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

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Date: Thu, 25 Apr 2024 19:46:21 +0300
From: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Rick P Edgecombe <rick.p.edgecombe@...el.com>, 
	Tina Zhang <tina.zhang@...el.com>, Dave Hansen <dave.hansen@...el.com>, 
	Hang Yuan <hang.yuan@...el.com>, "x86@...nel.org" <x86@...nel.org>, 
	Kai Huang <kai.huang@...el.com>, 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 Fri, Apr 19, 2024 at 12:53:19PM -0700, Sean Christopherson wrote:
> > But I guess we can make a *few* wrappers that covers all needed cases.
> 
> Yeah.  I suspect two will suffice.  One for the calls that say at or below four
> inputs, and one for the fat ones like ReportFatalError that use everything under
> the sun.

I ended up with three helpers:

  - tdvmcall_trampoline() as you proposed.
  
  - tdvmcall_report_fatal_error() that does ReportFatalError specificly.
    Pointer to char array as an input. Never returns: no need to
    save/restore registers.

  - hv_tdx_hypercall(). Hyper-V annoyingly uses R8 and RDX as parameters :/

> Not sure, haven't looked at them recently.  At a glance, something similar?  The
> use of high registers instead of RDI and RSI is damn annoying :-/

I defined three helpers: TDCALL_0(), TDCALL_1() and TDCALL_5(). All takes 4
input arguments.

I've updated the WIP branch with the new version:

https://github.com/intel/tdx/commits/guest-tdx-asm/

Any feedback is welcome.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov