Igor Mammedov <imammedo@xxxxxxxxxx> writes:
> On Wed, 08 Jul 2015 18:42:01 -0400
> Bandan Das <bsd@xxxxxxxxxx> wrote:
>
>>
>> If a Linux guest is assigned more memory than is supported
>> by the host processor, the guest is unable to boot. That
>> is expected, however, there's no message indicating the user
>> what went wrong. This change prints a message to stderr if
>> KVM has the corresponding capability.
>>
>> Reported-by: Laszlo Ersek <lersek@xxxxxxxxxx>
>> Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
>> ---
>> linux-headers/linux/kvm.h | 1 +
>> target-i386/kvm.c | 6 ++++++
>> 2 files changed, 7 insertions(+)
>>
>> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
>> index 3bac873..6afad49 100644
>> --- a/linux-headers/linux/kvm.h
>> +++ b/linux-headers/linux/kvm.h
>> @@ -817,6 +817,7 @@ struct kvm_ppc_smmu_info {
>> #define KVM_CAP_DISABLE_QUIRKS 116
>> #define KVM_CAP_X86_SMM 117
>> #define KVM_CAP_MULTI_ADDRESS_SPACE 118
>> +#define KVM_CAP_PHY_ADDR_WIDTH 119
>>
>> #ifdef KVM_CAP_IRQ_ROUTING
>>
>> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
>> index 066d03d..66e3448 100644
>> --- a/target-i386/kvm.c
>> +++ b/target-i386/kvm.c
>> @@ -892,6 +892,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>> uint64_t shadow_mem;
>> int ret;
>> struct utsname utsname;
>> + int max_phys_bits;
>>
>> ret = kvm_get_supported_msrs(s);
>> if (ret < 0) {
>> @@ -945,6 +946,11 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>> }
>> }
>>
>> + max_phys_bits = kvm_check_extension(s, KVM_CAP_PHY_ADDR_WIDTH);
> max_phys_bits seems generic enough and could be applied to other targets
> as well.
I am a little clueless about other targets but is figuring this out from userspace
as simple as it's on x86 (cpuid)? If not, then I agree, this could be made a generic
value.
Bandan
> making it a property of machine, would make accessing/manipulating it easier.
> define default value for machine/TCG mode and when KVM is enabled
> it would override/set its own limit.
>
> then any board could easily access machine->max_gpa to make board specific
> checks.
>
>> + if (max_phys_bits && (1ULL << max_phys_bits) <= ram_size)
>> + fprintf(stderr, "Warning: The amount of memory assigned to the guest "
>> + "is more than that supported by the host CPU(s). Guest may be unstable.\n");
>> +
>> if (kvm_check_extension(s, KVM_CAP_X86_SMM)) {
>> smram_machine_done.notify = register_smram_listener;
>> qemu_add_machine_init_done_notifier(&smram_machine_done);
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