Re: [Xen-devel] [PATCH v2 ] always clear the X2APIC_ENABLE bit for PV guest

Re: [Xen-devel] [PATCH v2 ] always clear the X2APIC_ENABLE bit for PV guest

[Boris Ostrovsky]

On 1/14/19 7:43 AM, Igor Druzhinin wrote:
> ping?

Applied to for-linus-4.21 (nka 5.0)

(this should have been copied to linux-kernel@vger.kernel.org and to me,
which is partly the reason why it was missed)

-boris


>
> On 10/12/2018 10:03, Xin Li wrote:
>> From: Talons Lee <xin.li@citrix.com>
>>
>> Commit e657fcc clears cpu capability bit instead of using fake cpuid
>> value, the EXTD should always be off for PV guest without depending
>> on cpuid value. So remove the cpuid check in xen_read_msr_safe() to
>> always clear the X2APIC_ENABLE bit.
>>
>> Signed-off-by: Talons Lee <xin.li@citrix.com>
>> Reviewed-by: Juergen Gross <jgross@suse.com>
>>
>> ---
>> CC: Igor Druzhinin <igor.druzhinin@citrix.com>
>> CC: Sergey Dyasli <sergey.dyasli@citrix.com>
>> CC: Andrew Cooper <andrew.cooper3@citrix.com>
>> CC: Juergen Gross <jgross@suse.com>
>>
>> v2:
>> don't use fake cpuid to cheat xen_read_msr_safe(), just always clear
>> the EXTD bit.
>> ---
>>  arch/x86/xen/enlighten_pv.c | 5 +----
>>  1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
>> index 4b20082..17cf92b 100644
>> --- a/arch/x86/xen/enlighten_pv.c
>> +++ b/arch/x86/xen/enlighten_pv.c
>> @@ -900,10 +900,7 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err)
>>  	val = native_read_msr_safe(msr, err);
>>  	switch (msr) {
>>  	case MSR_IA32_APICBASE:
>> -#ifdef CONFIG_X86_X2APIC
>> -		if (!(cpuid_ecx(1) & (1 << (X86_FEATURE_X2APIC & 31))))
>> -#endif
>> -			val &= ~X2APIC_ENABLE;
>> +		val &= ~X2APIC_ENABLE;
>>  		break;
>>  	}
>>  	return val;
>>
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