[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xen-devel] [PATCH linux v3 3/9] xen: introduce xen_vcpu_id mapping
- To: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Julien Grall <julien.grall@xxxxxxx>
- Date: Wed, 7 Sep 2016 10:35:19 +0100
- Cc: Juergen Gross <jgross@xxxxxxxx>, Wei Chen <Wei.Chen@xxxxxxx>, Steve Capper <Steve.Capper@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Kaly Xin <Kaly.Xin@xxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, David Vrabel <david.vrabel@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>
- Delivery-date: Wed, 07 Sep 2016 09:35:32 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
Hi Vitaly,
On 07/09/2016 10:07, Vitaly Kuznetsov wrote:
Stefano Stabellini <sstabellini@xxxxxxxxxx> writes:
I don't know that much about cpuid, but the virtual MPIDR is constructed
from the vcpu id right now:
v->arch.vmpidr = MPIDR_SMP | vcpuid_to_vaffinity(v->vcpu_id);
[...]
static inline register_t vcpuid_to_vaffinity(unsigned int vcpuid)
{
register_t vaff;
vaff = (vcpuid & 0x0f) << MPIDR_LEVEL_SHIFT(0);
vaff |= ((vcpuid >> 4) & MPIDR_LEVEL_MASK) << MPIDR_LEVEL_SHIFT(1);
return vaff;
}
This could work but only in case there is a way to get MPIDR for _other_
cpu (e.g. CPU0 needs to get MPIDR of CPU1 when CPU1 is not yet runnning)
or we'll have to change the machinery of how we bring up secondary CPUs
- e.g. CPUn starts, writes its id somewhere and 'hangs' waiting for CPU0
to set up event channels.
You can get the MPIDR from both the device tree and ACPI. The firmware
table is parsed at boot time and the value is stored in cpu_logical_map().
Regards,
--
Julien Grall
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel
|
