Il 28/07/2014 23:36, Aurelien Jarno ha scritto:
> On Mon, Jul 28, 2014 at 12:37:50PM +0100, James Hogan wrote:
>> MIPS registers an unassigned access handler which raises a guest bus
>> error exception. However this causes QEMU to crash when KVM is enabled
>> as it isn't called from the main execution loop so longjmp() gets called
>> without a corresponding setjmp().
>>
>> Until the KVM API can be updated to trigger a guest exception in
>> response to an MMIO exit, prevent the bus error exception being raised
>> from mips_cpu_unassigned_access() if KVM is enabled.
>>
>> The check is at run time since the do_unassigned_access callback is
>> initialised before it is known whether KVM will be enabled.
>>
>> The problem can be triggered with Malta emulation by making the guest
>> write to the reset region at physical address 0x1bf00000, since it is
>> marked read-only which is treated as unassigned for writes.
>>
>> Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
>> Cc: Aurelien Jarno <aurelien@xxxxxxxxxxx>
>> Cc: Peter Maydell <peter.maydell@xxxxxxxxxx>
>> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
>> Cc: Gleb Natapov <gleb@xxxxxxxxxx>
>> Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
>> Cc: Sanjay Lal <sanjayl@xxxxxxxxxxx>
>> ---
>> target-mips/op_helper.c | 11 +++++++++++
>> 1 file changed, 11 insertions(+)
>>
>> diff --git a/target-mips/op_helper.c b/target-mips/op_helper.c
>> index 27651a4a00c1..df97b35f8701 100644
>> --- a/target-mips/op_helper.c
>> +++ b/target-mips/op_helper.c
>> @@ -21,6 +21,7 @@
>> #include "qemu/host-utils.h"
>> #include "exec/helper-proto.h"
>> #include "exec/cpu_ldst.h"
>> +#include "sysemu/kvm.h"
>>
>> #ifndef CONFIG_USER_ONLY
>> static inline void cpu_mips_tlb_flush (CPUMIPSState *env, int flush_global);
>> @@ -2168,6 +2169,16 @@ void mips_cpu_unassigned_access(CPUState *cs, hwaddr addr,
>> MIPSCPU *cpu = MIPS_CPU(cs);
>> CPUMIPSState *env = &cpu->env;
>>
>> + /*
>> + * Raising an exception with KVM enabled will crash because it won't be from
>> + * the main execution loop so the longjmp won't have a matching setjmp.
>> + * Until we can trigger a bus error exception through KVM lets just ignore
>> + * the access.
>> + */
>> + if (kvm_enabled()) {
>> + return;
>> + }
>> +
>> if (is_exec) {
>> helper_raise_exception(env, EXCP_IBE);
>> } else {
>
> Reviewed-by: Aurelien Jarno <aurelien@xxxxxxxxxxx>
>
> Note that even if the test is added for each exception, it is light
> enough compared to triggering and handling an exception so that it has
> no impact on performance.
>
> Paolo, do you want to take this patch in your kvm tree?
Sure, I'll include it for 2.2.
Paolo
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