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

From: Pavel Fedin
Subject: Re: [Qemu-devel] [PATCH] Use Aff1 with mpidr
Date: Fri, 29 May 2015 09:45:14 +0300


> I see that you added mpidr to ARMCpu and initialized it in virt.c then you 
> use it in
> Thus you must fix all other virtual machines in hw/arm not just virt.c as it 
> is not
initialized for
> them.

 The only change in virt.c is:
--- cut ---
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index a7f9a10..a1186c5 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -317,7 +317,11 @@ static void fdt_add_cpu_nodes(const VirtBoardInfo *vbi)
                                         "enable-method", "psci");
-        qemu_fdt_setprop_cell(vbi->fdt, nodename, "reg", cpu);
+        /*
+         * If cpus node's #address-cells property is set to 1
+         * The reg cell bits [23:0] must be set to bits [23:0] of MPIDR_EL1.
+         */
+        qemu_fdt_setprop_cell(vbi->fdt, nodename, "reg", armcpu->mpidr);
--- cut ---
 So that it takes MPIDR instead of just CPU index. Theoretically - yes, may be 
machines should also be changed, but:
1. They are 32-bit, so MPIDR == index for them, because there are no more than 
8 CPUs.
2. Those machines AFAIK do not compose device tree by themselves. They use 
pre-made ones
instead, coming for example with kernel.
 Only virt currently can be a 64-bit machine and cares about more than 8 CPUs.
 As to MPIDR initialization, it is done in arm_cpu_initfn(), therefore all ARM 
CPUs get
this automatically. There's no need to modify code for every machine.
 I would kindly ask you to use my patch in your next series, or base something 
on it, if
you dislike the implementation, but it's crucial for KVM that MPIDR values can 
be obtained
from the host. Your original implementation cannot do this by design, this is 
why i made
my own solution. See kvm_arch_init_vcpu() in my patch - without this CPUs 
beyond #7 will
not power up in KVM.
 And when are you planning to post v3? I am waiting for it to be integrated, in 
order to
add KVM vGICv3. Otherwise i'm afraid there are too many collisions.

Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia

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