Re: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-10 Thread Thomas Gleixner
On Wed, 10 Jan 2018, Borislav Petkov wrote: > On Wed, Jan 10, 2018 at 07:20:13AM +0100, Ingo Molnar wrote: > > it be really unreasonable to say that if a microcode update changes CPU > > flags an initrd rebuild and a reboot is required? It's not like microcode > > updates > > are _that_ frequent

Re: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-10 Thread Borislav Petkov
On Wed, Jan 10, 2018 at 07:20:13AM +0100, Ingo Molnar wrote: > it be really unreasonable to say that if a microcode update changes CPU > flags an initrd rebuild and a reboot is required? It's not like microcode > updates > are _that_ frequent - in fact they tend to be much _less_ frequent in a

Re: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-10 Thread Thomas Gleixner
On Tue, 9 Jan 2018, Andy Lutomirski wrote: > > On Jan 9, 2018, at 5:47 PM, Thomas Gleixner wrote: > > > > On Wed, 10 Jan 2018, Van De Ven, Arjan wrote: > >>> In other words, if you use late microcode loading for getting IBRS, you > >>> don't get ALTERNATIVE patching and its benefits? > >>> > >>>

Re: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-09 Thread Ingo Molnar
* Dave Hansen wrote: > On 01/09/2018 05:06 PM, Thomas Gleixner wrote: > > This is for the case where we need to set feature flags late, like, for > > example, after late microcode patch has been loaded which has enabled > > new CPUID bits. > > > > This has no effect on alternatives patching. >

Re: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-09 Thread Andy Lutomirski
> On Jan 9, 2018, at 5:47 PM, Thomas Gleixner wrote: > > On Wed, 10 Jan 2018, Van De Ven, Arjan wrote: >>> In other words, if you use late microcode loading for getting IBRS, you >>> don't get ALTERNATIVE patching and its benefits? >>> >>> I'll also profess some microcode ignorance here. Is "l

RE: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-09 Thread Thomas Gleixner
On Wed, 10 Jan 2018, Van De Ven, Arjan wrote: > > In other words, if you use late microcode loading for getting IBRS, you > > don't get ALTERNATIVE patching and its benefits? > > > > I'll also profess some microcode ignorance here. Is "late microcode > > patching" *all* of the stuff we do from th

Re: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-09 Thread Thomas Gleixner
On Tue, 9 Jan 2018, Dave Hansen wrote: > On 01/09/2018 05:06 PM, Thomas Gleixner wrote: > > This is for the case where we need to set feature flags late, like, for > > example, after late microcode patch has been loaded which has enabled > > new CPUID bits. > > > > This has no effect on alternati

RE: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-09 Thread Van De Ven, Arjan
> In other words, if you use late microcode loading for getting IBRS, you > don't get ALTERNATIVE patching and its benefits? > > I'll also profess some microcode ignorance here. Is "late microcode > patching" *all* of the stuff we do from the OS, or do we have early and > late Linux loading in

Re: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

2018-01-09 Thread Dave Hansen
On 01/09/2018 05:06 PM, Thomas Gleixner wrote: > This is for the case where we need to set feature flags late, like, for > example, after late microcode patch has been loaded which has enabled > new CPUID bits. > > This has no effect on alternatives patching. In other words, if you use late micro