From: Corneliu ZUZU <czuzu@bitdefender.com>
To: Julien Grall <julien.grall@arm.com>,
Tamas K Lengyel <tamas.k.lengyel@gmail.com>
Cc: Wei Liu <wei.liu2@citrix.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Keir Fraser <keir@xen.org>,
Razvan Cojocaru <rcojocaru@bitdefender.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
Jan Beulich <jbeulich@suse.com>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] vm_event: Implement ARM SMC events
Date: Wed, 13 Apr 2016 14:02:27 +0300 [thread overview]
Message-ID: <570E2743.9020006@bitdefender.com> (raw)
In-Reply-To: <570E24E6.8030207@arm.com>
On 4/13/2016 1:52 PM, Julien Grall wrote:
> Hello Corneliu,
>
> On 13/04/16 09:55, Corneliu ZUZU wrote:
>> On 4/12/2016 8:24 PM, Tamas K Lengyel wrote:
>> Another issue came to my mind: "HVC #imm", if handled through the
>> hvm-ops code, currently requires setting other registers to predefined
>> values before the HVC is actually issued. That would imply additional
>> effort to save/restore those registers if an external privileged domain
>> would want to set guest breakpoints. Given that, if we were to use HVC
>> for sw-bkpts, IMO it would be nice if the hvm-ops code architecture
>> would be slightly changed such that -lone- "HVM #imm" calls would be
>> achievable for some use cases, such as this.
>
> That is not true. All the hypercalls are using the same #imm
> (XEN_HYPERCALL_TAG = 0xEA1), which indeed requires specific value in
> various registers to differentiate the HVM-ops.
>
> It's up to us to define the requirements for the other #imm. For
> instance there are some #imm allocated for debugging (see
> do_debug_trap) that will dump the content of the registers.
>
That's nice, I wonder why we didn't do that for guest-request vm-events...
>>
>>>
>>> So what I will do instead of issuing a software_breakpoint vm_event
>>> for SMCs, I'll introduce a new type, say
>>> VM_EVENT_REASON_PRIVILEGED_CALL, that can be used to forward both
>>> hypercalls and SMCs to a monitoring guest. This would also allow us to
>>> use the software_breakpoint type for the actual software breakpoint
>>> events in the future.
>>>
>>> Tamas
>>
>> Isn't the HVC-part already achieved by guest-request vm-events? Maybe
>> tying this vm-event specifically to SMC (in which case the name could be
>> something like VM_EVENT_REASON_SECURE_CALL) and thus making it
>> ARM-specific would avoid that redundancy?
>
> I would create 2 distinct events for HVC and SMC. It would make easier
> to differentiate them in userspace.
>
> Regards,
>
As stated, HVC events are already implemented as guest-request vm-events
(hence the redundancy that a VM_EVENT_REASON_PRIVILEGED_CALL would add).
So indeed, that would leave us with the option of simply creating
another event for SMC.
Corneliu.
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next prev parent reply other threads:[~2016-04-13 11:02 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-11 19:47 [PATCH] vm_event: Implement ARM SMC events Tamas K Lengyel
2016-04-12 4:31 ` Jan Beulich
2016-04-12 5:35 ` Razvan Cojocaru
2016-04-12 15:08 ` Tamas K Lengyel
2016-04-12 15:05 ` Tamas K Lengyel
2016-04-12 15:58 ` Julien Grall
2016-04-12 17:58 ` Tamas K Lengyel
2016-04-12 7:51 ` Corneliu ZUZU
2016-04-12 15:01 ` Tamas K Lengyel
2016-04-12 16:24 ` Julien Grall
2016-04-12 17:05 ` Corneliu ZUZU
2016-04-12 17:24 ` Tamas K Lengyel
2016-04-13 8:55 ` Corneliu ZUZU
2016-04-13 10:17 ` Andrew Cooper
2016-04-13 10:53 ` Corneliu ZUZU
2016-04-13 12:02 ` Andrew Cooper
2016-04-13 13:25 ` Tamas K Lengyel
2016-04-13 15:06 ` Lars Kurth
2016-04-13 15:13 ` Tamas K Lengyel
2016-04-13 10:52 ` Julien Grall
2016-04-13 11:02 ` Corneliu ZUZU [this message]
2016-04-13 15:32 ` Tamas K Lengyel
2016-04-12 14:55 ` Konrad Rzeszutek Wilk
2016-04-12 15:22 ` Tamas K Lengyel
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