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From: Marc Zyngier <maz@kernel.org>
To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: Andre Przywara <Andre.Przywara@arm.com>,
	Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH][kvmtool] kvm: Request VM specific limits instead of system-wide ones
Date: Mon, 27 Apr 2020 15:17:38 +0100	[thread overview]
Message-ID: <20200427141738.285217-1-maz@kernel.org> (raw)

On arm64, the maximum number of vcpus is constrained by the type
of interrupt controller that has been selected (GICv2 imposes a
limit of 8 vcpus, while GICv3 currently has a limit of 512).

It is thus important to request this limit on the VM file descriptor
rather than on the one that corresponds to /dev/kvm, as the latter
is likely to return something that doesn't take the constraints into
account.

Reported-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 kvm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kvm.c b/kvm.c
index e327541..3d5173d 100644
--- a/kvm.c
+++ b/kvm.c
@@ -406,7 +406,7 @@ int kvm__recommended_cpus(struct kvm *kvm)
 {
 	int ret;
 
-	ret = ioctl(kvm->sys_fd, KVM_CHECK_EXTENSION, KVM_CAP_NR_VCPUS);
+	ret = ioctl(kvm->vm_fd, KVM_CHECK_EXTENSION, KVM_CAP_NR_VCPUS);
 	if (ret <= 0)
 		/*
 		 * api.txt states that if KVM_CAP_NR_VCPUS does not exist,
@@ -421,7 +421,7 @@ int kvm__max_cpus(struct kvm *kvm)
 {
 	int ret;
 
-	ret = ioctl(kvm->sys_fd, KVM_CHECK_EXTENSION, KVM_CAP_MAX_VCPUS);
+	ret = ioctl(kvm->vm_fd, KVM_CHECK_EXTENSION, KVM_CAP_MAX_VCPUS);
 	if (ret <= 0)
 		ret = kvm__recommended_cpus(kvm);
 
-- 
2.26.2

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WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Will Deacon <will@kernel.org>,
	Andre Przywara <Andre.Przywara@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH][kvmtool] kvm: Request VM specific limits instead of system-wide ones
Date: Mon, 27 Apr 2020 15:17:38 +0100	[thread overview]
Message-ID: <20200427141738.285217-1-maz@kernel.org> (raw)

On arm64, the maximum number of vcpus is constrained by the type
of interrupt controller that has been selected (GICv2 imposes a
limit of 8 vcpus, while GICv3 currently has a limit of 512).

It is thus important to request this limit on the VM file descriptor
rather than on the one that corresponds to /dev/kvm, as the latter
is likely to return something that doesn't take the constraints into
account.

Reported-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 kvm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kvm.c b/kvm.c
index e327541..3d5173d 100644
--- a/kvm.c
+++ b/kvm.c
@@ -406,7 +406,7 @@ int kvm__recommended_cpus(struct kvm *kvm)
 {
 	int ret;
 
-	ret = ioctl(kvm->sys_fd, KVM_CHECK_EXTENSION, KVM_CAP_NR_VCPUS);
+	ret = ioctl(kvm->vm_fd, KVM_CHECK_EXTENSION, KVM_CAP_NR_VCPUS);
 	if (ret <= 0)
 		/*
 		 * api.txt states that if KVM_CAP_NR_VCPUS does not exist,
@@ -421,7 +421,7 @@ int kvm__max_cpus(struct kvm *kvm)
 {
 	int ret;
 
-	ret = ioctl(kvm->sys_fd, KVM_CHECK_EXTENSION, KVM_CAP_MAX_VCPUS);
+	ret = ioctl(kvm->vm_fd, KVM_CHECK_EXTENSION, KVM_CAP_MAX_VCPUS);
 	if (ret <= 0)
 		ret = kvm__recommended_cpus(kvm);
 
-- 
2.26.2


             reply	other threads:[~2020-04-27 14:17 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-27 14:17 Marc Zyngier [this message]
2020-04-27 14:17 ` [PATCH][kvmtool] kvm: Request VM specific limits instead of system-wide ones Marc Zyngier
2020-04-27 14:44 ` Alexandru Elisei
2020-04-27 14:44   ` Alexandru Elisei
2020-04-27 15:00   ` Alexandru Elisei
2020-04-27 15:00     ` Alexandru Elisei
2020-04-27 17:33     ` Marc Zyngier
2020-04-27 17:33       ` Marc Zyngier
2020-04-28  9:09       ` Alexandru Elisei
2020-04-28  9:09         ` Alexandru Elisei
2020-04-27 15:37 ` André Przywara
2020-04-27 15:37   ` André Przywara
2020-04-27 16:49   ` Marc Zyngier
2020-04-27 16:49     ` Marc Zyngier

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