Re: [Xen-devel] [PATCH v2 1/7] x86: slightly reduce Meltdown band-aid overhead

2018-03-02 Thread Andrew Cooper
On 02/03/18 11:34, Jan Beulich wrote: On 01.03.18 at 20:21, wrote: >> On 08/02/18 09:20, Jan Beulich wrote: >> On 07.02.18 at 20:35, wrote: On 07/02/18 16:12, Jan Beulich wrote: > I'm not sure why I didn't do this right away: By avoiding the use of > global PTEs in the clone

Re: [Xen-devel] [PATCH v2 1/7] x86: slightly reduce Meltdown band-aid overhead

2018-03-02 Thread Jan Beulich
>>> On 01.03.18 at 20:21, wrote: > On 08/02/18 09:20, Jan Beulich wrote: > On 07.02.18 at 20:35, wrote: >>> On 07/02/18 16:12, Jan Beulich wrote: I'm not sure why I didn't do this right away: By avoiding the use of global PTEs in the cloned directmap, there's no need to fiddle with

Re: [Xen-devel] [PATCH v2 1/7] x86: slightly reduce Meltdown band-aid overhead

2018-03-01 Thread Andrew Cooper
On 08/02/18 09:20, Jan Beulich wrote: On 07.02.18 at 20:35, wrote: >> On 07/02/18 16:12, Jan Beulich wrote: >>> I'm not sure why I didn't do this right away: By avoiding the use of >>> global PTEs in the cloned directmap, there's no need to fiddle with >>> CR4.PGE on any of the entry paths. O

Re: [Xen-devel] [PATCH v2 1/7] x86: slightly reduce Meltdown band-aid overhead

2018-02-08 Thread Jan Beulich
>>> On 07.02.18 at 20:35, wrote: > On 07/02/18 16:12, Jan Beulich wrote: >> I'm not sure why I didn't do this right away: By avoiding the use of >> global PTEs in the cloned directmap, there's no need to fiddle with >> CR4.PGE on any of the entry paths. Only the exit paths need to flush >> global

Re: [Xen-devel] [PATCH v2 1/7] x86: slightly reduce Meltdown band-aid overhead

2018-02-07 Thread Andrew Cooper
On 07/02/18 16:12, Jan Beulich wrote: > I'm not sure why I didn't do this right away: By avoiding the use of > global PTEs in the cloned directmap, there's no need to fiddle with > CR4.PGE on any of the entry paths. Only the exit paths need to flush > global mappings. > > The reduced flushing, howe

[Xen-devel] [PATCH v2 1/7] x86: slightly reduce Meltdown band-aid overhead

2018-02-07 Thread Jan Beulich
I'm not sure why I didn't do this right away: By avoiding the use of global PTEs in the cloned directmap, there's no need to fiddle with CR4.PGE on any of the entry paths. Only the exit paths need to flush global mappings. The reduced flushing, however, implies that we now need to have interrupts