On 22/05/2019 12:10, Jan Beulich wrote:
>>>> On 22.05.19 at 11:45, <[email protected]> wrote:
>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -3185,22 +3185,6 @@ static enum hvm_translation_result __hvm_copy(
>>
>> ASSERT(is_hvm_vcpu(v));
>>
>> - /*
>> - * XXX Disable for 4.1.0: PV-on-HVM drivers will do grant-table ops
>> - * such as query_size. Grant-table code currently does
>> copy_to/from_guest
>> - * accesses under the big per-domain lock, which this test would
>> disallow.
>> - * The test is not needed until we implement sleeping-on-waitqueue when
>> - * we access a paged-out frame, and that's post 4.1.0 now.
>> - */
>> -#if 0
>> - /*
>> - * If the required guest memory is paged out, this function may sleep.
>> - * Hence we bail immediately if called from atomic context.
>> - */
>> - if ( in_atomic() )
>> - return HVMTRANS_unhandleable;
>> -#endif
>
> Dealing with this TODO item is of course much appreciated, but
> should it really be deleted altogether? The big-domain-lock issue
> is gone afair, in which case dropping the #if 0 would seem
> possible to me, even if it's not strictly needed without the sleep-
> on-waitqueue behavior mentioned.
I just had a look and found the following path:
do_domctl() (takes domctl_lock and hypercall_deadlock_mutex)
arch_do_domctl()
raw_copy_from_guest()
copy_from_user_hvm()
hvm_copy_from_guest_linear()
__hvm_copy()
So no, we can't do the in_atomic() test IMO.
Juergen
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