From mboxrd@z Thu Jan  1 00:00:00 1970
From: Suravee Suthikulanit <suravee.suthikulpanit@amd.com>
Subject: Re: Xen on Seattle
Date: Tue, 2 Sep 2014 13:10:19 -0500
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To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Joel Schopp <joel.schopp@amd.com>, Ian Campbell <Ian.Campbell@citrix.com>, Julien Grall <julien.grall@linaro.org>, xen-devel <xen-devel@lists.xen.org>, Stefano Stabellini <stefano.stabellini@citrix.com>, "Hurwitz,
	Sherry" <sherry.hurwitz@amd.com>
List-Id: xen-devel@lists.xenproject.org

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:
>> 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.
>

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

Suravee