lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 28 May 2019 08:53:13 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: [PATCH v2 1/3] KVM: X86: Implement PV sched yield in linux guest

From: Wanpeng Li <wanpengli@...cent.com>

When sending a call-function IPI-many to vCPUs, yield if any of
the IPI target vCPUs was preempted, we just select the first
preempted target vCPU which we found since the state of target
vCPUs can change underneath and to avoid race conditions.

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 Documentation/virtual/kvm/hypercalls.txt | 11 +++++++++++
 arch/x86/include/uapi/asm/kvm_para.h     |  1 +
 arch/x86/kernel/kvm.c                    | 21 +++++++++++++++++++++
 include/uapi/linux/kvm_para.h            |  1 +
 4 files changed, 34 insertions(+)

diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
index da24c13..da21065 100644
--- a/Documentation/virtual/kvm/hypercalls.txt
+++ b/Documentation/virtual/kvm/hypercalls.txt
@@ -141,3 +141,14 @@ a0 corresponds to the APIC ID in the third argument (a2), bit 1
 corresponds to the APIC ID a2+1, and so on.
 
 Returns the number of CPUs to which the IPIs were delivered successfully.
+
+7. KVM_HC_SCHED_YIELD
+------------------------
+Architecture: x86
+Status: active
+Purpose: Hypercall used to yield if the IPI target vCPU is preempted
+
+a0: destination APIC ID
+
+Usage example: When sending a call-function IPI-many to vCPUs, yield if
+any of the IPI target vCPUs was preempted.
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 19980ec..d0bf77c 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -29,6 +29,7 @@
 #define KVM_FEATURE_PV_TLB_FLUSH	9
 #define KVM_FEATURE_ASYNC_PF_VMEXIT	10
 #define KVM_FEATURE_PV_SEND_IPI	11
+#define KVM_FEATURE_PV_SCHED_YIELD	12
 
 #define KVM_HINTS_REALTIME      0
 
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 3f0cc82..54400c2 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -540,6 +540,21 @@ static void kvm_setup_pv_ipi(void)
 	pr_info("KVM setup pv IPIs\n");
 }
 
+static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
+{
+	int cpu;
+
+	native_send_call_func_ipi(mask);
+
+	/* Make sure other vCPUs get a chance to run if they need to. */
+	for_each_cpu(cpu, mask) {
+		if (vcpu_is_preempted(cpu)) {
+			kvm_hypercall1(KVM_HC_SCHED_YIELD, per_cpu(x86_cpu_to_apicid, cpu));
+			break;
+		}
+	}
+}
+
 static void __init kvm_smp_prepare_cpus(unsigned int max_cpus)
 {
 	native_smp_prepare_cpus(max_cpus);
@@ -651,6 +666,12 @@ static void __init kvm_guest_init(void)
 #ifdef CONFIG_SMP
 	smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus;
 	smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
+	if (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) &&
+	    !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
+	    kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
+		smp_ops.send_call_func_ipi = kvm_smp_send_call_func_ipi;
+		pr_info("KVM setup pv sched yield\n");
+	}
 	if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online",
 				      kvm_cpu_online, kvm_cpu_down_prepare) < 0)
 		pr_err("kvm_guest: Failed to install cpu hotplug callbacks\n");
diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
index 6c0ce49..8b86609 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -28,6 +28,7 @@
 #define KVM_HC_MIPS_CONSOLE_OUTPUT	8
 #define KVM_HC_CLOCK_PAIRING		9
 #define KVM_HC_SEND_IPI		10
+#define KVM_HC_SCHED_YIELD		11
 
 /*
  * hypercalls use architecture specific
-- 
2.7.4

Powered by blists - more mailing lists