BACKPORT: UPSTREAM: KVM: Raise the maximum number of user memslots
Current KVM_USER_MEM_SLOTS limits are arch specific (512 on Power, 509 on x86,
32 on s390, 16 on MIPS) but they don't really need to be. Memory slots are
allocated dynamically in KVM when added so the only real limitation is
'id_to_index' array which is 'short'. We don't have any other
KVM_MEM_SLOTS_NUM/KVM_USER_MEM_SLOTS-sized statically defined structures.
Low KVM_USER_MEM_SLOTS can be a limiting factor for some configurations.
In particular, when QEMU tries to start a Windows guest with Hyper-V SynIC
enabled and e.g. 256 vCPUs the limit is hit as SynIC requires two pages per
vCPU and the guest is free to pick any GFN for each of them, this fragments
memslots as QEMU wants to have a separate memslot for each of these pages
(which are supposed to act as 'overlay' pages).
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210127175731.2020089-3-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry-picked from commit 4fc096a99e01dd06dc55bef76ade7f8d76653245)
Conflicts:
arch/mips/include/asm/kvm_host.h - kept original KVM_MAX_VCPUS 8
instead of patch's 16 from v5.x kernel.
BUG=b:219086168
BUG=b:207515789
TEST=emerge chromeos-kernel-4_19
Change-Id: Ic67c513c43f1a9c7d2fd19b2168d9f41c9e56af4
Signed-off-by: Ryan Neph <ryanneph@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3620960
Reviewed-by: Yiwei Zhang <zzyiwei@chromium.org>
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 7e1b19e..2c063fff 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -34,7 +34,6 @@
#define __KVM_HAVE_ARCH_INTC_INITIALIZED
-#define KVM_USER_MEM_SLOTS 512
#define KVM_HALT_POLL_NS_DEFAULT 500000
#include <kvm/arm_vgic.h>
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index c254761..1310e60 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -79,7 +79,6 @@
#define KVM_MAX_VCPUS 8
-#define KVM_USER_MEM_SLOTS 8
/* memory slots that does not exposed to userspace */
#define KVM_PRIVATE_MEM_SLOTS 0
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 7b54d84..63a4ba6 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -39,7 +39,6 @@
#define KVM_MAX_VCPUS NR_CPUS
#define KVM_MAX_VCORES NR_CPUS
-#define KVM_USER_MEM_SLOTS 512
#include <asm/cputhreads.h>
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index be8fa30..9795602 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -27,7 +27,6 @@
#define KVM_S390_BSCA_CPU_SLOTS 64
#define KVM_S390_ESCA_CPU_SLOTS 248
#define KVM_MAX_VCPUS 255
-#define KVM_USER_MEM_SLOTS 32
/*
* These seem to be used for allocating ->chip in the routing table, which we
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c909ea1..480ccd5d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -40,10 +40,8 @@
#define KVM_MAX_VCPUS 288
#define KVM_SOFT_MAX_VCPUS 240
#define KVM_MAX_VCPU_ID 1023
-#define KVM_USER_MEM_SLOTS 509
/* memory slots that are not exposed to userspace */
#define KVM_PRIVATE_MEM_SLOTS 3
-#define KVM_MEM_SLOTS_NUM (KVM_USER_MEM_SLOTS + KVM_PRIVATE_MEM_SLOTS)
#define KVM_HALT_POLL_NS_DEFAULT 200000
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 09fabe5..91d6be6 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -404,9 +404,8 @@
#define KVM_PRIVATE_MEM_SLOTS 0
#endif
-#ifndef KVM_MEM_SLOTS_NUM
-#define KVM_MEM_SLOTS_NUM (KVM_USER_MEM_SLOTS + KVM_PRIVATE_MEM_SLOTS)
-#endif
+#define KVM_MEM_SLOTS_NUM SHRT_MAX
+#define KVM_USER_MEM_SLOTS (KVM_MEM_SLOTS_NUM - KVM_PRIVATE_MEM_SLOTS)
#ifndef __KVM_VCPU_MULTIPLE_ADDRESS_SPACE
static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
