Re: [PATCH v6 40/60] hw/i386: add eoi_intercept_unsupported member to X86MachineState

Xiaoyao Li
2025-01-23T16:46:05Z

On 1/23/2025 8:41 PM, Igor Mammedov wrote:
> On Tue, 5 Nov 2024 01:23:48 -0500
> Xiaoyao Li <xiaoyao.li@intel.com> wrote:
>
>> Add a new bool member, eoi_intercept_unsupported, to X86MachineState
>> with default value false. Set true for TDX VM.
>
> I'd rename it to enable_eoi_intercept, by default set to true for evrything
> and make TDX override this to false.
>>
>> Inability to intercept eoi causes impossibility to emulate level
>> triggered interrupt to be re-injected when level is still kept active.
>> which affects interrupt controller emulation.
>>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> Acked-by: Gerd Hoffmann <kraxel@redhat.com>
>> ---
>> hw/i386/x86.c | 1 +
>> include/hw/i386/x86.h | 1 +
>> target/i386/kvm/tdx.c | 2 ++
>> 3 files changed, 4 insertions(+)
>>
>> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
>> index 01fc5e656272..82faeed24ff9 100644
>> --- a/hw/i386/x86.c
>> +++ b/hw/i386/x86.c
>> @@ -370,6 +370,7 @@ static void x86_machine_initfn(Object *obj)
>> x86ms->oem_table_id = g_strndup(ACPI_BUILD_APPNAME8, 8);
>> x86ms->bus_lock_ratelimit = 0;
>> x86ms->above_4g_mem_start = 4 * GiB;
>> + x86ms->eoi_intercept_unsupported = false;
>> }
>>
>> static void x86_machine_class_init(ObjectClass *oc, void *data)
>> diff --git a/include/hw/i386/x86.h b/include/hw/i386/x86.h
>> index d43cb3908e65..fd9a30391755 100644
>> --- a/include/hw/i386/x86.h
>> +++ b/include/hw/i386/x86.h
>> @@ -73,6 +73,7 @@ struct X86MachineState {
>> uint64_t above_4g_mem_start;
>>
>> /* CPU and apic information: */
>> + bool eoi_intercept_unsupported;
>> unsigned pci_irq_mask;
>> unsigned apic_id_limit;
>> uint16_t boot_cpus;
>> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
>> index 9ab4e911f78a..9dcb77e011bd 100644
>> --- a/target/i386/kvm/tdx.c
>> +++ b/target/i386/kvm/tdx.c
>> @@ -388,6 +388,8 @@ static int tdx_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
>> return -EOPNOTSUPP;
>> }
>>
>> + x86ms->eoi_intercept_unsupported = true;
>
> I don't particulary like accel go to its parent (machine) object and override things there
> and that being buried deep inside.

I would suggest don't see TDX as accel but see it as a special type of
x86 machine.

> How do you start TDX guest?
> Is there a machine property or something like it to enable TDX?

via the "confidential-guest-support" property.
This series introduces tdx-guest object and we start a TDX guest by:

$qemu-system-x86_64 -object tdx-guest,id=tdx0 \
-machine ...,confidential-guest-support=tdx0

>> +
>> /*
>> * Set kvm_readonly_mem_allowed to false, because TDX only supports readonly
>> * memory for shared memory but not for private memory. Besides, whether a
>