Re: [RFC PATCH v2 16/22] i386/xen: handle VCPUOP_register_vcpu_info

[Paul Durrant <xadimgnik@gmail.com>]

On 13/12/2022 00:13, David Woodhouse wrote:
> On Mon, 2022-12-12 at 14:58 +0000, Paul Durrant wrote:
>> On 09/12/2022 09:56, David Woodhouse wrote:
>>> From: Joao Martins <
>>> joao.m.martins@oracle.com
>>>>
>>>
>>> Handle the hypercall to set a per vcpu info, and also wire up the
>>> default
>>> vcpu_info in the shared_info page for the first 32 vCPUs.
>>>
>>> To avoid deadlock within KVM a vCPU thread must set its *own*
>>> vcpu_info
>>> rather than it being set from the context in which the hypercall is
>>> invoked.
>>>
>>> Add the vcpu_info (and default) GPA to the vmstate_x86_cpu for
>>> migration,
>>> and restore it in kvm_arch_put_registers() appropriately.
>>>
>>> Signed-off-by: Joao Martins <
>>> joao.m.martins@oracle.com
>>>>
>>> Signed-off-by: David Woodhouse <
>>> dwmw@amazon.co.uk
>>>>
>>> ---
>>>    target/i386/cpu.h        |  2 ++
>>>    target/i386/kvm/kvm.c    | 19 +++++++++++
>>>    target/i386/machine.c    | 21 ++++++++++++
>>>    target/i386/trace-events |  1 +
>>>    target/i386/xen.c        | 74
>>> +++++++++++++++++++++++++++++++++++++---
>>>    target/i386/xen.h        |  1 +
>>>    6 files changed, 113 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
>>> index c6c57baed5..109b2e5669 100644
>>> --- a/target/i386/cpu.h
>>> +++ b/target/i386/cpu.h
>>> @@ -1788,6 +1788,8 @@ typedef struct CPUArchState {
>>>    #endif
>>>    #if defined(CONFIG_KVM)
>>>        struct kvm_nested_state *nested_state;
>>> +    uint64_t xen_vcpu_info_gpa;
>>> +    uint64_t xen_vcpu_info_default_gpa;
>>>    #endif
>>>    #if defined(CONFIG_HVF)
>>>        HVFX86LazyFlags hvf_lflags;
>>> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
>>> index ebde6bc204..fa45e2f99a 100644
>>> --- a/target/i386/kvm/kvm.c
>>> +++ b/target/i386/kvm/kvm.c
>>> @@ -1811,6 +1811,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
>>>            has_msr_hv_hypercall = true;
>>>        }
>>>    
>>> +    env->xen_vcpu_info_gpa = UINT64_MAX;
>>> +    env->xen_vcpu_info_default_gpa = UINT64_MAX;
>>
>>
>> There was an INVALID_GPA definition for shared info. Looks like we
>> could use it here too.
> 
> There was, and I started trying to use it, but it fell foul of the "is
> this going to live in target/ or hw/ and who can include what from
> where?" and I decided to just use UINT64_MAX for now and keep typing.
> 
> That will work out in the end, I'm sure.

Hopefully 
https://lore.kernel.org/lkml/20221209023622.274715-1-yu.c.zhang@linux.intel.com/ 
will help.

> 
>> Some sanity checks wouldn't go a miss here...
>>
>> rvi.offset should:
>> a) be < TARGET_PAGE_SIZE, and
>> b) ba aligned to vcpu_info_t size
> 
> Ack.