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Message-ID: <20230803121207.krvcuj22mdxhugog@box.shutemov.name>
Date: Thu, 3 Aug 2023 15:12:07 +0300
From: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
To: "Huang, Kai" <kai.huang@...el.com>
Cc: "Hansen, Dave" <dave.hansen@...el.com>,
"Christopherson,, Sean" <seanjc@...gle.com>,
"x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
"peterz@...radead.org" <peterz@...radead.org>,
"hpa@...or.com" <hpa@...or.com>,
"mingo@...hat.com" <mingo@...hat.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"pbonzini@...hat.com" <pbonzini@...hat.com>,
"Yamahata, Isaku" <isaku.yamahata@...el.com>,
"sathyanarayanan.kuppuswamy@...ux.intel.com"
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
"n.borisov.lkml@...il.com" <n.borisov.lkml@...il.com>
Subject: Re: [PATCH v3 07/12] x86/tdx: Make TDX_HYPERCALL asm similar to
TDX_MODULE_CALL
On Thu, Aug 03, 2023 at 11:56:40AM +0000, Huang, Kai wrote:
> On Thu, 2023-08-03 at 14:45 +0300, kirill.shutemov@...ux.intel.com wrote:
> > > > I would rather keep the struct
> > > > read-only where possible.
> > > >
> > >
> > > We can achieve this if there's a clean way to do, but I don't see that.
> >
> > Keep _ret() and non-_ret() versions?
>
> The problem is the assembly needs to always turn on the "\ret" so that the R10
> (used as VP.VMCALL leaf return code) can be saved to the structure. Otherwise
> we are not able to return VP.VMCALL leaf return code.
Yeah. This is downside of single assembly macro for all calls.
One possible way is to make it in C: non-_ret() version pass to the
assembly helper copy of the caller's struct, keeping original intact.
But, yeah, it is ugly.
--
Kiryl Shutsemau / Kirill A. Shutemov
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