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Message-ID: <97ace776b756312de05d3a9c8b1ca251e714db17.camel@intel.com>
Subject: Re: [PATCH v8 2/5] x86/tdx: Add TDX Guest event notify interrupt
 support
From:   Kai Huang <kai.huang@intel.com>
To:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org
Cc:     "H . Peter Anvin" <hpa@zytor.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Wander Lairson Costa <wander@redhat.com>,
        Isaku Yamahata <isaku.yamahata@gmail.com>,
        marcelo.cerri@canonical.com, tim.gardner@canonical.com,
        khalid.elmously@canonical.com, philip.cox@canonical.com,
        linux-kernel@vger.kernel.org,
        "Nakajima, Jun" <jun.nakajima@intel.com>
Date:   Thu, 23 Jun 2022 22:24:29 +1200
In-Reply-To: <efb2cdab-289b-8757-fe5e-5348519b0474@linux.intel.com>
References: <20220609025220.2615197-1-sathyanarayanan.kuppuswamy@linux.intel.com>
         <20220609025220.2615197-3-sathyanarayanan.kuppuswamy@linux.intel.com>
         <78873cc1db47ba00a4c01f38290521c1a6072820.camel@intel.com>
         <efb2cdab-289b-8757-fe5e-5348519b0474@linux.intel.com>
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On Mon, 2022-06-20 at 08:44 -0700, Sathyanarayanan Kuppuswamy wrote:
> I agree that event notification is currently only used for attestation. B=
ut I
> think in future there could be other use cases for it.=C2=A0
>=20

We have TDVMCALL<Service> in GHCI 1.5.  It allows specifying the vector.  I
don't know whether there's any future case that still needs
SetupEventNotifyInterrupt.

> If the intention is just
> to use it for attestation, then we can just modify the GetQuote TDVMCALL =
to pass
> the vector address, and there is no need for new TDVMCALL.=20

The TDVMCALL<Service> in GHCI 1.5 actually supports specifying the vector. =
 It
currently neither clearly says "the VMM should inject event to the vCPU on =
which
the TDVMCALL<Service> is called", nor it allows specifying which vCPU to in=
ject.
Assuming we can lobby (I am already lobbying, actually) to make either way,=
 in
fact I think it can be used as IRQ way (like I described in my first reply)=
.

I once lobbied to completely remove GetQuote (and SetupEventNotifyInterrupt=
)
from GHCI 1.0 and move TDVMCALL<Service> from GHCI 1.5 to 1.0, and define a=
 new
sub-service for attestation -- GetQuote will be one command then, and we ca=
n
define more attestation related commands (which is likely) when needed.  I
believe using TDVMCALL<Service> for GetQuote can actually allow kernel to u=
se
IRQ way, but doesn't need a system vector.  But this wasn't successful.


--=20
Thanks,
-Kai