netdev - Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range to map as encrypted

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 9 Mar 2023 08:19:58 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw2@...radead.org>,
        Jörg Rödel <joro@...tes.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "hpa@...or.com" <hpa@...or.com>, KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
        "robh@...nel.org" <robh@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "arnd@...db.de" <arnd@...db.de>, "hch@....de" <hch@....de>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "brijesh.singh@....com" <brijesh.singh@....com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "isaku.yamahata@...el.com" <isaku.yamahata@...el.com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "jane.chu@...cle.com" <jane.chu@...cle.com>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
Subject: Re: [PATCH v5 06/14] x86/ioremap: Support hypervisor specified range
 to map as encrypted

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

>