linux-kernel - Re: [PATCH v3 13/14] x86/sev: Hide SVSM attestation entries if not running under an SVSM

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Message-ID: <18dfff9a-b8e0-9d43-8538-366f74d74a7d@amd.com>
Date: Tue, 16 Apr 2024 11:10:14 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Dan Williams <dan.j.williams@...el.com>, linux-kernel@...r.kernel.org,
 x86@...nel.org, linux-coco@...ts.linux.dev, svsm-devel@...onut-svsm.dev
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Michael Roth <michael.roth@....com>,
 Ashish Kalra <ashish.kalra@....com>, Joel Becker <jlbec@...lplan.org>,
 Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v3 13/14] x86/sev: Hide SVSM attestation entries if not
 running under an SVSM

On 4/16/24 01:03, Dan Williams wrote:
> Tom Lendacky wrote:
>> Config-fs provides support to hide individual attribute entries. Using
>> this support, base the display of the SVSM related entries on the presence
>> of an SVSM.
>>
>> Cc: Joel Becker <jlbec@...lplan.org>
>> Cc: Christoph Hellwig <hch@....de>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>>   arch/x86/coco/core.c        |  4 ++++
>>   drivers/virt/coco/tsm.c     | 14 ++++++++++----
>>   include/linux/cc_platform.h |  8 ++++++++
>>   3 files changed, 22 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
>> index d07be9d05cd0..efa0f648f754 100644
>> --- a/arch/x86/coco/core.c
>> +++ b/arch/x86/coco/core.c
>> @@ -12,6 +12,7 @@
>>   
>>   #include <asm/coco.h>
>>   #include <asm/processor.h>
>> +#include <asm/sev.h>
>>   
>>   enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
>>   u64 cc_mask __ro_after_init;
>> @@ -78,6 +79,9 @@ static bool noinstr amd_cc_platform_has(enum cc_attr attr)
>>   	case CC_ATTR_GUEST_STATE_ENCRYPT:
>>   		return sev_status & MSR_AMD64_SEV_ES_ENABLED;
>>   
>> +	case CC_ATTR_GUEST_SVSM_PRESENT:
>> +		return snp_get_vmpl();
>> +
>>   	/*
>>   	 * With SEV, the rep string I/O instructions need to be unrolled
>>   	 * but SEV-ES supports them through the #VC handler.
>> diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm.c
>> index 46f230bf13ac..d30471874e87 100644
>> --- a/drivers/virt/coco/tsm.c
>> +++ b/drivers/virt/coco/tsm.c
>> @@ -64,6 +64,12 @@ static struct tsm_report_state *to_state(struct tsm_report *report)
>>   	return container_of(report, struct tsm_report_state, report);
>>   }
>>   
>> +static bool provider_visibility(const struct config_item *item,
>> +				const struct configfs_attribute *attr)
>> +{
>> +	return cc_platform_has(CC_ATTR_GUEST_SVSM_PRESENT);
>> +}
> 
> I expect this needs to be a callback into the provider ops because one
> of the other use cases for this visibility check is to get rid of the
> "extra" attributes and handle that visibility with the same mechanism.

Yes, worked through on the other thread.

But the "extra" attributes are likely to remain visible if we go in the 
group visibility direction, to provide compatibility.

Thanks,
Tom