linux-kernel - Re: [PATCH v19 007/130] x86/virt/tdx: Export SEAMCALL functions

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Message-ID: <Zg3L6VttYZkb7N1M@google.com>
Date: Wed, 3 Apr 2024 14:36:41 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Kai Huang <kai.huang@...el.com>, Tina Zhang <tina.zhang@...el.com>, 
	Rick P Edgecombe <rick.p.edgecombe@...el.com>, Hang Yuan <hang.yuan@...el.com>, 
	"x86@...nel.org" <x86@...nel.org>, Bo2 Chen <chen.bo@...el.com>, 
	"sagis@...gle.com" <sagis@...gle.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>, Erdem Aktas <erdemaktas@...gle.com>, 
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com" <pbonzini@...hat.com>, 
	Isaku Yamahata <isaku.yamahata@...el.com>
Subject: Re: [PATCH v19 007/130] x86/virt/tdx: Export SEAMCALL functions

On Wed, Mar 20, 2024, Dave Hansen wrote:
> On 3/20/24 05:09, Huang, Kai wrote:
> > I can try to do if you guys believe this should be done, and should be done
> > earlier than later, but I am not sure _ANY_ optimization around SEAMCALL will
> > have meaningful performance improvement.
> 
> I don't think Sean had performance concerns.
> 
> I think he was having a justifiably violent reaction to how much more
> complicated the generated code is to do a SEAMCALL versus a good ol' KVM
> hypercall.

Yep.  The code essentially violates the principle of least surprise.  I genuinely
thought I was dumping the wrong function(s) when I first looked at the output.