arm64: KVM: Add Kconfig option for max VCPUs per-Guest

Current max VCPUs per-Guest is set to 4 which is preventing
us from creating a Guest (or VM) with 8 VCPUs on Host (e.g.
X-Gene Storm SOC) with 8 Host CPUs.

The correct value of max VCPUs per-Guest should be same as
the max CPUs supported by GICv2 which is 8 but, increasing
value of max VCPUs per-Guest can make things slower hence
we add Kconfig option to let KVM users select appropriate
max VCPUs per-Guest.

Signed-off-by: Anup Patel <anup.patel@linaro.org>
Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 5d85a02..0a1d697 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -26,7 +26,12 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmio.h>
 
-#define KVM_MAX_VCPUS 4
+#if defined(CONFIG_KVM_ARM_MAX_VCPUS)
+#define KVM_MAX_VCPUS CONFIG_KVM_ARM_MAX_VCPUS
+#else
+#define KVM_MAX_VCPUS 0
+#endif
+
 #define KVM_USER_MEM_SLOTS 32
 #define KVM_PRIVATE_MEM_SLOTS 4
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1

diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 4480ab3..8ba85e9 100644 (file)
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -36,6 +36,17 @@ config KVM_ARM_HOST
        ---help---
          Provides host support for ARM processors.
 
+config KVM_ARM_MAX_VCPUS
+       int "Number maximum supported virtual CPUs per VM"
+       depends on KVM_ARM_HOST
+       default 4
+       help
+         Static number of max supported virtual CPUs per VM.
+
+         If you choose a high number, the vcpu structures will be quite
+         large, so only choose a reasonable number that you expect to
+         actually use.
+
 config KVM_ARM_VGIC
        bool
        depends on KVM_ARM_HOST && OF