From: Pekka Enberg <penberg@kernel.org>
Date: Sat, 7 May 2011 14:37:28 +0000 (+0300)
Subject: kvm tools: Limit CPU count by KVM_CAP_NR_VCPUS
X-Git-Tag: next-20110824~3^2~345
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=b1ecfb588f366ac4b5118ed020170e71c5247486;p=karo-tx-linux.git

kvm tools: Limit CPU count by KVM_CAP_NR_VCPUS

This patch limits the number of CPUs to KVM_CAP_NR_VCPUS when user specifies
more CPUs with the "--cpus=N" command line option than what the in-kernel KVM
is able to handle.

Cc: Asias He <asias.hejun@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Prasad Joshi <prasadjoshi124@gmail.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
---

diff --git a/tools/kvm/include/kvm/kvm.h b/tools/kvm/include/kvm/kvm.h
index f6975794985d..3dab78de4fae 100644
--- a/tools/kvm/include/kvm/kvm.h
+++ b/tools/kvm/include/kvm/kvm.h
@@ -29,6 +29,7 @@ struct kvm {
 };
 
 struct kvm *kvm__init(const char *kvm_dev, unsigned long ram_size);
+int kvm__max_cpus(struct kvm *self);
 void kvm__init_ram(struct kvm *self);
 void kvm__delete(struct kvm *self);
 bool kvm__load_kernel(struct kvm *kvm, const char *kernel_filename,
diff --git a/tools/kvm/kvm-run.c b/tools/kvm/kvm-run.c
index 2504ab02a85e..ec1e4621649e 100644
--- a/tools/kvm/kvm-run.c
+++ b/tools/kvm/kvm-run.c
@@ -311,11 +311,12 @@ static char *host_image(char *cmd_line, size_t size)
 int kvm_cmd_run(int argc, const char **argv, const char *prefix)
 {
 	static char real_cmdline[2048];
+	unsigned int nr_online_cpus;
+	int max_cpus;
 	int exit_code = 0;
 	int i;
 	struct virtio_net_parameters net_params;
 	char *hi;
-	unsigned int nr_online_cpus;
 
 	signal(SIGALRM, handle_sigalrm);
 	signal(SIGQUIT, handle_sigquit);
@@ -383,6 +384,13 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
 
 	kvm = kvm__init(kvm_dev, ram_size);
 
+	max_cpus = kvm__max_cpus(kvm);
+
+	if (nrcpus > max_cpus) {
+		printf("  # Limit the number of CPUs to %d\n", max_cpus);
+		kvm->nrcpus	= max_cpus;
+	}
+
 	kvm->nrcpus = nrcpus;
 
 	memset(real_cmdline, 0, sizeof(real_cmdline));
diff --git a/tools/kvm/kvm.c b/tools/kvm/kvm.c
index b3adb6b2ce3e..65793f24df7f 100644
--- a/tools/kvm/kvm.c
+++ b/tools/kvm/kvm.c
@@ -170,6 +170,17 @@ void kvm__init_ram(struct kvm *self)
 		die_perror("KVM_SET_USER_MEMORY_REGION ioctl");
 }
 
+int kvm__max_cpus(struct kvm *self)
+{
+	int ret;
+
+	ret = ioctl(self->sys_fd, KVM_CHECK_EXTENSION, KVM_CAP_NR_VCPUS);
+	if (ret < 0)
+		die_perror("KVM_CAP_NR_VCPUS");
+
+	return ret;
+}
+
 struct kvm *kvm__init(const char *kvm_dev, unsigned long ram_size)
 {
 	struct kvm_pit_config pit_config = { .flags = 0, };