Re: [Xen-devel] [PATCH] x86/domain: Drop the only-written smap_check_policy infrastructure

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/05/18 17:10, Roger Pau Monné wrote:
> On Tue, May 08, 2018 at 02:03:04PM +0100, Andrew Cooper wrote:
>> c/s 4c5d78a10d "x86/pagewalk: Re-implement the pagetable walker" dropped the
>> consumer of smap_policy.  Looking at c/s 31ae587e6f which introduced the
>> smap_check logic, it exists only to work around a bug in guest_walk_tables()
>> was resolved by the aformentioned commit.
>>
>> Remove the unused variables and associated infrastructure.
>>
>> Reported-by: Jason Andryuk <jandryuk@xxxxxxxxx>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>
>> diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
>> index 8b66096..197f8d6 100644
>> --- a/xen/include/asm-x86/domain.h
>> +++ b/xen/include/asm-x86/domain.h
>> @@ -595,7 +583,6 @@ struct arch_vcpu
>>  
>>  struct guest_memory_policy
>>  {
>> -    smap_check_policy_t smap_policy;
>>      bool nested_guest_mode;
> Maybe guest_memory_policy could be dropped and
> update_guest_memory_policy updated to take a bool nested_mode
> parameter? 

update_guest_memory_policy() stores the old value in the passed
structure, and would more accurately be toggle_guest_memory_policy()
when it came to guest mode.

> Or the function can be dropped altogether likely.

Sadly not yet.  This exists because of Xen's virtual-address based API
for the shared info and time mappings.  This API is bad and wrong and
wants fixing.  ISTR Juergen and Julien having plans to deal with this?

~Andrew

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