  	initmem_init();
>  	dma_contiguous_reserve(max_pfn_mapped << PAGE_SHIFT);
>  
> +	amdtee_cma_reserve();
> +
>  	if (boot_cpu_has(X86_FEATURE_GBPAGES))
>  		hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);

Right now, we have *A* global CMA pool set up in
dma_contiguous_reserve() that everyone shares.

Why does this *one* driver deserve to be a special snowflake and get its
own private CMA area and own command-line options?

It seems to me like you should just tell users to set
CONFIG_CMA_SIZE_MBYTES or use cma=size on the command-line and just use
the global pool.  If you want to make it a special snowflake, there's a
much higher bar to clear, and there's zero justification for that right now.

Oh, and this:

>  static int pool_op_alloc(struct tee_shm_pool *pool, struct tee_shm *shm,
>  			 size_t size, size_t align)
>  {
>  	unsigned int order = get_order(size);
>  	unsigned long va;
>  	int rc;
>  
>  	/*
>  	 * Ignore alignment since this is already going to be page aligned
>  	 * and there's no need for any larger alignment.
>  	 */
> 	va = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);

is goofy.  It either only needs powers-of-2 and can take "order" as an
argument instead of 'size', or it should be using alloc_pages_exact() to
avoid wasting memory.