Increase KVM_MAX_VCPUS to 1024, so we can test larger VMs.
I'm not changing KVM_SOFT_MAX_VCPUS yet because I'm afraid it
might involve complicated questions around the meaning of
"supported" and "recommended" in the upstream tree.
KVM_SOFT_MAX_VCPUS will be changed in a separate patch.
For reference, visible effects of this change are:
- KVM_CAP_MAX_VCPUS will now return 1024 (of course)
- Default value for CPUID[HYPERV_CPUID_IMPLEMENT_LIMITS (00x40000005)].EAX
will now be 1024
- KVM_MAX_VCPU_ID will change from 1151 to 4096
- Size of struct kvm will increase from 19328 to 22272 bytes
(in x86_64)
- Size of struct kvm_ioapic will increase from 1780 to 5084 bytes
(in x86_64)
- Bitmap stack variables that will grow:
- At kvm_hv_flush_tlb() kvm_hv_send_ipi(),
vp_bitmap[] and vcpu_bitmap[] will now be 128 bytes long
- vcpu_bitmap at bioapic_write_indirect() will be 128 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>
---
Note: this conflicts with:
https://lore.kernel.org/lkml/20210903130808.30142-7-jgross@xxxxxxxx
Date: Fri, 3 Sep 2021 15:08:07 +0200
From: Juergen Gross <jgross@xxxxxxxx>
Subject: [PATCH v2 6/6] x86/kvm: add boot parameter for setting max number of vcpus per
guest
Message-Id: <20210903130808.30142-7-jgross@xxxxxxxx>
I don't intend this to block Juergen's work. If Juergen's series is merged
first, I can redo this patch to change KVM_DEFAULT_MAX_VCPUS instead.
---
arch/x86/include/asm/kvm_host.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f4cbc08b8d4d..e30e40399092 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -37,7 +37,7 @@
#define __KVM_HAVE_ARCH_VCPU_DEBUGFS
-#define KVM_MAX_VCPUS 288
+#define KVM_MAX_VCPUS 1024
#define KVM_SOFT_MAX_VCPUS 240
/*
--
2.31.1
