linux-kernel - [PATCH v3] KVM: x86: Add CONFIG_KVM_MAX_NR

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 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230824215244.3897419-1-kyle.meyer@hpe.com>
Date:   Thu, 24 Aug 2023 16:52:46 -0500
From:   Kyle Meyer <kyle.meyer@....com>
To:     seanjc@...gle.com, pbonzini@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...el.com,
        x86@...nel.org, hpa@...or.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, vkuznets@...hat.com,
        dmatlack@...gle.com
Cc:     russ.anderson@....com, dimitri.sivanich@....com,
        steve.wahl@....com, Kyle Meyer <kyle.meyer@....com>
Subject: [PATCH v3] KVM: x86: Add CONFIG_KVM_MAX_NR_VCPUS

Add a Kconfig entry to set the maximum number of vCPUs per KVM guest and
set the default value to 4096 when MAXSMP is enabled.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Kyle Meyer <kyle.meyer@....com>
---
v2 -> v3: Default KVM_MAX_VCPUS to 1024 when CONFIG_KVM_MAX_NR_VCPUS is not
defined. This prevents build failures in arch/x86/events/intel/core.c and
drivers/vfio/vfio_main.c when KVM is disabled.

 arch/x86/include/asm/kvm_host.h |  4 ++++
 arch/x86/kvm/Kconfig            | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3bc146dfd38d..cd27e0a00765 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -39,7 +39,11 @@
 
 #define __KVM_HAVE_ARCH_VCPU_DEBUGFS
 
+#ifdef CONFIG_KVM_MAX_NR_VCPUS
+#define KVM_MAX_VCPUS CONFIG_KVM_MAX_NR_VCPUS
+#else
 #define KVM_MAX_VCPUS 1024
+#endif
 
 /*
  * In x86, the VCPU ID corresponds to the APIC ID, and APIC IDs
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 89ca7f4c1464..e730e8255e22 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -141,4 +141,15 @@ config KVM_XEN
 config KVM_EXTERNAL_WRITE_TRACKING
 	bool
 
+config KVM_MAX_NR_VCPUS
+	int "Maximum number of vCPUs per KVM guest"
+	depends on KVM
+	range 1024 4096
+	default 4096 if MAXSMP
+	default 1024
+	help
+	  Set the maximum number of vCPUs per KVM guest. Larger values will increase
+	  the memory footprint of each KVM guest, regardless of how many vCPUs are
+	  configured.
+
 endif # VIRTUALIZATION
-- 
2.26.2