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SubjectRe: [kvmtool PATCH 21/17] kvmtool: arm: Add support for creating VM with PA size
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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.poulose@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

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