linux-kernel - RE: [PATCH v2 2/5] Drivers: hv: vmbus: Track decrypted status in vmbus

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Date: Thu, 14 Mar 2024 13:56:27 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	"rick.p.edgecombe@...el.com" <rick.p.edgecombe@...el.com>,
	"kys@...rosoft.com" <kys@...rosoft.com>, "haiyangz@...rosoft.com"
	<haiyangz@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
	"decui@...rosoft.com" <decui@...rosoft.com>, "gregkh@...uxfoundation.org"
	<gregkh@...uxfoundation.org>, "davem@...emloft.net" <davem@...emloft.net>,
	"edumazet@...gle.com" <edumazet@...gle.com>, "kuba@...nel.org"
	<kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>
CC: "elena.reshetova@...el.com" <elena.reshetova@...el.com>
Subject: RE: [PATCH v2 2/5] Drivers: hv: vmbus: Track decrypted status in
 vmbus_gpadl

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> 
> >>> @@ -886,6 +901,8 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, struct vmbus_gpadl *gpad
> >>>  	if (ret)
> >>>  		pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret);
> >>
> >> Will this be called only if vmbus_establish_gpad() is successful? If not, you
> >> might want to skip set_memory_encrypted() call for decrypted = false case.
> >
> > It's only called if vmbus_establish_gpadl() is successful.  I agree
> > we don't want to call set_memory_encrypted() if the
> > set_memory_decrypted() wasn't executed or it failed.  But
> > vmbus_teardown_gpadl() is never called with decrypted = false.
> 
> Since you rely on  vmbus_teardown_gpadl() callers, personally I think it
> is better to add that check. It is up to you.
> 

In my judgment, a check isn't really necessary.  The structure of the GPADL
code has been stable for a long time, and I'm not aware of anything
pending that would motivate a change.  And if something did change
to call vmbus_teardown_gpadl() with the memory still encrypted,
the call to set_memory_encrypted() will cause an immediate error and
a WARN_ONCE from Rick's patch to __set_memory_enc_pgtable().
The problem won't go unnoticed.

Michael