Re: [kvmarm] [PATCH v10 06/14] KVM: ARM: Hypervisor inititalization

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On Thu, Aug 23, 2012 at 11:08 AM, Lei Wen <adrian.wenl@xxxxxxxxx> wrote:
> Hi Christoffer,
>
> [snip]
>
>> diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S
>> index 1dc8926..4db26cb 100644
>> --- a/arch/arm/kvm/init.S
>> +++ b/arch/arm/kvm/init.S
>> @@ -15,5 +15,135 @@
>>   * along with this program; if not, write to the Free Software
>>   * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
>>   */
>> +
>> +#include <linux/linkage.h>
>> +#include <asm/unified.h>
>>  #include <asm/asm-offsets.h>
>>  #include <asm/kvm_asm.h>
>> +#include <asm/kvm_arm.h>
>> +
>> +@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
>> +@  Hypervisor initialization
>> +@    - should be called with:
>> +@        r0 = Hypervisor pgd pointer
>> +@        r1 = top of Hyp stack (kernel VA)
>> +@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
>> +       .text
>> +       .arm
>> +        .pushsection    .hyp.idmap.text,"ax"
>> +       .align 12
>> +__kvm_hyp_init:
>> +       .globl __kvm_hyp_init
>> +
>> +       @ Hyp-mode exception vector
>> +       nop
>> +       nop
>> +       nop
>> +       nop
>> +       nop
>> +       b       __do_hyp_init
>> +       nop
>> +       nop
>> +
>> +__do_hyp_init:
>> +       @ Set the sp to end of this page and push data for later use
>> +       mov     sp, pc
>> +       bic     sp, sp, #0x0ff
>> +       bic     sp, sp, #0xf00
>> +       add     sp, sp, #0x1000
>> +       push    {r0, r1, r2, r12}
>
> Is safe to use the stack here? Since our HYP memory mapping is
> gotten valid after the following HTTBR being set as I think.
>

yes, as you can see in the end of this block we have a .align 12
before __kvm_hyp_init_end giving us the stack space we need in this
page (as long as this init code doesn't grow beyond ~3K



>> +
>> +       @ Set the HTTBR to point to the hypervisor PGD pointer passed to
>> +       @ function and set the upper bits equal to the kernel PGD.
>> +       mrrc    p15, 1, r1, r2, c2
>> +       mcrr    p15, 4, r0, r2, c2
>> +
>
> [snip]
>
> Thanks,
> Lei
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