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From: Qian Cai <cai@lca.pw>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	rkrcmar@redhat.com, tglx@linutronix.de, mingo@redhat.com,
	bp@alien8.de, hpa@zytor.com, x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kvm: add proper frame pointer logic for vmx
Date: Tue, 15 Jan 2019 13:29:22 -0500	[thread overview]
Message-ID: <0d8d7e5a-193a-393e-6c43-899135252164@lca.pw> (raw)
In-Reply-To: <20190115174953.GC21622@linux.intel.com>



On 1/15/19 12:49 PM, Sean Christopherson wrote:
> On Tue, Jan 15, 2019 at 09:48:45AM -0800, Sean Christopherson wrote:
>> On Tue, Jan 15, 2019 at 11:43:20AM -0500, Qian Cai wrote:
>>>
>>>
>>> On 1/15/19 2:13 AM, Paolo Bonzini wrote:
>>>> Hmm, maybe like this:
>>>>
>>>> diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
>>>> index bcef2c7e9bc4..33122fa9d4bd 100644
>>>> --- a/arch/x86/kvm/vmx/vmenter.S
>>>> +++ b/arch/x86/kvm/vmx/vmenter.S
>>>> @@ -26,19 +26,17 @@ ENTRY(vmx_vmenter)
>>>>  	ret
>>>>
>>>>  2:	vmlaunch
>>>> +3:
>>>>  	ret
>>>>
>>>> -3:	cmpb $0, kvm_rebooting
>>>> -	jne 4f
>>>> -	call kvm_spurious_fault
>>>> -4:	ret
>>>> -
>>>>  	.pushsection .fixup, "ax"
>>>> -5:	jmp 3b
>>>> +4:	cmpb $0, kvm_rebooting
>>>> +	jne 3b
>>>> +	jmp kvm_spurious_fault
>>>>  	.popsection
>>>>
>>>> -	_ASM_EXTABLE(1b, 5b)
>>>> -	_ASM_EXTABLE(2b, 5b)
>>>> +	_ASM_EXTABLE(1b, 4b)
>>>> +	_ASM_EXTABLE(2b, 4b)
>>>>
>>>>  ENDPROC(vmx_vmenter)
>>>
>>> No, that will not work. The problem is in vmx.o where I just sent another patch
>>> for it.
>>>
>>> I can see there are five options to solve it.
>>>
>>> 1) always inline vmx_vcpu_run()
>>> 2) always noinline vmx_vcpu_run()
>>> 3) add -fdiable-ipa-fnsplit option to Makefile for vmx.o
>>> 4) let STACK_FRAME_NON_STANDARD support part.* syntax.
>>
>> What is ".part." and where does it come from?  Searching for information
>> is futile, the term is too generic.
> 
> And never mind, my eyes glazed over -fdiable-ipa-fnsplit.

For example, this works too,

diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index 69b3a7c30013..990dfc254e71 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -4,7 +4,7 @@ ccflags-y += -Iarch/x86/kvm

 CFLAGS_x86.o := -I.
 CFLAGS_svm.o := -I.
-CFLAGS_vmx.o := -I.
+CFLAGS_vmx.o := -I. -fdisable-tree-fnsplit

 KVM := ../../../virt/kvm


  reply	other threads:[~2019-01-15 18:29 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-15  6:44 [PATCH] kvm: add proper frame pointer logic for vmx Qian Cai
2019-01-15  7:04 ` Qian Cai
2019-01-15  7:13   ` Paolo Bonzini
2019-01-15 16:34     ` Sean Christopherson
2019-01-15 16:54       ` Qian Cai
2019-01-15 16:43     ` Qian Cai
2019-01-15 17:31       ` Qian Cai
2019-01-15 17:48       ` Sean Christopherson
2019-01-15 17:49         ` Sean Christopherson
2019-01-15 18:29           ` Qian Cai [this message]
2019-01-15 19:06       ` Sean Christopherson
2019-01-15 19:08         ` Sean Christopherson
2019-01-15 22:38         ` Josh Poimboeuf
2019-01-16  0:54           ` Sean Christopherson
2019-01-16 14:56             ` Josh Poimboeuf
2019-01-16 16:35               ` Sean Christopherson

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