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Re: [Qemu-devel] [PATCH] Use Aff1 with mpidr

From: Shannon Zhao
Subject: Re: [Qemu-devel] [PATCH] Use Aff1 with mpidr
Date: Sat, 30 May 2015 10:30:33 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.4.0

On 2015/5/30 1:37, Pavel Fedin wrote:
>  Hi!
>> Well KVM side should be fixed instead of driving us along wrong route.
>  I have studied the question a bit more, and i discovered that MPIDR access 
> on ARM is not
> trapped by KVM. And guest would always get the same value as host would. 
> Theoretically you

Yes, it doesn't trap but there is one register "vmpidr_el2" which is
used for virtualization. When guest reads mpidr, it will get the value
of vmpidr_el2. And when context switching, hyp will restore the value of
vmpidr_el2 and the value is got from MPIDR_EL1 which is set by


.macro restore_sysregs // x2: base address for cpu context
        // x3: tmp register
        add     x3, x2, #CPU_SYSREG_OFFSET(MPIDR_EL1)
        msr     vmpidr_el2,     x4


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