Hi Peter,
On 9/25/18 4:41 PM, Peter Maydell wrote:
> In commit c79c0a314c43b78 we enabled emulation of external aborts
> when the guest attempts to access a physical address with no
> mapped device. In commit 4672cbd7bed88dc6 we suppress this for
> most legacy boards to prevent breakage of previously working
> guests, but we didn't suppress it in the 'virt' board, with
> the rationale "we know that guests won't try to prod devices
> that we don't describe in the device tree or ACPI tables". This
> is mostly true, but we've had a report of a Linux guest image
> that this did break. The problem seems to be that the guest
> is (incorrectly) configured with a DEBUG_UART_PHYS value that
> tells it there is a uart at 0x10009000 (which is true for
> vexpress but not for virt), so in early bootup the kernel
> probes this bogus address.
>
> This is a misconfigured guest, so we don't need to worry
> about it too much, but we can arrange that guests that ran
> on QEMU v2.10 (before c79c0a314c43b78) will still run on
> the "virt-2.10" board model, by suppressing external aborts
> only for that version and earlier. This seems a reasonable
> compromise.
I tried another approach to keep MEMTX_DECODE_ERROR delivered (out of
0x10009000) for 2.10, using the UNIMP device, but the code looks uglier
(create too much generic code for a single issue):
-- >8 --
diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
index 4cc57a7ef6..217c9de6f6 100644
--- a/include/hw/arm/virt.h
+++ b/include/hw/arm/virt.h
@@ -101,6 +101,7 @@ typedef struct {
bool claim_edge_triggered_timers;
bool smbios_old_sys_ver;
bool no_highmem_ecam;
+ bool misconfigured_guest_debug_uart;
} VirtMachineClass;
typedef struct {
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 0b57f87abc..29bc9b9feb 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -59,6 +59,7 @@
#include "qapi/visitor.h"
#include "standard-headers/linux/input.h"
#include "hw/arm/smmuv3.h"
+#include "hw/misc/unimp.h"
#define DEFINE_VIRT_MACHINE_LATEST(major, minor, latest) \
static void virt_##major##_##minor##_class_init(ObjectClass *oc, \
@@ -1532,6 +1533,10 @@ static void machvirt_init(MachineState *machine)
fdt_add_pmu_nodes(vms);
create_uart(vms, pic, VIRT_UART, sysmem, serial_hd(0));
+ if (vmc->misconfigured_guest_debug_uart) {
+ /* kludge ... */
+ create_unimplemented_device("phantom-pl011", 0x10009000, 0x1000);
+ }
if (vms->secure) {
create_secure_ram(vms, secure_sysmem);
@@ -1924,8 +1929,11 @@ static void virt_2_10_instance_init(Object *obj)
static void virt_machine_2_10_options(MachineClass *mc)
{
+ VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc));
+
virt_machine_2_11_options(mc);
SET_MACHINE_COMPAT(mc, VIRT_COMPAT_2_10);
+ vmc->misconfigured_guest_debug_uart = true;
}
DEFINE_VIRT_MACHINE(2, 10)
--
I prefer your compromise.
>
> Cc: qemu-sta...@nongnu.org
> Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
> ---
> hw/arm/virt.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 0b57f87abcb..3ba310a37b6 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1926,6 +1926,7 @@ static void virt_machine_2_10_options(MachineClass *mc)
> {
> virt_machine_2_11_options(mc);
> SET_MACHINE_COMPAT(mc, VIRT_COMPAT_2_10);
Can you add a short comment here?
/* See https://bugs.launchpad.net/qemu/+bug/???:
* Some misconfigured Linux guest poke for vexpress uart
* at 0x10009000 */
Regardless:
Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>
> + mc->ignore_memory_transaction_failures = true;
> }
> DEFINE_VIRT_MACHINE(2, 10)
>
