linux-kernel - Re: [RFC PATCH v2 05/18] KVM: TDX: Drop superfluous page pinning in S-EPT management

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: <d6c4e27a70fa66b237f625ec55ffb7b1ddbcd779.camel@intel.com>
Date: Fri, 29 Aug 2025 22:59:58 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "seanjc@...gle.com" <seanjc@...gle.com>
CC: "Huang, Kai" <kai.huang@...el.com>, "ackerleytng@...gle.com"
	<ackerleytng@...gle.com>, "Annapurve, Vishal" <vannapurve@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Zhao, Yan Y"
	<yan.y.zhao@...el.com>, "Weiny, Ira" <ira.weiny@...el.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "michael.roth@....com" <michael.roth@....com>
Subject: Re: [RFC PATCH v2 05/18] KVM: TDX: Drop superfluous page pinning in
 S-EPT management

On Fri, 2025-08-29 at 15:58 -0700, Sean Christopherson wrote:
> > I was thinking about the BUSY error code avoidance logic that is now called
> > tdh_do_no_vcpus(). We assume no new conditions will appear that cause a
> > TDX_OPERAND_BUSY. Like a guest opt-in or something.
> 
> Ah, gotcha.  If that happens, that's a TDX-Module ABI break.  Probably a good
> idea to drill it into the TDX-Module authors/designers that ABI is established
> when behavior is visible to the user, regardless of whether or not that
> behavior is formally defined.
> 
> Note, breaking ABI _can_ be fine, e.g. if the behavior of some SEAMCALL
> changes, but KVM doesn't care.  But if the TDX-Module suddenly starts failing
> a SEAMCALL that previously succeeded, then we're going to have a problem.

Thanks! I'll use this quote.