linux-kernel - Re: [PATCH 07/13] x86/virt/tdx: Add SEAMCALL wrapper tdh_mem_sept

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Message-ID: <753cd9f1-5eb7-480f-ae4f-d263aaecdd6c@intel.com>
Date: Tue, 7 Jan 2025 11:48:12 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
 "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
 "pbonzini@...hat.com" <pbonzini@...hat.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: "Zhao, Yan Y" <yan.y.zhao@...el.com>,
 "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
 "Huang, Kai" <kai.huang@...el.com>,
 "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
 "Yamahata, Isaku" <isaku.yamahata@...el.com>
Subject: Re: [PATCH 07/13] x86/virt/tdx: Add SEAMCALL wrapper
 tdh_mem_sept_add() to add SEPT pages

On 1/2/25 13:59, Edgecombe, Rick P wrote:
> union tdx_sept_gpa_mapping_info {
> 	struct {
> 		u64 level	: 3;
> 		u64 reserved1	: 9;
> 		u64 gfn		: 40;
> 		u64 reserved2	: 12;
> 	};
> 	u64 full;
> };

This is functionally OK, but seeing bitfields on a value that's probably
going to get shifted around makes me nervous because of:

> https://lore.kernel.org/lkml/20231111020019.553664-1-michael.roth@amd.com/
I wouldn't NAK it just for this, but it's also not how I would code it up.