Re: [Xen-devel] Xen on Seattle

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 2 Sep 2014, Suravee Suthikulanit wrote:
> Hi all,
> 
> I am running into an issue booting Xen on Seattle platform where dom0 kernel
> failed to make the following hypercall in arch/arm/xen/enlighten.c:
> xen_percpu_init().
> 
>  HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, cpu, &info)
> 
> After investigation, the hypercall failed in the xen/common/domain.c:
> map_vcpu_info(), where it check
> 
>     if ( offset > (PAGE_SIZE - sizeof(vcpu_info_t)) )
>         return -EINVAL;
> 
> Here:
> 
> (XEN) DEBUG0: map_vcpu_info: offset = 0x6790
> (XEN) DEBUG0: map_vcpu_info: PAGE_SIZE = 0x1000
> (XEN) DEBUG0: map_vcpu_info: sizeof(vcpu_info_t) = 0x30
> 
> If I understand correctly, it seems that the hypervisor is making assumption
> that the Dom0 guest is using 4K page size.  The PAGE_SHIFT in
> include/asm-arm/config.h is currently set to 12.  So, I have tried changing
> this to 16 (for 64K page). However, there is a restriction on the 16-bit value
> of the struct active_grant_entry { length:16; }. So, I cannot boot dom0 with
> 64K page size. Is this accurate?

Hello Suravee,
yes, that is correct: all pages used in hypercalls and shared with the
hypervisor need to be 4K pages.

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