Support for 710 VCPUs has been tested by Red Hat since RHEL-8.4.
Increase KVM_MAX_VCPUS and KVM_SOFT_MAX_VCPUS to 710.
For reference, visible effects of changing KVM_MAX_VCPUS are:
- KVM_CAP_MAX_VCPUS and KVM_CAP_NR_VCPUS will now return 710 (of course)
- Default value for CPUID[HYPERV_CPUID_IMPLEMENT_LIMITS (00x40000005)].EAX
will now be 710
- Bitmap stack variables that will grow:
- At kvm_hv_flush_tlb() kvm_hv_send_ipi():
- Sparse VCPU bitmap (vp_bitmap) will be 96 bytes long
- vcpu_bitmap will be 92 bytes long
- vcpu_bitmap at bioapic_write_indirect() will be 92 bytes long
once patch "KVM: x86: Fix stack-out-of-bounds memory access
from ioapic_write_indirect()" is applied
Signed-off-by: Eduardo Habkost <ehabkost@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index af6ce8d4c86a..f76fae42bf45 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -37,8 +37,8 @@
#define __KVM_HAVE_ARCH_VCPU_DEBUGFS
-#define KVM_MAX_VCPUS 288
-#define KVM_SOFT_MAX_VCPUS 240
+#define KVM_MAX_VCPUS 710
+#define KVM_SOFT_MAX_VCPUS 710
#define KVM_MAX_VCPU_ID 1023
/* memory slots that are not exposed to userspace */
#define KVM_PRIVATE_MEM_SLOTS 3
--
2.31.1
