linux-kernel - Re: [PATCH v5 07/22] x86/virt/tdx: Implement SEAMCALL function

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Message-ID: <069a062e-a4a6-09af-7b74-7f4929f2ec0b@intel.com>
Date:   Fri, 24 Jun 2022 11:38:06 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kai Huang <kai.huang@...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 v5 07/22] x86/virt/tdx: Implement SEAMCALL function

On 6/22/22 04:16, Kai Huang wrote:
> SEAMCALL instruction causes #GP when SEAMRR isn't enabled, and #UD when
> CPU is not in VMX operation.  The TDX_MODULE_CALL macro doesn't handle
> SEAMCALL exceptions.  Leave to the caller to guarantee those conditions
> before calling __seamcall().

I was trying to make the argument earlier that you don't need *ANY*
detection for TDX, other than the ability to make a SEAMCALL.
Basically, patch 01/22 could go away.

You are right that:

	The TDX_MODULE_CALL macro doesn't handle SEAMCALL exceptions.

But, it's also not hard to make it *able* to handle exceptions.

So what does patch 01/22 buy us?  One EXTABLE entry?