On Fri, 22 Jun 2018 at 14:09, Peter Maydell <peter.mayd...@linaro.org> wrote:
>
> From: Eric Auger <eric.au...@redhat.com>
>
> With this patch, virt-3.0 machine uses a new 256MB ECAM region
> by default instead of the legacy 16MB one, if highmem is set
> (LPAE supported by the guest) and (!firmware_loaded || aarch64).
>
> Indeed aarch32 mode FW may not support this high ECAM region.
This is a rather old change by now, but I've been looking
at it because it exposes an issue which was previously
masked by a different bug...
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index d8abf89e8c8..0f8bfa57d7e 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1318,6 +1318,7 @@ static void machvirt_init(MachineState *machine)
> int n, virt_max_cpus;
> MemoryRegion *ram = g_new(MemoryRegion, 1);
> bool firmware_loaded = bios_name || drive_get(IF_PFLASH, 0, 0);
> + bool aarch64 = true;
>
> /* We can probe only here because during property set
> * KVM is not available yet
> @@ -1433,6 +1434,8 @@ static void machvirt_init(MachineState *machine)
> numa_cpu_pre_plug(&possible_cpus->cpus[cs->cpu_index],
> DEVICE(cpuobj),
> &error_fatal);
>
> + aarch64 &= object_property_get_bool(cpuobj, "aarch64", NULL);
> +
> if (!vms->secure) {
> object_property_set_bool(cpuobj, false, "has_el3", NULL);
> }
> @@ -1491,6 +1494,8 @@ static void machvirt_init(MachineState *machine)
> create_uart(vms, pic, VIRT_SECURE_UART, secure_sysmem, serial_hd(1));
> }
>
> + vms->highmem_ecam &= vms->highmem && (!firmware_loaded || aarch64);
Do you remember why this conditional is the way it is?
As it stands, it will disable the high-memory ECAM for
an AArch32 VM that's loaded firmware, but leaves it enabled
if we're direct booting Linux. That's a problem because 32-bit
Linux falls over if you pass it a highmem-ECAM, even if LPAE
is enabled (somewhere along the line it discards the high 32
bits of the address of the ECAM in the dtb, so it thinks the
ECAM overlaps with another memory region, and won't recognize
the pci controller; I have a feeling this is a regression in
the kernel). Plus, we have no way to tell if the guest
kernel has LPAE enabled at all.
Maybe it would be safer to insist that the guest is aarch64
before we enable highmem ECAM?
thanks
-- PMM
