linux-kernel - Re: [RFC RFT PATCH 1/4] hv: Leak pages if set_memory

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Date: Fri, 1 Mar 2024 20:47:12 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
	"mhklinux@...look.com" <mhklinux@...look.com>, "dave.hansen@...ux.intel.com"
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	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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	<kirill.shutemov@...ux.intel.com>, "kys@...rosoft.com" <kys@...rosoft.com>,
	"Cui, Dexuan" <decui@...rosoft.com>, "kuba@...nel.org" <kuba@...nel.org>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
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CC: "sathyanarayanan.kuppuswamy@...ux.intel.com"
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, "Reshetova, Elena"
	<elena.reshetova@...el.com>
Subject: Re: [RFC RFT PATCH 1/4] hv: Leak pages if set_memory_encrypted()
 fails

On Fri, 2024-03-01 at 20:21 +0000, Michael Kelley wrote:
> 
> The Hyper-V case can actually be a third path when a paravisor
> is being used.  In that case, for both TDX and SEV-SNP, the
> hypervisor callbacks in __set_memory_enc_pgtable() go
> to Hyper-V specific functions that talk to the paravisor. Those
> callbacks never panic. After a failure, either at the paravisor
> level or in the paravisor talking to the hypervisor/VMM, the
> decrypted/encrypted state of the memory isn't known.  So
> leaking the memory is still the right thing to do, and your
> patch set is good. But in the Hyper-V with paravisor case,
> the leaking is applicable more broadly than just TDX.
> 
> The text in the commit message isn't something that I'll
> go to the mat over.  But I wanted to offer the slightly broader
> perspective.

Oh, interesting. I think I missed it because it only has a special
enc_status_change_finish(). But yea. It does sound like the text you
suggested is more accurate. I'll update it.