linux-kernel - Re: [PATCH v12 05/22] x86/virt/tdx: Add SEAMCALL infrastructure

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Message-ID: <20230628115022.2plia6tonmxxaj5x@box.shutemov.name>
Date:   Wed, 28 Jun 2023 14:50:22 +0300
From:   "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "Gao, Chao" <chao.gao@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "nik.borisov@...e.com" <nik.borisov@...e.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v12 05/22] x86/virt/tdx: Add SEAMCALL infrastructure

On Wed, Jun 28, 2023 at 03:34:05AM +0000, Huang, Kai wrote:
> On Wed, 2023-06-28 at 11:09 +0800, Chao Gao wrote:
> > > +/*
> > > + * Wrapper of __seamcall() to convert SEAMCALL leaf function error code
> > > + * to kernel error code.  @seamcall_ret and @out contain the SEAMCALL
> > > + * leaf function return code and the additional output respectively if
> > > + * not NULL.
> > > + */
> > > +static int __always_unused seamcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64
> > > r9,
> > > +				    u64 *seamcall_ret,
> > > +				    struct tdx_module_output *out)
> > > +{
> > > +	u64 sret;
> > > +	int cpu;
> > > +
> > > +	/* Need a stable CPU id for printing error message */
> > > +	cpu = get_cpu();
> > > +	sret = __seamcall(fn, rcx, rdx, r8, r9, out);
> > > +	put_cpu();
> > > +
> > > +	/* Save SEAMCALL return code if the caller wants it */
> > > +	if (seamcall_ret)
> > > +		*seamcall_ret = sret;
> > 
> > Hi Kai,
> > 
> > All callers in this series pass NULL for seamcall_ret. I am no sure if
> > you keep it intentionally.
> 
> In this series all the callers doesn't need seamcall_ret.

I'm fine keeping it if it is needed by KVM TDX enabling. Otherwise, just
drop it.

> > > +
> > > +	switch (sret) {
> > > +	case 0:
> > > +		/* SEAMCALL was successful */
> > 
> > Nit: if you add
> > 
> > #define TDX_SUCCESS	0
> > 
> > and do
> > 
> > 	case TDX_SUCCESS:
> > 		return 0;
> > 
> > then the code becomes self-explanatory. i.e., you can drop the comment.
> 
> If using this, I ended up with below:
> 
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -23,6 +23,8 @@
>  #define TDX_SEAMCALL_GP                        (TDX_SW_ERROR | X86_TRAP_GP)
>  #define TDX_SEAMCALL_UD                        (TDX_SW_ERROR | X86_TRAP_UD)
>  
> +#define TDX_SUCCESS           0
> +
> 
> Hi Kirill/Dave/David,
> 
> Are you happy with this?

Sure, looks good.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov