Re: [Xen-devel] [PATCH v4 02/12] livepatch: Allow to override inter-modules buildid dependency

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.09.2019 13:14,  Wieczorkiewicz, Pawel  wrote:
> 
> 
>> On 30. Sep 2019, at 13:05, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>
>> On 28.09.2019 17:12, Pawel Wieczorkiewicz wrote:
>>> --- a/xen/include/public/sysctl.h
>>> +++ b/xen/include/public/sysctl.h
>>> @@ -35,7 +35,7 @@
>>> #include "domctl.h"
>>> #include "physdev.h"
>>>
>>> -#define XEN_SYSCTL_INTERFACE_VERSION 0x00000012
>>> +#define XEN_SYSCTL_INTERFACE_VERSION 0x00000013
>>
>> Oh, I see.
>>
>>> @@ -956,6 +956,15 @@ struct xen_sysctl_livepatch_action {
>>>                                             /* hypervisor default. */
>>>                                             /* Or upper bound of time (ns) 
>>> */
>>>                                             /* for operation to take. */
>>> +
>>> +/*
>>> + * Overwrite default inter-module buildid dependency chain enforcement.
>>> + * Check only if module is built for given hypervisor by comparing buildid.
>>> + */
>>> +#define LIVEPATCH_ACTION_APPLY_NODEPS (1 << 0)
>>> +    uint64_t flags;                         /* IN: action flags. */
>>> +                                            /* Provide additional 
>>> parameters */
>>> +                                            /* for an action. */
>>
>> 64 bits seems quite a lot (and unusual) for a flags field. Also,
> 
> When I use uint32_t for the flags, I would have to also add another
> one for padding I suppose.
> Why not just use that space for future flags? So, I chose uint64_t.

uint64_t is (on x86 and 32-bit architectures at least) less efficient
to deal with.

Jan

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