Message-ID: <a4fc8686-f82d-370e-309f-d6d3fc0568e8@amd.com>
Date:   Thu, 9 Mar 2023 08:19:58 -0600
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Subject: Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted
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To:     Borislav Petkov <bp@alien8.de>,
        David Woodhouse <dwmw2@infradead.org>,
        =?UTF-8?B?SsO2cmcgUsO2ZGVs?= <joro@8bytes.org>
Cc:     Dave Hansen <dave.hansen@intel.com>,
        "Michael Kelley (LINUX)" <mikelley@microsoft.com>,
        Sean Christopherson <seanjc@google.com>,
        "hpa@zytor.com" <hpa@zytor.com>, KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
        "luto@kernel.org" <luto@kernel.org>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "edumazet@google.com" <edumazet@google.com>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "lpieralisi@kernel.org" <lpieralisi@kernel.org>,
        "robh@kernel.org" <robh@kernel.org>, "kw@linux.com" <kw@linux.com>,
        "bhelgaas@google.com" <bhelgaas@google.com>,
        "arnd@arndb.de" <arnd@arndb.de>, "hch@lst.de" <hch@lst.de>,
        "m.szyprowski@samsung.com" <m.szyprowski@samsung.com>,
        "robin.murphy@arm.com" <robin.murphy@arm.com>,
        "brijesh.singh@amd.com" <brijesh.singh@amd.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        Tianyu Lan <Tianyu.Lan@microsoft.com>,
        "kirill.shutemov@linux.intel.com" <kirill.shutemov@linux.intel.com>,
        "sathyanarayanan.kuppuswamy@linux.intel.com" 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        "ak@linux.intel.com" <ak@linux.intel.com>,
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        "jane.chu@oracle.com" <jane.chu@oracle.com>,
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        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
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        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
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From:   Tom Lendacky <thomas.lendacky@amd.com>
In-Reply-To: <20230309115937.GAZAnKKRef99EwOu/S@fat_crate.local>
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On 3/9/23 05:59, Borislav Petkov wrote:
> First of all,
> 
> thanks for proactively pointing that out instead of simply using what's
> there and we get to find out later, only by chance.
> 
> Much appreciated. :-)
> 
> On Thu, Mar 09, 2023 at 11:12:10AM +0000, David Woodhouse wrote:
>>> Right, I think we're ok with the following basic rules:
>>>
>>> - pure arch/x86/ code should use the x86_platform function pointers to
>>>    query hypervisor capabilities/peculiarities
>>>
>>> - cc_platform_has() should be used in generic/driver code as it
>>>    abstracts away the underlying platform better. IOW, querying
>>>    x86_platform.... in generic, platform-agnostic driver code looks weird to
>>>    say the least
>>>
>>> The hope is that those two should be enough to support most guest types
>>> and not let the zoo get too much out of hand...
>>>
>>> Thx.
>>
>> In
>> https://lore.kernel.org/all/20230308171328.1562857-13-usama.arif@bytedance.com/
>> I added an sev_es_active() helper for x86 code.
>>
>> Is that consistent with the vision here, or should I do something different?
> 
> So looking at sev_es_init_vc_handling() where we set that key, I'm
> *thinking* that key can be removed now and the code should check
> 
>    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)
> 
> instead.
> 
> Because if some of the checks in that function below fail, the guest
> will terminate anyway.
> 
> Jörg, Tom?

I believe Joerg added that key for performance reasons, since it is used 
on the exception path and can avoid all the calls to cc_platform_has(). I 
think that key should stay.

Maybe David can introduce an CC_ATTR_GUEST_SEV_ES attribute that returns 
true if the guest is an ES or SNP guest. Or do we introduce a 
CC_ATTR_PARALLEL_BOOT attribute that returns true for any SEV guest.

Then the "if cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT) && !has_sev_es" 
check in arch/x86/kernel/smpboot.c can be removed and the following check 
can become if (x2apic_mode || cc_platform_has(CC_ATTR_PARALLEL_BOOT))

Not sure how that affects a TDX guest, though.

Thanks,
Tom

>