summaryrefslogtreecommitdiff
path: root/Documentation/virtual
diff options
context:
space:
mode:
authorSuzuki K Poulose <suzuki.poulose@arm.com>2018-09-26 19:32:54 +0300
committerMarc Zyngier <marc.zyngier@arm.com>2018-10-03 13:45:20 +0300
commit233a7cb235318223df8133235383f4c595c654c1 (patch)
tree04f9ed017c9cf6463f7bcf95801b8e070da0b7ef /Documentation/virtual
parent58b3efc820acd3219e89ff014e93346a734229b8 (diff)
downloadlinux-233a7cb235318223df8133235383f4c595c654c1.tar.xz
kvm: arm64: Allow tuning the physical address size for VM
Allow specifying the physical address size limit for a new VM via the kvm_type argument for the KVM_CREATE_VM ioctl. This allows us to finalise the stage2 page table as early as possible and hence perform the right checks on the memory slots without complication. The size is encoded as Log2(PA_Size) in bits[7:0] of the type field. For backward compatibility the value 0 is reserved and implies 40bits. Also, lift the limit of the IPA to host limit and allow lower IPA sizes (e.g, 32). The userspace could check the extension KVM_CAP_ARM_VM_IPA_SIZE for the availability of this feature. The cap check returns the maximum limit for the physical address shift supported by the host. Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Christoffer Dall <cdall@kernel.org> Cc: Peter Maydell <peter.maydell@linaro.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/api.txt31
1 files changed, 31 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 647f94128a85..f6b0af55d010 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -123,6 +123,37 @@ memory layout to fit in user mode), check KVM_CAP_MIPS_VZ and use the
flag KVM_VM_MIPS_VZ.
+On arm64, the physical address size for a VM (IPA Size limit) is limited
+to 40bits by default. The limit can be configured if the host supports the
+extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
+KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type
+identifier, where IPA_Bits is the maximum width of any physical
+address used by the VM. The IPA_Bits is encoded in bits[7-0] of the
+machine type identifier.
+
+e.g, to configure a guest to use 48bit physical address size :
+
+ vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48));
+
+The requested size (IPA_Bits) must be :
+ 0 - Implies default size, 40bits (for backward compatibility)
+
+ or
+
+ N - Implies N bits, where N is a positive integer such that,
+ 32 <= N <= Host_IPA_Limit
+
+Host_IPA_Limit is the maximum possible value for IPA_Bits on the host and
+is dependent on the CPU capability and the kernel configuration. The limit can
+be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION
+ioctl() at run-time.
+
+Please note that configuring the IPA size does not affect the capability
+exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects
+size of the address translated by the stage2 level (guest physical to
+host physical address translations).
+
+
4.3 KVM_GET_MSR_INDEX_LIST, KVM_GET_MSR_FEATURE_INDEX_LIST
Capability: basic, KVM_CAP_GET_MSR_FEATURES for KVM_GET_MSR_FEATURE_INDEX_LIST