linux-kernel - Re: [PATCH v6 6/6] drivers/node: Show in sysfs node's crypto capabilities

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Message-ID: <5c5ffe29-d3d3-2955-cf78-ad275110f012@amd.com>
Date:   Fri, 4 Feb 2022 09:59:45 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Martin Fernandez <martin.fernandez@...ypsium.com>,
        "Limonciello, Mario" <mario.limonciello@....com>
Cc:     linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        platform-driver-x86@...r.kernel.org, linux-mm@...ck.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        ardb@...nel.org, dvhart@...radead.org, andy@...radead.org,
        gregkh@...uxfoundation.org, rafael@...nel.org, rppt@...nel.org,
        akpm@...ux-foundation.org, daniel.gutson@...ypsium.com,
        hughsient@...il.com, alex.bazhaniuk@...ypsium.com,
        alison.schofield@...el.com, keescook@...omium.org
Subject: Re: [PATCH v6 6/6] drivers/node: Show in sysfs node's crypto
 capabilities

On 2/4/22 07:21, Martin Fernandez wrote:
> On 2/4/22, Limonciello, Mario <mario.limonciello@....com> wrote:
>> On 2/3/2022 10:43, Martin Fernandez wrote:
>>> +static ssize_t crypto_capable_show(struct device *dev,
>>> +				   struct device_attribute *attr, char *buf)
>>> +{
>>> +	struct pglist_data *pgdat = NODE_DATA(dev->id);
>>> +
>>> +	return sysfs_emit(buf, "%d\n", pgdat->crypto_capable);
>>
>> As there is interest in seeing these capabilities from userspace, it
>> seems like a logical time to also expose a `crypto_active` attribute.
> 
> I planned to do something similar to this, but to show (or actually
> hide if inactive) tme in cpuinfo, just as Borislav Petkov suggested a
> few versions back.
> 
> https://lore.kernel.org/linux-efi/YXrnkxgdjWbcPlJA@zn.tnic/
> 
>> Then userspace can make a judgement call if the system supports crypto
>> memory (`crypto_capable`) and then also whether or not it's been turned
>> on (`crypto_active`).
>>
>> `crypto_active` could be detected with some existing support in the
>> kernel of `mem_encrypt_active()`.  This will then work for a variety of
>> architectures too that offer `mem_encrypt_active()`.
> 
> I need a hand with this, I grepped for mem_encrypt_active and nothing
> showed up...

The mem_encrypt_active() function has been replaced by 
cc_platform_has(CC_ATTR_MEM_ENCRYPT).

> 
>> As it stands today the only reliable way to tell from userspace (at
>> least for AMD's x86 implementation) is by grepping the system log for
>> the line "AMD Memory Encryption Features active".
> 
> Isn't enough to grep for sme/sev in cpuinfo?

No, it's not enough. Cpuinfo shows a processors capabilities and not 
necessarily whether that capability is being used.

Thanks,
Tom