linux-kernel - Re: [PATCH v8 11/16] x86/virt/tdx: Designate reserved areas for all TDMRs

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]

Message-ID: <3bfe283e-6a90-54cb-1ba2-45ce6d022206@intel.com>
Date:   Tue, 10 Jan 2023 07:19:46 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v8 11/16] x86/virt/tdx: Designate reserved areas for all
 TDMRs

On 1/10/23 03:01, Huang, Kai wrote:
> On Mon, 2023-01-09 at 17:22 -0800, Dave Hansen wrote:
>> On 1/9/23 17:19, Huang, Kai wrote:
>>>> It's probably also worth noting *somewhere* that there's a balance to be
>>>> had between TDMRs and reserved areas.  A system that is running out of
>>>> reserved areas in a TDMR could split a TDMR to get more reserved areas.
>>>> A system that has run out of TDMRs could relatively easily coalesce two
>>>> adjacent TDMRs (before the PAMTs are allocated) and use a reserved area
>>>> if there was a gap between them.
>>> We can add above to the changelog of this patch, or the patch 09 ("x86/virt/tdx:
>>> Fill out TDMRs to cover all TDX memory regions").  The latter perhaps is better
>>> since that patch is the first place where the balance of TDMRs and reserved
>>> areas is related.
>>>
>>> What is your suggestion?
>> Just put it close to the code that actually hits the problem so the
>> potential solution is close at hand to whoever hits the problem.
>>
> Sorry to double check: the code which hits the problem is the 'if (idx >=
> max_reserved_per_tdmr)' check in tdmr_add_rsvd_area(), so I think I can add
> right before this check?

Please just hack together how you think it should look and either reply
with an updated patch, or paste the relevant code snippet in your reply.
 That'll keep me from having to go chase this code back down.