Re: [Xen-devel] [PATCH for-4.10] xen/dom0: Fix latent dom0 construction bugs on all architectures

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/10/17 16:51, Roger Pau Monné wrote:
> On Mon, Oct 16, 2017 at 03:38:03PM +0100, Andrew Cooper wrote:
>>  * x86 PV and ARM dom0's must not clear _VPF_down from v->pause_flags until
>>    all state is actually set up.  As it currently stands, d0v0 is eligible 
>> for
>>    scheduling before its registers have been set.  This is latent as we also
>>    hold a systemcontroller pause reference at the time which prevents d0 from
>>    being scheduled.
>>
>>  * x86 PVH dom0's must set v->is_initialised on d0v0, to prevent another vcpu
>>    being able to call VCPUOP_initialise and modify state under the feet of 
>> the
>>    running vcpu.  This is latent as PVH dom0 construction don't yet function.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> LGTM, just one question.
>
>> diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
>> index e8f746c..a67071c 100644
>> --- a/xen/arch/x86/hvm/dom0_build.c
>> +++ b/xen/arch/x86/hvm/dom0_build.c
>> @@ -614,6 +614,7 @@ static int __init pvh_setup_cpus(struct domain *d, 
>> paddr_t entry,
>>  
>>      update_domain_wallclock_time(d);
>>  
>> +    v->is_initialised = 1;
>>      clear_bit(_VPF_down, &v->pause_flags);
> Don't you want to move this to the end of dom0_construct_pvh? In any
> case, at this point the vCPU state is already setup correctly.

I had considered that, but a) As you say, it only matters when the vcpu
state is set up, and b) it would look odd being anywhere later.

~Andrew

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