Re: [PATCH v1] x86/hvm: Generic instruction re-execution mechanism for execute faults

From: Alexandru Stefan ISAILA <aisaila@bitdefender.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>,
	"Razvan Cojocaru" <rcojocaru@bitdefender.com>
Cc: "kevin.tian@intel.com" <kevin.tian@intel.com>,
	"tamas@tklengyel.com" <tamas@tklengyel.com>,
	"wei.liu2@citrix.com" <wei.liu2@citrix.com>,
	"jbeulich@suse.com" <jbeulich@suse.com>,
	"george.dunlap@eu.citrix.com" <george.dunlap@eu.citrix.com>,
	"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
	"Mihai Donțu" <mdontu@bitdefender.com>,
	"Andrei Vlad LUTAS" <vlutas@bitdefender.com>,
	"jun.nakajima@intel.com" <jun.nakajima@intel.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v1] x86/hvm: Generic instruction re-execution mechanism for execute faults
Date: Wed, 19 Dec 2018 16:49:43 +0000	[thread overview]
Message-ID: <516bea73-f88a-9f96-9619-fa32f9726dca@bitdefender.com> (raw)
In-Reply-To: <20181127113205.ohli6saatlwid7ua@mac>

On 27.11.2018 13:32, Roger Pau Monné wrote:
> Would it be possible to add some kind of flag to the emulator to
> signal whether p2m restrictions should be enforced/ignored?
> hvmemul_acquire_page seems like a suitable place, but I'm not that
> familiar with the emulator.
> 
> Then you could generate vm events from the emulator itself, which
> AFAICT is the only way to handle this instruction execution issue.

I've been testing what place would be the best to have the emulator send 
a event and it turns out the hvmemul_acquire_page is not ok. What worked 
form me was having the emulator send write access violations from 
hvmemul_map_linear_addr(). Here I can get the gfn, gla and offset for 
the event.

For the exec access violation I've tried to send events from 
hvmemul_insn_fetch() but there is a problem to get the same variables 
for the event. Is there a way to go around and get those params for the 
event? Any thoughts are appreciated.

Regards,
Alex
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