Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-27 Thread Juergen Gross
On 27/11/2018 10:24, Jan Beulich wrote: On 27.11.18 at 08:37, wrote: >> On 26/11/2018 17:50, Jan Beulich wrote: >> On 26.11.18 at 17:17, wrote: I really fail to see why it is so bad to not clobber data in a case which normally should never occur. >>> >>> See Andrew's original r

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-27 Thread Juergen Gross
On 27/11/2018 10:16, Julien Grall wrote: > Hi, > > On 11/27/18 7:34 AM, Juergen Gross wrote: >> On 26/11/2018 17:51, Julien Grall wrote: >>> >>> >>> On 26/11/2018 16:17, Juergen Gross wrote: On 26/11/2018 17:01, Julien Grall wrote: > > > On 26/11/2018 15:29, Juergen Gross wrote: >

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-27 Thread Jan Beulich
>>> On 27.11.18 at 08:37, wrote: > On 26/11/2018 17:50, Jan Beulich wrote: > On 26.11.18 at 17:17, wrote: >>> I really fail to see why it is so bad to not clobber data in a case >>> which normally should never occur. >> >> See Andrew's original reply. You're also clobbering on potential >> s

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-27 Thread Julien Grall
Hi, On 11/27/18 7:34 AM, Juergen Gross wrote: On 26/11/2018 17:51, Julien Grall wrote: On 26/11/2018 16:17, Juergen Gross wrote: On 26/11/2018 17:01, Julien Grall wrote: On 26/11/2018 15:29, Juergen Gross wrote: On 26/11/2018 15:58, Jan Beulich wrote: On 26.11.18 at 15:23, wrote: On 2

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Juergen Gross
On 26/11/2018 17:50, Jan Beulich wrote: On 26.11.18 at 17:17, wrote: >> I really fail to see why it is so bad to not clobber data in a case >> which normally should never occur. > > See Andrew's original reply. You're also clobbering on potential > success paths. I think you are missing a "

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Juergen Gross
On 26/11/2018 17:51, Julien Grall wrote: > > > On 26/11/2018 16:17, Juergen Gross wrote: >> On 26/11/2018 17:01, Julien Grall wrote: >>> >>> >>> On 26/11/2018 15:29, Juergen Gross wrote: On 26/11/2018 15:58, Jan Beulich wrote: On 26.11.18 at 15:23, wrote: >> On 26/11/2018 15:01

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Julien Grall
On 26/11/2018 16:17, Juergen Gross wrote: On 26/11/2018 17:01, Julien Grall wrote: On 26/11/2018 15:29, Juergen Gross wrote: On 26/11/2018 15:58, Jan Beulich wrote: On 26.11.18 at 15:23, wrote: On 26/11/2018 15:01, Jan Beulich wrote: On 26.11.18 at 14:52, wrote: I don't think the hype

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Jan Beulich
>>> On 26.11.18 at 17:17, wrote: > I really fail to see why it is so bad to not clobber data in a case > which normally should never occur. See Andrew's original reply. You're also clobbering on potential success paths. Jan ___ Xen-devel mailing lis

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Juergen Gross
On 26/11/2018 17:01, Julien Grall wrote: > > > On 26/11/2018 15:29, Juergen Gross wrote: >> On 26/11/2018 15:58, Jan Beulich wrote: >> On 26.11.18 at 15:23, wrote: On 26/11/2018 15:01, Jan Beulich wrote: On 26.11.18 at 14:52, wrote: >> I don't think the hypervisor should e

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Julien Grall
On 26/11/2018 15:29, Juergen Gross wrote: On 26/11/2018 15:58, Jan Beulich wrote: On 26.11.18 at 15:23, wrote: On 26/11/2018 15:01, Jan Beulich wrote: On 26.11.18 at 14:52, wrote: I don't think the hypervisor should explicitly try to make it as hard as possible for the guest to find probl

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Ian Jackson
Juergen Gross writes ("Re: [PATCH] xen: only clobber multicall elements without error"): > On 26/11/2018 15:54, Ian Jackson wrote: > > Maybe they could be clobbered losslessly ? Eg, by xoring with 0xaa or > > something. > > This would be rather hacky: I'd need to find out if clobbering was > per

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Juergen Gross
On 26/11/2018 15:58, Jan Beulich wrote: On 26.11.18 at 15:23, wrote: >> On 26/11/2018 15:01, Jan Beulich wrote: >> On 26.11.18 at 14:52, wrote: I don't think the hypervisor should explicitly try to make it as hard as possible for the guest to find problems in the code. >>> >>>

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Juergen Gross
On 26/11/2018 15:54, Ian Jackson wrote: > Jan Beulich writes ("Re: [PATCH] xen: only clobber multicall elements without > error"): >> On 23.11.18 at 14:25, wrote: >>> In debug builds the hypervisor will deliberately clobber processed >>> elements of the multicall structure. In order to ease diagn

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Jan Beulich
>>> On 26.11.18 at 15:23, wrote: > On 26/11/2018 15:01, Jan Beulich wrote: > On 26.11.18 at 14:52, wrote: >>> I don't think the hypervisor should explicitly try to make it as hard as >>> possible for the guest to find problems in the code. >> >> That's indeed not the hypervisor's goal. Inste

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Ian Jackson
Jan Beulich writes ("Re: [PATCH] xen: only clobber multicall elements without error"): > On 23.11.18 at 14:25, wrote: > > In debug builds the hypervisor will deliberately clobber processed > > elements of the multicall structure. In order to ease diagnostic data > > printout in the affected guest

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Juergen Gross
On 26/11/2018 15:01, Jan Beulich wrote: On 26.11.18 at 14:52, wrote: >> I don't think the hypervisor should explicitly try to make it as hard as >> possible for the guest to find problems in the code. > > That's indeed not the hypervisor's goal. Instead it tries to make > it as hard as possi

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Jan Beulich
>>> On 26.11.18 at 14:52, wrote: > I don't think the hypervisor should explicitly try to make it as hard as > possible for the guest to find problems in the code. That's indeed not the hypervisor's goal. Instead it tries to make it as hard as possible for the guest (developer) to make wrong assum

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Juergen Gross
On 26/11/2018 11:58, Jan Beulich wrote: On 23.11.18 at 14:25, wrote: >> In debug builds the hypervisor will deliberately clobber processed >> elements of the multicall structure. In order to ease diagnostic data >> printout in the affected guest only clobber elements which didn't >> return an

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-26 Thread Jan Beulich
>>> On 23.11.18 at 14:25, wrote: > In debug builds the hypervisor will deliberately clobber processed > elements of the multicall structure. In order to ease diagnostic data > printout in the affected guest only clobber elements which didn't > return an error. Besides what Andrew has said such a

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-23 Thread Juergen Gross
On 23/11/2018 14:28, Andrew Cooper wrote: > On 23/11/2018 13:25, Juergen Gross wrote: >> In debug builds the hypervisor will deliberately clobber processed >> elements of the multicall structure. In order to ease diagnostic data >> printout in the affected guest only clobber elements which didn't >

Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

2018-11-23 Thread Andrew Cooper
On 23/11/2018 13:25, Juergen Gross wrote: > In debug builds the hypervisor will deliberately clobber processed > elements of the multicall structure. In order to ease diagnostic data > printout in the affected guest only clobber elements which didn't > return an error. > > Signed-off-by: Juergen Gr