Re: [kvmtool PATCH 21/17] kvmtool: arm: Add support for creating VM with PA size

[Julien Grall]

Hi Suzuki,

On 27/03/18 14:15, Suzuki K Poulose wrote:
Specify the physical size for the VM encoded in the vm type.
Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.com>
---
  arm/include/arm-common/kvm-arch.h |  6 +++++-
  arm/kvm.c                         | 21 +++++++++++++++++++++
  2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/arm/include/arm-common/kvm-arch.h 
b/arm/include/arm-common/kvm-arch.h
index ca7ab0f..64bc92a 100644
--- a/arm/include/arm-common/kvm-arch.h
+++ b/arm/include/arm-common/kvm-arch.h
@@ -42,7 +42,11 @@
  
  #define KVM_IRQ_OFFSET		GIC_SPI_IRQ_BASE
  
-#define KVM_VM_TYPE		0
+extern unsigned long           kvm_arm_type;
+extern void kvm__arch_init_hyp(struct kvm *kvm);
+
+#define KVM_VM_TYPE            kvm_arm_type
+#define kvm__arch_init_hyp     kvm__arch_init_hyp
  
  #define VIRTIO_DEFAULT_TRANS(kvm)	\
        ((kvm)->cfg.arch.virtio_trans_pci ? VIRTIO_PCI : VIRTIO_MMIO)
diff --git a/arm/kvm.c b/arm/kvm.c
index 5701d41..a9a9140 100644
--- a/arm/kvm.c
+++ b/arm/kvm.c
@@ -11,6 +11,8 @@
  #include <linux/kvm.h>
  #include <linux/sizes.h>
  
+unsigned long kvm_arm_type;
+
  struct kvm_ext kvm_req_ext[] = {
        { DEFINE_KVM_EXT(KVM_CAP_IRQCHIP) },
        { DEFINE_KVM_EXT(KVM_CAP_ONE_REG) },
@@ -18,6 +20,25 @@ struct kvm_ext kvm_req_ext[] = {
        { 0, 0 },
  };
  
+#ifndef KVM_ARM_GET_MAX_VM_PHYS_SHIFT
+#define KVM_ARM_GET_MAX_VM_PHYS_SHIFT          _IO(KVMIO, 0x0a)
+#endif

Once the IOCTL is agreed, I think you would need to update 
include/linux/kvm.h.

+
+void kvm__arch_init_hyp(struct kvm *kvm)
+{
+       unsigned max_ipa;
+
+       max_ipa = ioctl(kvm->sys_fd, KVM_ARM_GET_MAX_VM_PHYS_SHIFT);
+       if (max_ipa < 0)
+               max_ipa = 40;
+       if (!kvm->cfg.arch.phys_shift)
+               kvm->cfg.arch.phys_shift = 40;
+       if (kvm->cfg.arch.phys_shift > max_ipa)
+               die("Requested PA size (%u) is not supported by the host 
(%ubits)\n",
+                   kvm->cfg.arch.phys_shift, max_ipa);
+       kvm_arm_type = kvm->cfg.arch.phys_shift;

FWIW, older Linux will not accept a KVM type other than 0. So I think 
the best would be to bail out if KVM_ARM_GET_MAX_VM_PHYS_SHIFT does not 
exist.

For safety, you could even check that arch.phys_shift is always 40 when 
running under older Linux.

Cheers,

--
Julien Grall