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Re: [Xen-devel] Xen on Seattle

On 9/2/2014 1:06 PM, Stefano Stabellini wrote:
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:

  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;


(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.

Ok, the next question would be, would it make sense/possible to extend the support to allow 64K pages?


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