linux-kernel - [RFC PATCH V2 4/4] KVM: x86: add debugfs file for lazy tscdeadline

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Message-ID: <DM6PR03MB4140849AE402EE47F94A26E6CD30A@DM6PR03MB4140.namprd03.prod.outlook.com>
Date:   Mon, 10 Jul 2023 14:03:27 +0800
From:   Wang Jianchao <jianchwa@...look.com>
To:     seanjc@...gle.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, kvm@...r.kernel.org
Cc:     arkinjob@...look.com, linux-kernel@...r.kernel.org
Subject: [RFC PATCH V2 4/4] KVM: x86: add debugfs file for lazy tscdeadline

This patch adds a file named lazy_tscdeadline, in kvm debugfs vcpu
directory to get the state. And also, if you write to it, it will
trigger a lazy_tscdeadline kick forcily which can rescue the guest
if the feature fall into bug.

Signed-off-by: Wang Jianchao <jianchwa@...look.com>
---
 arch/x86/kvm/debugfs.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 78 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
index ee8c4c3..7fb1618 100644
--- a/arch/x86/kvm/debugfs.c
+++ b/arch/x86/kvm/debugfs.c
@@ -56,6 +56,78 @@ static int vcpu_get_tsc_scaling_frac_bits(void *data, u64 *val)
 
 DEFINE_SIMPLE_ATTRIBUTE(vcpu_tsc_scaling_frac_fops, vcpu_get_tsc_scaling_frac_bits, NULL, "%llu\n");
 
+static int vcpu_lazy_tscddl_show(struct seq_file *m, void *v)
+{
+	struct kvm_vcpu *vcpu = m->private;
+
+	if (vcpu->arch.pv_cpuid.features & (1UL << KVM_FEATURE_LAZY_TSCDEADLINE)) {
+		struct kvm_host_lazy_tscdeadline *hlt = &vcpu->arch.lazy_tscdeadline;
+		if (!(hlt->msr_val & KVM_MSR_ENABLED) ||
+		    !hlt->guest)
+			seq_printf(m, "not open in guest\n");
+		else
+			seq_printf(m, "pending %llu armed %llu\n",
+					hlt->guest->pending, hlt->guest->armed);
+	} else {
+		seq_printf(m, "not enable in cpuid\n");
+	}
+
+	return 0;
+}
+
+static int vcpu_lazy_tscdeadline_open(struct inode *inode, struct file *file)
+{
+	struct kvm_vcpu *vcpu = inode->i_private;
+	struct kvm *kvm = vcpu->kvm;
+	int ret;
+
+	if (!kvm_get_kvm_safe(kvm))
+		return -ENOENT;
+
+	ret = single_open(file, vcpu_lazy_tscddl_show, vcpu);
+	if (ret < 0)
+		kvm_put_kvm(kvm);
+
+	return 0;
+}
+
+static ssize_t vcpu_lazy_tscdeadline_write(struct file *file, const char __user *buf,
+				    size_t count, loff_t *ppos)
+{
+	struct seq_file *m = file->private_data;
+	struct kvm_vcpu *vcpu = m->private;
+	struct kvm_host_lazy_tscdeadline *hlt = &vcpu->arch.lazy_tscdeadline;
+
+	if (!(hlt->msr_val & KVM_MSR_ENABLED) ||
+	    !hlt->guest)
+		goto out;
+
+	/*
+	 * Force to kick the tscdeadline timer to rescue the vcpu
+	 */
+	kvm_make_request(KVM_REQ_LAZY_TSCDEADLINE, vcpu);
+out:
+	return count;
+}
+
+static int vcpu_lazy_tscdeadline_release(struct inode *inode, struct file *file)
+{
+	struct kvm_vcpu *vcpu = inode->i_private;
+	struct kvm *kvm = vcpu->kvm;
+
+	kvm_put_kvm(kvm);
+
+	return 0;
+}
+
+static const struct file_operations vcpu_lazy_tscdeadline_fops = {
+	.open		= vcpu_lazy_tscdeadline_open,
+	.read		= seq_read,
+	.write		= vcpu_lazy_tscdeadline_write,
+	.llseek		= seq_lseek,
+	.release	= vcpu_lazy_tscdeadline_release,
+};
+
 void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry)
 {
 	debugfs_create_file("guest_mode", 0444, debugfs_dentry, vcpu,
@@ -63,11 +135,16 @@ void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_
 	debugfs_create_file("tsc-offset", 0444, debugfs_dentry, vcpu,
 			    &vcpu_tsc_offset_fops);
 
-	if (lapic_in_kernel(vcpu))
+	if (lapic_in_kernel(vcpu)) {
 		debugfs_create_file("lapic_timer_advance_ns", 0444,
 				    debugfs_dentry, vcpu,
 				    &vcpu_timer_advance_ns_fops);
 
+		debugfs_create_file("lazy_tscdeadline", 0644,
+				    debugfs_dentry, vcpu,
+				    &vcpu_lazy_tscdeadline_fops);
+	}
+
 	if (kvm_caps.has_tsc_control) {
 		debugfs_create_file("tsc-scaling-ratio", 0444,
 				    debugfs_dentry, vcpu,
-- 
2.7.4