linux-kernel - [PATCH 5.12 326/700] x86/hyperv: fix logical processor creation

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Date:   Mon, 12 Jul 2021 08:06:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>,
        Wei Liu <wei.liu@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 326/700] x86/hyperv: fix logical processor creation

From: Praveen Kumar <kumarpraveen@...ux.microsoft.com>

[ Upstream commit 450605c28d571eddca39a65fdbc1338add44c6d9 ]

Microsoft Hypervisor expects the logical processor index to be the same
as CPU's index during logical processor creation. Using cpu_physical_id
confuses hypervisor's scheduler. That causes the root partition not boot
when core scheduler is used.

This patch removes the call to cpu_physical_id and uses the CPU index
directly for bringing up logical processor. This scheme works for both
classic scheduler and core scheduler.

Fixes: 333abaf5abb3 (x86/hyperv: implement and use hv_smp_prepare_cpus)
Signed-off-by: Praveen Kumar <kumarpraveen@...ux.microsoft.com>
Link: https://lore.kernel.org/r/20210531074046.113452-1-kumarpraveen@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kernel/cpu/mshyperv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index e88bc296afca..a803fc423cb7 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -245,7 +245,7 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
 	for_each_present_cpu(i) {
 		if (i == 0)
 			continue;
-		ret = hv_call_add_logical_proc(numa_cpu_node(i), i, cpu_physical_id(i));
+		ret = hv_call_add_logical_proc(numa_cpu_node(i), i, i);
 		BUG_ON(ret);
 	}
 
-- 
2.30.2