Re: [Xen-devel] [PATCH] x86: restrict HVMOP_pagetable_dying to current

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.10.18 at 13:58, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 05/10/18 12:29, Jan Beulich wrote:
>> This is not used (and probably was never meant to be) by the tool stack.
>> Limiting it to the current domain in particular allows to eliminate a
>> bogus use of vCPU 0 in pagetable_dying().
>>
>> Remove the now unnecessary domain/vCPU parameters from the wrapper/hook
>> functions at the same time.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>>
>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -4895,10 +4895,12 @@ long do_hvm_op(unsigned long op, XEN_GUE
>>              return -ESRCH;
>>  
>>          rc = -EINVAL;
>> -        if ( is_hvm_domain(d) && paging_mode_shadow(d) )
>> +        if ( unlikely(d != current->domain) )
>> +            rc = -EOPNOTSUPP;
>> +        else if ( is_hvm_domain(d) && paging_mode_shadow(d) )
>>              rc = xsm_hvm_param(XSM_TARGET, d, op);
> 
> As we're switching to current-only, shouldn't this turn to XSM_HOOK ?

Not sure - I simply didn't want to fiddle with any of the semantics,
and keeping it as it is may be sub-optimal, but is certainly not going
to be wromg.

> Everything else LGTM, with one small suggestion....
> 
>>          if ( !rc )
>> -            pagetable_dying(d, a.gpa);
>> +            pagetable_dying(a.gpa);
>>  
>>          rcu_unlock_domain(d);
>>          break;
>> --- a/xen/include/asm-x86/paging.h
>> +++ b/xen/include/asm-x86/paging.h
>> @@ -345,7 +345,7 @@ void paging_write_p2m_entry(struct p2m_d
>>  
>>  /* Called from the guest to indicate that the a process is being
>>   * torn down and its pagetables will soon be discarded */
>> -void pagetable_dying(struct domain *d, paddr_t gpa);
>> +void pagetable_dying(paddr_t gpa);
> 
> Fix the comment style while in this area?

Well, I can certainly do so - I didn't because I didn't touch the
comment itself.

Jan



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