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From: Pavel Fedin <p.fedin@samsung.com>
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Date: Wed, 29 Jul 2015 17:01:53 +0300
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Subject: Re: [Qemu-devel] [PATCH v3] hw/arm/virt: Add high MMIO PCI region
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To: 'Peter Maydell' <peter.maydell@linaro.org>
Cc: 'Igor Mammedov' <imammedo@redhat.com>, 'Alexander Graf' <agraf@suse.de>, "'Michael S. Tsirkin'" <mst@redhat.com>, 'QEMU Developers' <qemu-devel@nongnu.org>, 'Paolo Bonzini' <pbonzini@redhat.com>

 Hello! I have studied the problem. It is a kernel bug and it's still =
not fixed, at least in 4.1

> (1) We should confirm whether this really is a guest kernel
> bug (as opposed to the device tree QEMU emits not being
> in spec)

 The problem is in of_pci_range_to_resource(): =
http://lxr.free-electrons.com/source/drivers/of/address.c#L313
 Note the line 333: res->start =3D range->cpu_addr; here is the problem. =
The problem occurs if CONFIG_ARM_LPAE is disabled. Inside struct =
resource 'start' and 'end' are of  resource_size_t type, which is an =
alias of phys_addr_t:
--- cut ---
#ifdef CONFIG_PHYS_ADDR_T_64BIT
typedef u64 phys_addr_t;
#else
typedef u32 phys_addr_t;
#endif

typedef phys_addr_t resource_size_t;
--- cut ---
 Config option chain is as follows: CONFIG_ARM_LPAE =3D> =
CONFIG_ARCH_PHYS_ADDR_T_64BIT =3D> CONFIG_PHYS_ADDR_T_64BIT
 This function should check that range->cpu_addr fits into 32 bits if =
LPAE is disabled.

> (2) If it is a kernel bug, submit a patch to fix it

 Will do it.

> (3) Consider a workaround for older guests anyway. The
> scope of that workaround would depend on exactly which
> guests are affected, which is presumably something we
> figured out during step (1).

 Problem occurs if LPAE is disabled in the kernel. What is your verdict =
then? Do we need an option or just ignore those poor guys with such old =
configs?

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