From: Julien Grall <julien.grall@arm.com>
To: Jan Beulich <JBeulich@suse.com>, Chao Gao <chao.gao@intel.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>, xen-devel@lists.xen.org
Subject: Re: [PATCH v3] x86/vlapic: Don't reset APIC ID when handling INIT signal
Date: Thu, 20 Apr 2017 16:39:06 +0100 [thread overview]
Message-ID: <54c35f99-13f3-4db8-f6b4-3539648aa964@arm.com> (raw)
In-Reply-To: <58F8D5060200007800152742@prv-mh.provo.novell.com>
Hi,
On 20/04/17 14:34, Jan Beulich wrote:
>>>> On 19.04.17 at 22:22, <chao.gao@intel.com> wrote:
>> According to SDM "ADVANCED PROGRAMMABLE INTERRUPT CONTROLLER (APIC) ->
>> "EXTENDED XAPIC (X2APIC)" -> "x2APIC State Transitions", the APIC mode
>> and APIC ID are preserved when handling INIT signal and a reset places
>> APIC to xAPIC mode and APIC base address to 0xFEE00000h (this part
>> is in "Local APIC" -> "Local APIC Status and Location"). So there are
>> two problems in current code:
>> 1. Using reset logic (aka vlapic_reset) to handle INIT signal.
>> 2. Forgetting resetting APIC mode and base address in vlapic_reset()
>>
>> This patch introduces a new function vlapic_do_init() and replaces the
>> wrongly used vlapic_reset(). Also reset APIC mode and APIC base address
>> in vlapic_reset().
>>
>> Note that: LDR is read only in x2APIC mode. Resetting it to zero in x2APIC
>> mode is unreasonable. This patch also doesn't reset LDR when handling INIT
>> signal in x2APIC mode.
>>
>> Signed-off-by: Chao Gao <chao.gao@intel.com>
>
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
>
>> I regard this patch as a bug fix. But I haven't seen issues caused by
>> this bug and am not sure of the existance of such issues. Anyhow Cc
>> Julien and leave the decision to you (Julien and Jan).
>
> Julien,
>
> I'm slightly in favor of taking it now, but I won't object if you decide
> otherwise.
Chao, can you assess the benefits/risks of having this patch in Xen 4.9?
Cheers,
--
Julien Grall
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next prev parent reply other threads:[~2017-04-20 15:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 20:22 [PATCH v3] x86/vlapic: Don't reset APIC ID when handling INIT signal Chao Gao
2017-04-20 13:34 ` Jan Beulich
2017-04-20 6:59 ` Chao Gao
2017-04-20 14:15 ` Jan Beulich
2017-04-20 7:37 ` Chao Gao
2017-04-20 15:05 ` Jan Beulich
2017-04-20 15:39 ` Julien Grall [this message]
2017-04-20 9:25 ` Chao Gao
2017-04-21 9:45 ` Julien Grall
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