From: Tom Lendacky <thomas.lendacky@amd.com>
To: Borislav Petkov <bp@alien8.de>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
linux-coco@lists.linux.dev, svsm-devel@coconut-svsm.dev,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Dan Williams <dan.j.williams@intel.com>,
Michael Roth <michael.roth@amd.com>,
Ashish Kalra <ashish.kalra@amd.com>
Subject: Re: [PATCH v4 05/15] x86/sev: Use kernel provided SVSM Calling Areas
Date: Wed, 8 May 2024 15:09:02 -0500 [thread overview]
Message-ID: <d3b59450-fdbd-2813-bbc0-58f9dc2ba817@amd.com> (raw)
In-Reply-To: <20240508195842.GIZjvZcpRz0bdkiPWA@fat_crate.local>
On 5/8/24 14:58, Borislav Petkov wrote:
> On Wed, May 08, 2024 at 02:13:17PM -0500, Tom Lendacky wrote:
>> ok, maybe __perform_svsm_msr_protocol or such.
>
> We'll bikeshed it in the coming weeks.
:)
>
>> There's quite a bit of interaction so I'll make sure to prefix everything.
>
> Ack.
>
>> The paravirt versions of local_irq_save and local_irq_restore can't be used
>> as early as this routine is called.
>
> tglx says you should do native_local_irq_save()/.._restore() helpers
> just like the arch_local_irq_save()/..._restore() ones but use only
> native_ functions without the paravirt gunk.
>
> In a prepatch pls.
Will do.
>
>>>> + struct svsm_call call = {};
>>>> + int ret;
>>>> + u64 pa;
>>>> +
>>>> + /*
>>>> + * Record the SVSM Calling Area address (CAA) if the guest is not
>>>> + * running at VMPL0. The CA will be used to communicate with the
>>>> + * SVSM to perform the SVSM services.
>>>> + */
>>>> + setup_svsm_ca(cc_info);
>>>> +
>>>> + /* Nothing to do if not running under an SVSM. */
>>>> + if (!vmpl)
>>>> + return;
>>>
>>> You set up stuff above and now you bail out?
>>
>> setup_svsm_ca() is what sets the vmpl variable. So nothing will have been
>> setup if the VMPL is zero, in which case we don't continue on.
>
> You still assign
>
> /*
> * The CA is identity mapped when this routine is called, both by the
> * decompressor code and the early kernel code.
> */
> boot_svsm_caa = (struct svsm_ca *)caa;
> boot_svsm_caa_pa = caa;
>
> regardless of vmpl.
If we're not running at VMPL0 (based on the RMPADJUST check) and if the
SVSM doesn't advertise a non-zero VMPL value, we will self-terminate. So
those values are only set if we are not running at VMPL0 and the SVSM
has provided a non-zero value to us.
I'm going to turn the function into a bool function so that the call
becomes:
if (!svsm_setup_caa(cc_info))
return;
>
> I think you should assign those only when vmpl != 0.
I do. I think you're missing the RMPADJUST check that causes the
function to return early if we're running at VMPL0.
>
> Otherwise the code is confusing.
>
>>> Judging by setup_svsm_ca() you don't really need that vmpl var but you
>>> can check
>>>
>>> if (!boot_svsm_caa)
>>> return;
>>>
>>> to determine whether a SVSM was detected.
>>
>> Yes, but the vmpl var will be used for attestation requests, sysfs, etc.
>
> I guess that comes later in the patchset...
>
>>> Huh, setup_svsm_ca() already assigned those...
>>
>> setup_svsm_ca() assigned the ones from the secrets page. The kernel now
>> switches to using its own CA.
>
> Comment pls.
There's a block comment above it all, but maybe it isn't clear enough.
I'll rework it.
Thanks,
Tom
>
> Thx.
>
next prev parent reply other threads:[~2024-05-08 20:09 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-24 15:57 [PATCH v4 00/15] Provide SEV-SNP support for running under an SVSM Tom Lendacky
2024-04-24 15:57 ` [PATCH v4 01/15] x86/sev: Shorten snp_secrets_page_layout to snp_secrets_page Tom Lendacky
2024-04-25 13:30 ` Borislav Petkov
2024-04-24 15:57 ` [PATCH v4 02/15] x86/sev: Rename snp_init() in the boot/compressed/sev.c file Tom Lendacky
2024-04-24 15:57 ` [PATCH v4 03/15] x86/sev: Make the VMPL0 checking more straight forward Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 04/15] x86/sev: Check for the presence of an SVSM in the SNP Secrets page Tom Lendacky
2024-05-02 9:35 ` Borislav Petkov
2024-05-02 15:29 ` Tom Lendacky
2024-05-17 15:58 ` Borislav Petkov
2024-05-20 13:57 ` Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 05/15] x86/sev: Use kernel provided SVSM Calling Areas Tom Lendacky
2024-05-03 10:34 ` Borislav Petkov
2024-05-06 10:09 ` Borislav Petkov
2024-05-06 13:14 ` Tom Lendacky
2024-05-06 14:14 ` Borislav Petkov
2024-05-08 8:05 ` Borislav Petkov
2024-05-08 19:13 ` Tom Lendacky
2024-05-08 19:40 ` Tom Lendacky
2024-05-08 19:58 ` Borislav Petkov
2024-05-08 20:09 ` Tom Lendacky [this message]
2024-05-17 19:23 ` Borislav Petkov
2024-04-24 15:58 ` [PATCH v4 06/15] x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0 Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 07/15] x86/sev: Use the SVSM to create a vCPU when not in VMPL0 Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 08/15] x86/sev: Provide SVSM discovery support Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 09/15] x86/sev: Provide guest VMPL level to userspace Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 10/15] virt: sev-guest: Choose the VMPCK key based on executing VMPL Tom Lendacky
2024-05-01 23:57 ` [svsm-devel] " Jacob Xu
2024-05-02 13:17 ` Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 11/15] configfs-tsm: Allow the privlevel_floor attribute to be updated Tom Lendacky
2024-04-26 20:51 ` Dan Williams
2024-04-24 15:58 ` [PATCH v4 12/15] fs/configfs: Add a callback to determine attribute visibility Tom Lendacky
2024-04-26 21:48 ` Dan Williams
2024-04-29 13:26 ` Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 13/15] x86/sev: Take advantage of configfs visibility support in TSM Tom Lendacky
2024-04-26 21:58 ` Dan Williams
2024-04-29 13:35 ` Tom Lendacky
2024-04-29 14:28 ` Tom Lendacky
2024-05-01 19:28 ` Dan Williams
2024-05-01 5:18 ` Kuppuswamy Sathyanarayanan
2024-05-01 20:15 ` Dan Williams
2024-05-02 3:40 ` Kuppuswamy Sathyanarayanan
2024-05-02 17:29 ` Dan Williams
2024-05-03 16:10 ` Kuppuswamy Sathyanarayanan
2024-04-24 15:58 ` [PATCH v4 14/15] x86/sev: Extend the config-fs attestation support for an SVSM Tom Lendacky
2024-04-24 15:58 ` [PATCH v4 15/15] x86/sev: Allow non-VMPL0 execution when an SVSM is present Tom Lendacky
2024-05-03 11:37 ` [svsm-devel] " Jörg Rödel
2024-05-03 16:04 ` Borislav Petkov
2024-05-06 7:43 ` Jörg Rödel
2024-05-03 11:38 ` [svsm-devel] [PATCH v4 00/15] Provide SEV-SNP support for running under an SVSM Jörg Rödel
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