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

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Date:   Fri, 4 Feb 2022 10:21:50 -0300
From:   Martin Fernandez <martin.fernandez@...ypsium.com>
To:     "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,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>
Subject: Re: [PATCH v6 6/6] drivers/node: Show in sysfs node's crypto capabilities

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...

> 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?