linux-kernel - Re: [PATCH 07/25] KVM: TDX: Add helper functions to allocate/free TDX private host key id

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Message-ID: <e5dd31c924e8be70d817fe71e69d40053ae7f15a.camel@intel.com>
Date: Tue, 10 Sep 2024 16:39:31 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "seanjc@...gle.com" <seanjc@...gle.com>
CC: "Li, Xiaoyao" <xiaoyao.li@...el.com>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>, "tony.lindgren@...ux.intel.com"
	<tony.lindgren@...ux.intel.com>, "Huang, Kai" <kai.huang@...el.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/25] KVM: TDX: Add helper functions to allocate/free TDX
 private host key id

On Tue, 2024-09-10 at 18:27 +0200, Paolo Bonzini wrote:
> On 8/13/24 00:48, Rick Edgecombe wrote:
> > From: Isaku Yamahata <isaku.yamahata@...el.com>
> > 
> > Add helper functions to allocate/free TDX private host key id (HKID).
> > 
> > The memory controller encrypts TDX memory with the assigned HKIDs. Each TDX
> > guest must be protected by its own unique TDX HKID.
> > 
> > The HW has a fixed set of these HKID keys. Out of those, some are set aside
> > for use by for other TDX components, but most are saved for guest use. The
> > code that does this partitioning, records the range chosen to be available
> > for guest use in the tdx_guest_keyid_start and tdx_nr_guest_keyids
> > variables.
> > 
> > Use this range of HKIDs reserved for guest use with the kernel's IDA
> > allocator library helper to create a mini TDX HKID allocator that can be
> > called when setting up a TD. This way it can have an exclusive HKID, as is
> > required. This allocator will be used in future changes.
> 
> This is basically what Dave was asking for, isn't it?

This patch has the allocator in KVM code, and the keyid ranges exported from
arch/x86. Per the discussion with Dave we will export the allocator functions
and keep the keyid ranges in arch/x86 code.