xen/arm: icpendr tweakreview/arm-xen-acpi-changes

> [    0.636668] armada-cp110-pinctrl f4440000.system-controller:pinctrl: registered pinctrl driver
> (XEN) d0v2: vGICD: unhandled word write 0x00000000000001 to ICPENDR8
> (XEN) traps.c:1983:d0v2 HSR=0x93810047 pc=0xffff800010545b84 gva=0xffff800010020288 gpa=0x000000f0210288
> [    0.638071] Unhandled fault at 0xffff800010020288
> [    0.638092] Mem abort info:
> [    0.638103]   ESR = 0x96000000
> [    0.638118]   EC = 0x25: DABT (current EL), IL = 32 bits
> [    0.638136]   SET = 0, FnV = 0
> [    0.638150]   EA = 0, S1PTW = 0
> [    0.638164] Data abort info:
> [    0.638178]   ISV = 0, ISS = 0x00000000
> [    0.638192]   CM = 0, WnR = 0
> [    0.638208] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000040e0b000
> [    0.638229] [ffff800010020288] pgd=000000007bfff003, pud=000000007bffe003, pmd=000000007bffd003, pte=00680000f0210707
> [    0.638268] Internal error: ttbr address size fault: 96000000 [#1] SMP
> [    0.638291] Modules linked in:
> [    0.638310] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.6.0-0.bpo.2-arm64 #1 Debian 5.6.14-2~bpo10+1
> [    0.638339] Hardware name: Marvell 8040 MACCHIATOBin (DT)
> [    0.638359] pstate: 60000085 (nZCv daIf -PAN -UAO)
> [    0.638387] pc : gic_irq_set_irqchip_state+0x54/0x90
> [    0.638408] lr : irq_set_irqchip_state+0x74/0xc0

I know this one, let me explain.

It is difficult to implement ICPENDR/ISPENDR (and also
ISACTIVER/ICACTIVER) in Xen. Currently we don't implement them at all.
In the case of writing to ICPENDR, we return error causing the
"Unhandled fault" strack trace you are seeing.

Looking at Linux mvebu_icu_irq_domain_alloc:

	/* Make sure there is no interrupt left pending by the firmware */
	err = irq_set_irqchip_state(virq, IRQCHIP_STATE_PENDING, false);
	if (err)
		goto free_msi;

In this case it would seem reasonably safe to ignore the ICPENDR request
and continue. So, please try with the appended patch for Xen. We started
ignoring writes to ICACTIVER for similar reasons. But a generic solution
requires a proper implementation of these operations.

Message-Id: <alpine.DEB.2.21.2010191039220.12247@sstabellini-ThinkPad-T480s>

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