linux-kernel - Re: [PATCH v3 06/21] x86/virt/tdx: Shut down TDX module in case of error

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Message-ID: <345753e50e4c113b1dfb71bba1ed841eee55aed3.camel@intel.com>
Date:   Wed, 27 Apr 2022 12:06:32 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, pbonzini@...hat.com, len.brown@...el.com,
        tony.luck@...el.com, rafael.j.wysocki@...el.com,
        reinette.chatre@...el.com, dan.j.williams@...el.com,
        peterz@...radead.org, ak@...ux.intel.com,
        kirill.shutemov@...ux.intel.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        isaku.yamahata@...el.com
Subject: Re: [PATCH v3 06/21] x86/virt/tdx: Shut down TDX module in case of
 error

On Tue, 2022-04-26 at 13:59 -0700, Dave Hansen wrote:
> On 4/5/22 21:49, Kai Huang wrote:
> > TDX supports shutting down the TDX module at any time during its
> > lifetime.  After TDX module is shut down, no further SEAMCALL can be
> > made on any logical cpu.
> 
> Is this strictly true?
> 
> I thought SEAMCALLs were used for the P-SEAMLDR too.

Sorry will change to no TDX module SEAMCALL can be made on any logical cpu.

[...]

> >  
> > +/* Data structure to make SEAMCALL on multiple CPUs concurrently */
> > +struct seamcall_ctx {
> > +	u64 fn;
> > +	u64 rcx;
> > +	u64 rdx;
> > +	u64 r8;
> > +	u64 r9;
> > +	atomic_t err;
> > +	u64 seamcall_ret;
> > +	struct tdx_module_output out;
> > +};
> > +
> > +static void seamcall_smp_call_function(void *data)
> > +{
> > +	struct seamcall_ctx *sc = data;
> > +	int ret;
> > +
> > +	ret = seamcall(sc->fn, sc->rcx, sc->rdx, sc->r8, sc->r9,
> > +			&sc->seamcall_ret, &sc->out);
> > +	if (ret)
> > +		atomic_set(&sc->err, ret);
> > +}
> > +
> > +/*
> > + * Call the SEAMCALL on all online cpus concurrently.
> > + * Return error if SEAMCALL fails on any cpu.
> > + */
> > +static int seamcall_on_each_cpu(struct seamcall_ctx *sc)
> > +{
> > +	on_each_cpu(seamcall_smp_call_function, sc, true);
> > +	return atomic_read(&sc->err);
> > +}
> 
> Why bother returning something that's not read?

It's not needed.  I'll make it void.

Caller can check seamcall_ctx::err directly if they want to know whether any
error happened.



-- 
Thanks,
-Kai