linux-kernel - Re: [PATCHv2 03/29] x86/tdx: Add __tdx_module_call() and __tdx

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Date:   Fri, 4 Feb 2022 12:47:58 +1300
From:   Kai Huang <kai.huang@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>, <mingo@...hat.com>,
        <bp@...en8.de>, <dave.hansen@...el.com>, <luto@...nel.org>,
        <peterz@...radead.org>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <aarcange@...hat.com>, <ak@...ux.intel.com>,
        <dan.j.williams@...el.com>, <david@...hat.com>, <hpa@...or.com>,
        <jgross@...e.com>, <jmattson@...gle.com>, <joro@...tes.org>,
        <jpoimboe@...hat.com>, <knsathya@...nel.org>,
        <pbonzini@...hat.com>, <sdeep@...are.com>, <seanjc@...gle.com>,
        <tony.luck@...el.com>, <vkuznets@...hat.com>,
        <wanpengli@...cent.com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>,
        Kai Huang <kai.huang@...ux.intel.com>
Subject: Re: [PATCHv2 03/29] x86/tdx: Add __tdx_module_call() and
 __tdx_hypercall() helper functions


> > 	/*
> > 	 * SEAMCALL instruction is essentially a VMExit from VMX root
> > 	 * mode to SEAM VMX root mode.  VMfailInvalid (CF=1) indicates
> > 	 * that the targeted SEAM firmware is not loaded or disabled,
> > 	 * or P-SEAMLDR is busy with another SEAMCALL.  %rax is not
> > 	 * changed in this case.
> > 	 *
> > 	 * Set %rax to VMFAILINVALID for VMfailInvalid.  This value
> > 	 * will never be used as actual SEAMCALL error code.
> > 	 */
> > 	jnb     .Lno_vmfailinvalid
> > 	mov     $(VMFAILINVALID), %rax
> > 	jmp     .Lno_output_struct
> > 
> > .Lno_vmfailinvalid:
> 
> Okay, I will add it under .if \host.
> 
> But maybe use JNC instead of JNB? Since we check for CF flag,
> Jump-if-Not-Carry sounds more reasonable than Jump-if-Not-Below.
> Not-Below of what?

Fine with JNC :)