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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: "M. Vefa Bicakci" <m.v.b@runbox.com>, linux-kernel@vger.kernel.org
Cc: Dominik Brodowski <linux@dominikbrodowski.net>,
	Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Juergen Gross <jgross@suse.com>,
	xen-devel@lists.xenproject.org, x86@kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH 1/2] x86/entry/64: Do not clear %rbx under Xen
Date: Mon, 23 Jul 2018 10:56:28 -0400	[thread overview]
Message-ID: <15aa906e-0e42-31ce-f3d3-167d263e9226@oracle.com> (raw)
In-Reply-To: <6426e7a4-2da0-9a36-298a-89e956e98812@runbox.com>

On 07/21/2018 07:18 PM, M. Vefa Bicakci wrote:
> On 07/21/2018 05:19 PM, Boris Ostrovsky wrote:
>> On 07/21/2018 03:49 PM, M. Vefa Bicakci wrote:
>>> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
>>> index c7449f377a77..96e8ff34129e 100644
>>> --- a/arch/x86/entry/entry_64.S
>>> +++ b/arch/x86/entry/entry_64.S
>>> @@ -1129,7 +1129,7 @@ ENTRY(xen_failsafe_callback)
>>>       addq    $0x30, %rsp
>>>       UNWIND_HINT_IRET_REGS
>>>       pushq    $-1 /* orig_ax = -1 => not a system call */
>>> -    PUSH_AND_CLEAR_REGS
>>> +    PUSH_AND_CLEAR_REGS clear_rbx=0
>>
>>
>> Do we need this at all? We are returning from the hypervisor here.
>>
>> -boris
>>
>>>       ENCODE_FRAME_POINTER
>>>       jmp    error_exit
>>>   END(xen_failsafe_callback)
>
> Hello Boris,
>
> If you are referring to the PUSH_AND_CLEAR_REGS macro itself, I am not
> sure;
> however, not clearing the RBX register seemed to resolve the issues
> mentioned
> in the commit message for me. Given Andy's comment though, I believe
> that the
> approach in this patch may not be correct.


I was only referring to register clearing part of PUSH_AND_CLEAR_REGS.


-boris



  reply	other threads:[~2018-07-23 14:56 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-21 19:49 [PATCH 1/2] x86/entry/64: Do not clear %rbx under Xen M. Vefa Bicakci
2018-07-21 19:49 ` [PATCH 2/2] xen/pv: Call get_cpu_address_sizes to set x86_virt/phys_bits M. Vefa Bicakci
2018-07-21 21:25   ` Boris Ostrovsky
2018-07-21 23:17     ` M. Vefa Bicakci
2018-07-22 15:57       ` M. Vefa Bicakci
2018-07-23 15:04         ` Boris Ostrovsky
2018-07-24 12:42           ` M. Vefa Bicakci
2018-07-24 12:45   ` [PATCH v2] " M. Vefa Bicakci
2018-07-24 14:08     ` Boris Ostrovsky
2018-07-26  3:56     ` [PATCH v3] " M. Vefa Bicakci
2018-08-06 20:15     ` [PATCH v2] " Boris Ostrovsky
2018-08-06 20:16       ` Thomas Gleixner
2018-08-06 21:27         ` Boris Ostrovsky
2018-08-07  9:50       ` Ingo Molnar
2018-07-21 21:19 ` [PATCH 1/2] x86/entry/64: Do not clear %rbx under Xen Boris Ostrovsky
2018-07-21 23:18   ` M. Vefa Bicakci
2018-07-23 14:56     ` Boris Ostrovsky [this message]
2018-07-21 21:45 ` Andy Lutomirski
2018-07-21 23:19   ` M. Vefa Bicakci
2018-07-21 23:30     ` Andy Lutomirski
2018-07-21 23:37       ` M. Vefa Bicakci
2018-07-22  1:20         ` M. Vefa Bicakci
2018-07-22 17:56           ` Andy Lutomirski
2018-07-22 18:32             ` [Xen-devel] " Andrew Cooper

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