linux-kernel - [PATCH 4.20 084/183] always clear the X2APIC

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Date:   Mon, 25 Feb 2019 22:10:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Talons Lee <xin.li@...rix.com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.20 084/183] always clear the X2APIC_ENABLE bit for PV guest

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 5268c8f39e0efef81af2aaed160272d9eb507beb ]

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@...rix.com>
Reviewed-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 2f6787fc71066..c54a493e139a7 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -898,10 +898,7 @@ 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;
-- 
2.19.1