On 17 September 2018 at 11:41, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
@@ -122,6 +122,14 @@ the default trap & emulate implementation (which changes the virtual
memory layout to fit in user mode), check KVM_CAP_MIPS_VZ and use the
+To configure the physical address space size for a VM (IPA size) on arm64,
+check KVM_CAP_ARM_VM_PHYS_SHIFT (which returns the maximum limit for the
+IPA shift) and use KVM_VM_TYPE_ARM_PHYS_SHIFT(PHYS_SHIFT). Bits[7-0] of the
+machine type has been reserved for specifying the PHYS_SHIFT.
+The supported range is [32...IPA_LIMIT], where IPA_LIMIT could be
+identified by checking KVM_CAP_ARM_VM_PHYS_SHIFT. For backward compatibility
+a value of 0 selects 40bits.
Given this as the API documentation, I don't think I could figure out
what I as a userspace user of it need to do without looking at the
kernel code. Could I ask you to expand it so that it is a bit less
terse and a bit more detailed? (For instance, what is a PHYS_SHIFT
and why do I have to specify it rather than just telling the kernel
I want a 48 bit guest address space?)