linux-kernel - Re: [PATCH v2 08/25] x86/virt/tdx: Add SEAMCALL wrappers for TDX page cache management

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Message-ID: <3f9752a1-53c1-4be0-a3a0-8be25d603dc2@intel.com>
Date: Thu, 14 Nov 2024 13:21:56 +1300
From: "Huang, Kai" <kai.huang@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "Hansen, Dave" <dave.hansen@...el.com>,
	"seanjc@...gle.com" <seanjc@...gle.com>
CC: "Yao, Yuan" <yuan.yao@...el.com>, "binbin.wu@...ux.intel.com"
	<binbin.wu@...ux.intel.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"tony.lindgren@...ux.intel.com" <tony.lindgren@...ux.intel.com>,
	"sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Chatre, Reinette"
	<reinette.chatre@...el.com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"Zhao, Yan Y" <yan.y.zhao@...el.com>
Subject: Re: [PATCH v2 08/25] x86/virt/tdx: Add SEAMCALL wrappers for TDX page
 cache management



On 14/11/2024 11:00 am, Edgecombe, Rick P wrote:
> On Wed, 2024-11-13 at 13:50 -0800, Dave Hansen wrote:
>> On 11/13/24 13:44, Edgecombe, Rick P wrote:
>>> Moving them to arch/x86 means we need to translate some things between KVM's
>>> parlance and the rest of the kernels. This is extra wrapping. Another example
>>> that was used in the old SEAMCALL wrappers was gpa_t, which KVM uses to refers
>>> to a guest physical address. void * to the host direct map doesn't fit, so we
>>> are back to u64 or a new gpa struct (like in the other thread) to speak to the
>>> arch/x86 layers.
>>
>> I have zero issues with non-core x86 code doing a #include
>> <linux/kvm_types.h>.  Why not just use the KVM types?
> 
> You know...I assumed it wouldn't work because of some internal headers. But yea.
> Nevermind, we can just do that. Probably because the old code also referred to
> struct kvm_tdx, it just got fully separated. Kai did you attempt this path at
> all?

'struct kvm_tdx' is a KVM internal structure so we cannot use that in 
SEAMCALL wrappers in the x86 core.  If you are talking about just use 
KVM types like 'gfn_t/hpa_t' etc (by including <linux/kvm_types.h>) 
perhaps this is fine.

But I didn't try to do in this way.  We can try if that's better, but I 
suppose we should get Sean/Paolo's feedback here?