Re: [Xen-devel] [PATCH v3 13/16] xen/arm: Add support for GIC v3

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 04/23/2014 06:01 PM, Ian Campbell wrote:
>> +    } while ( count-- );
>> +
>> +    if ( !count )
>> +        dprintk(XENLOG_WARNING, "RWP timeout\n");
> 
> Shouldn't we panic here?

I don't think panic is the solution here. This might be use on secondary
CPU.

IHMO, we should return an error code here an handle here upper in the
call stack.

>> +static void gicv3_restore_state(struct vcpu *v)
>> +{
>> +    int i;
>> +
>> +    for ( i = 0; i < nr_lrs; i++)
>> +        gich_write_lr(i, v->arch.gic.v3.lr[i]);
> 
> I wonder if the compiler could do a better job of this using the same
> switch and fallthrough method you used for aprn regs?

Marc has written a very nice solution for this stuff. It as written an
assembly function where all registers is save decreasing the number.

When the function, it will calculate the number of regs we don't need of
LRs save. This will avoid lots of jumps.

See code below (see http://permalink.gmane.org
/gmane.linux.ports.arm.kernel/310855 for the whole patch):

+       sub     w23, w23, w22   // How many regs we have to skip
+
+       adr     x24, 1f
+       add     x24, x24, x23, lsl #2
+       br      x24
+
+1:
+       mrs     x20, ICH_LR15_EL2
+       mrs     x19, ICH_LR14_EL2
+       mrs     x18, ICH_LR13_EL2
+       mrs     x17, ICH_LR12_EL2
+       mrs     x16, ICH_LR11_EL2
+       mrs     x15, ICH_LR10_EL2
+       mrs     x14, ICH_LR9_EL2
+       mrs     x13, ICH_LR8_EL2
+       mrs     x12, ICH_LR7_EL2
+       mrs     x11, ICH_LR6_EL2
+       mrs     x10, ICH_LR5_EL2
+       mrs     x9, ICH_LR4_EL2
+       mrs     x8, ICH_LR3_EL2
+       mrs     x7, ICH_LR2_EL2
+       mrs     x6, ICH_LR1_EL2
+       mrs     x5, ICH_LR0_EL2
+

[..]

>> +                return 0;
> 
> So basically we only know the number of redistributors from device tree
> and not the mapping from RDIST to CPU, so we have to try every one?
> 
> Do you have a reference to the GIC v3 Device Tree bindings? I don't see
> them in linux/Documentation/devicetree/bindings/.

GICv3 is not upstream for now. Marc as sent the V3 recently:

http://comments.gmane.org/gmane.linux.ports.arm.kernel/316902

-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel