[PATCH] x86/kvm: handle the failure of __pv_cpu_mask allocation

[PATCH] x86/kvm: handle the failure of __pv_cpu_mask allocation

[Wanpeng Li]

From: Wanpeng Li <wanpengli@tencent.com>

Fallback to native ipis/tlb flush if fails to allocate __pv_cpu_mask.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
 arch/x86/kernel/kvm.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index a22deb58f86d..29d79d760996 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -46,6 +46,7 @@
 
 DEFINE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
 
+static struct apic orig_apic;
 static int kvmapf = 1;
 
 static int __init parse_no_kvmapf(char *arg)
@@ -542,6 +543,11 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
 
 static void kvm_send_ipi_mask(const struct cpumask *mask, int vector)
 {
+	if (unlikely(!this_cpu_cpumask_var_ptr(__pv_cpu_mask))) {
+		orig_apic.send_IPI_mask(mask, vector);
+		return;
+	}
+
 	__send_ipi_mask(mask, vector);
 }
 
@@ -551,6 +557,11 @@ static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
 	struct cpumask *new_mask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
 	const struct cpumask *local_mask;
 
+	if (unlikely(!new_mask)) {
+		orig_apic.send_IPI_mask_allbutself(mask, vector);
+		return;
+	}
+
 	cpumask_copy(new_mask, mask);
 	cpumask_clear_cpu(this_cpu, new_mask);
 	local_mask = new_mask;
@@ -611,6 +622,7 @@ late_initcall(setup_efi_kvm_sev_migration);
  */
 static void kvm_setup_pv_ipi(void)
 {
+	orig_apic = *apic;
 	apic->send_IPI_mask = kvm_send_ipi_mask;
 	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
 	pr_info("setup PV IPIs\n");
@@ -639,6 +651,11 @@ static void kvm_flush_tlb_multi(const struct cpumask *cpumask,
 	struct kvm_steal_time *src;
 	struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
 
+	if (unlikely(!flushmask)) {
+		native_flush_tlb_multi(cpumask, info);
+		return;
+	}
+
 	cpumask_copy(flushmask, cpumask);
 	/*
 	 * We have to call flush only on online vCPUs. And
@@ -671,11 +688,16 @@ static __init int kvm_alloc_cpumask(void)
 
 	if (pv_tlb_flush_supported() || pv_ipi_supported())
 		for_each_possible_cpu(cpu) {
-			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
-				GFP_KERNEL, cpu_to_node(cpu));
+			if (!zalloc_cpumask_var_node(&per_cpu(__pv_cpu_mask, cpu),
+				GFP_KERNEL, cpu_to_node(cpu)))
+				goto err_out;
 		}
 
 	return 0;
+err_out:
+	for_each_possible_cpu(cpu)
+		free_cpumask_var(per_cpu(__pv_cpu_mask, cpu));
+	return -ENOMEM;
 }
 arch_initcall(kvm_alloc_cpumask);
 
-- 
2.25.1

Re: [PATCH] x86/kvm: handle the failure of __pv_cpu_mask allocation

[kernel test robot]

Hi Wanpeng,

I love your patch! Perhaps something to improve:

[auto build test WARNING on kvm/master]
[also build test WARNING on tip/master linus/master linux/master v5.18-rc6 next-20220509]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/intel-lab-lkp/linux/commits/Wanpeng-Li/x86-kvm-handle-the-failure-of-__pv_cpu_mask-allocation/20220422-175106
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git master
config: i386-randconfig-a004-20220502 (https://download.01.org/0day-ci/archive/20220510/202205101754.d5Mxymtk-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.2.0-20) 11.2.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/329f0c869cf176505509f65e95e47999a9e97b3b
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Wanpeng-Li/x86-kvm-handle-the-failure-of-__pv_cpu_mask-allocation/20220422-175106
        git checkout 329f0c869cf176505509f65e95e47999a9e97b3b
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kernel/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> arch/x86/kernel/kvm.c:49:20: warning: 'orig_apic' defined but not used [-Wunused-variable]
      49 | static struct apic orig_apic;
         |                    ^~~~~~~~~


vim +/orig_apic +49 arch/x86/kernel/kvm.c

    48	
  > 49	static struct apic orig_apic;
    50	static int kvmapf = 1;
    51	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp