linux-kernel - [PATCH 1/2] x86/xen: Allow to retry if cpu_initialize

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Message-Id: <20211206152034.2150770-2-bigeasy@linutronix.de>
Date:   Mon,  6 Dec 2021 16:20:33 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org, x86@...nel.org,
        xen-devel@...ts.xenproject.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Longpeng <longpeng2@...wei.com>,
        Gonglei <arei.gonglei@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 1/2] x86/xen: Allow to retry if cpu_initialize_context() failed.

From: Boris Ostrovsky <boris.ostrovsky@...cle.com>

If memory allocation in cpu_initialize_context() fails then it will
bring up the VCPU and leave with the corresponding CPU bit set in
xen_cpu_initialized_map.
The following (presumably successful) CPU bring up will BUG in
xen_pv_cpu_up() because nothing for that VCPU would be initialized.

Clear the CPU bits, that were set in cpu_initialize_context() in case
the memory allocation fails.

[ bigeasy: Creating a patch from Boris' email. ]

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 arch/x86/xen/smp_pv.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
index 6a8f3b53ab834..86368fcef4667 100644
--- a/arch/x86/xen/smp_pv.c
+++ b/arch/x86/xen/smp_pv.c
@@ -277,8 +277,11 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 		return 0;
 
 	ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
-	if (ctxt == NULL)
+	if (ctxt == NULL) {
+		cpumask_clear_cpu(cpu, xen_cpu_initialized_map);
+		cpumask_clear_cpu(cpu, cpu_callout_mask);
 		return -ENOMEM;
+	}
 
 	gdt = get_cpu_gdt_rw(cpu);
 
-- 
2.34.1