Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, 2018-01-27 at 08:59 -0500, Konrad Rzeszutek Wilk wrote: > On Mon, Jan 08, 2018 at 05:14:37PM +0100, Peter Zijlstra wrote: > > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > > > > > > > > > > a good suggestion, but we encountered some issues with it either > > >

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, 2018-01-27 at 08:59 -0500, Konrad Rzeszutek Wilk wrote: > On Mon, Jan 08, 2018 at 05:14:37PM +0100, Peter Zijlstra wrote: > > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > > > > > > > > > > a good suggestion, but we encountered some issues with it either > > >

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, Jan 08, 2018 at 05:14:37PM +0100, Peter Zijlstra wrote: > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > > a good suggestion, but we encountered some issues with it either > > > crashing the kernel at boot or not properly turning on/off. > > The below boots, but I

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, Jan 08, 2018 at 05:14:37PM +0100, Peter Zijlstra wrote: > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > > a good suggestion, but we encountered some issues with it either > > > crashing the kernel at boot or not properly turning on/off. > > The below boots, but I

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/09/2018 10:13 AM, David Woodhouse wrote: > On Tue, 2018-01-09 at 09:55 -0800, Tim Chen wrote: >> >> Thomas, >> >> I'll be sending an updated patchset with boot option opt in for ibrs >> and leave the control varaible out. I agree that we can worry about the >> control variable later. > >

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/09/2018 10:13 AM, David Woodhouse wrote: > On Tue, 2018-01-09 at 09:55 -0800, Tim Chen wrote: >> >> Thomas, >> >> I'll be sending an updated patchset with boot option opt in for ibrs >> and leave the control varaible out. I agree that we can worry about the >> control variable later. > >

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Tue, 2018-01-09 at 09:55 -0800, Tim Chen wrote: > > Thomas, > > I'll be sending an updated patchset with boot option opt in for ibrs > and leave the control varaible out.  I agree that we can worry about the > control variable later. Please base this on the spectre_v2= option that's already

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Tue, 2018-01-09 at 09:55 -0800, Tim Chen wrote: > > Thomas, > > I'll be sending an updated patchset with boot option opt in for ibrs > and leave the control varaible out.  I agree that we can worry about the > control variable later. Please base this on the spectre_v2= option that's already

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/08/2018 04:29 PM, Borislav Petkov wrote: > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: >> From: Tim Chen >> From: Andrea Arcangeli > > There's Co-Developed-by for this: > > - Co-Developed-by: states that the patch was also

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/08/2018 04:29 PM, Borislav Petkov wrote: > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: >> From: Tim Chen >> From: Andrea Arcangeli > > There's Co-Developed-by for this: > > - Co-Developed-by: states that the patch was also created by another > developer >along with

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/09/2018 02:40 AM, Thomas Gleixner wrote: > On Mon, 8 Jan 2018, Peter Zijlstra wrote: >> On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: >>> On 01/08/2018 08:14 AM, Peter Zijlstra wrote: On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: >> a good suggestion,

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/09/2018 02:40 AM, Thomas Gleixner wrote: > On Mon, 8 Jan 2018, Peter Zijlstra wrote: >> On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: >>> On 01/08/2018 08:14 AM, Peter Zijlstra wrote: On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: >> a good suggestion,

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, 8 Jan 2018, Peter Zijlstra wrote: > On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: > > On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > >>> a good suggestion, but we encountered some issues with it either > >

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, 8 Jan 2018, Peter Zijlstra wrote: > On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: > > On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > >>> a good suggestion, but we encountered some issues with it either > >

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > From: Tim Chen > From: Andrea Arcangeli There's Co-Developed-by for this: - Co-Developed-by: states that the patch was also created by another developer along with the original

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > From: Tim Chen > From: Andrea Arcangeli There's Co-Developed-by for this: - Co-Developed-by: states that the patch was also created by another developer along with the original author. This is useful at times when multiple

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> > On Mon, 2018-01-08 at 18:42 +0100, Peter Zijlstra wrote: > > On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: > > > On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > > >>> a good suggestion, but we encountered

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> > On Mon, 2018-01-08 at 18:42 +0100, Peter Zijlstra wrote: > > On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: > > > On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > > >>> a good suggestion, but we encountered

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, 2018-01-08 at 18:42 +0100, Peter Zijlstra wrote: > On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: > > On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > >>> a good suggestion, but we encountered some issues

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, 2018-01-08 at 18:42 +0100, Peter Zijlstra wrote: > On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: > > On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > >>> a good suggestion, but we encountered some issues

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, Jan 08, 2018 at 08:43:40PM +0300, Alexey Dobriyan wrote: > > + len = sprintf(buf, "%d\n", READ_ONCE(*field)); > > READ_ONCE isn't necessary as there is only one read being made. Others might disagree but you shouldn't ever let gcc touch any memory that can change under gcc without

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, Jan 08, 2018 at 08:43:40PM +0300, Alexey Dobriyan wrote: > > + len = sprintf(buf, "%d\n", READ_ONCE(*field)); > > READ_ONCE isn't necessary as there is only one read being made. Others might disagree but you shouldn't ever let gcc touch any memory that can change under gcc without

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> + len = sprintf(buf, "%d\n", READ_ONCE(*field)); READ_ONCE isn't necessary as there is only one read being made. > + len = min(count, sizeof(buf) - 1); > + if (copy_from_user(buf, user_buf, len)) > + return -EFAULT; > + > + buf[len] = '\0'; > + if

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> + len = sprintf(buf, "%d\n", READ_ONCE(*field)); READ_ONCE isn't necessary as there is only one read being made. > + len = min(count, sizeof(buf) - 1); > + if (copy_from_user(buf, user_buf, len)) > + return -EFAULT; > + > + buf[len] = '\0'; > + if

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: > On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > >>> a good suggestion, but we encountered some issues with it either > >>> crashing the kernel at boot or not properly

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, Jan 08, 2018 at 09:28:12AM -0800, Tim Chen wrote: > On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > >>> a good suggestion, but we encountered some issues with it either > >>> crashing the kernel at boot or not properly

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: >>> a good suggestion, but we encountered some issues with it either >>> crashing the kernel at boot or not properly turning on/off. > > The below boots, but I lack stuff to test the

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/08/2018 08:14 AM, Peter Zijlstra wrote: > On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: >>> a good suggestion, but we encountered some issues with it either >>> crashing the kernel at boot or not properly turning on/off. > > The below boots, but I lack stuff to test the

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/08/2018 07:29 AM, Van De Ven, Arjan wrote: >>> + if ((!c->cpu_index) && (boot_cpu_has(X86_FEATURE_SPEC_CTRL))) { >> >> We should test X86_BUG_SPECTRE_V1 here too before default enabling this, >> no? > > > we shouldn't default enable this. > Patch 7 disables ibrs if retpoline is in use.

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/08/2018 07:29 AM, Van De Ven, Arjan wrote: >>> + if ((!c->cpu_index) && (boot_cpu_has(X86_FEATURE_SPEC_CTRL))) { >> >> We should test X86_BUG_SPECTRE_V1 here too before default enabling this, >> no? > > > we shouldn't default enable this. > Patch 7 disables ibrs if retpoline is in use.

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > a good suggestion, but we encountered some issues with it either > > crashing the kernel at boot or not properly turning on/off. The below boots, but I lack stuff to test the enabling. --- a/arch/x86/include/asm/spec_ctrl.h +++

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Mon, Jan 08, 2018 at 01:47:07PM +0100, Peter Zijlstra wrote: > > a good suggestion, but we encountered some issues with it either > > crashing the kernel at boot or not properly turning on/off. The below boots, but I lack stuff to test the enabling. --- a/arch/x86/include/asm/spec_ctrl.h +++

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > +static ssize_t ibrs_enabled_write(struct file *file, > + const char __user *user_buf, > + size_t count, loff_t *ppos) > +{ > + char buf[32]; > + ssize_t len; > +

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > +static ssize_t ibrs_enabled_write(struct file *file, > + const char __user *user_buf, > + size_t count, loff_t *ppos) > +{ > + char buf[32]; > + ssize_t len; > +

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> > + if ((!c->cpu_index) && (boot_cpu_has(X86_FEATURE_SPEC_CTRL))) { > > We should test X86_BUG_SPECTRE_V1 here too before default enabling this, > no? we shouldn't default enable this.

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> > + if ((!c->cpu_index) && (boot_cpu_has(X86_FEATURE_SPEC_CTRL))) { > > We should test X86_BUG_SPECTRE_V1 here too before default enabling this, > no? we shouldn't default enable this.

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > +static void spec_ctrl_flush_all_cpus(u32 msr_nr, u64 val) > +{ > + int cpu; > + > + get_online_cpus(); > + for_each_online_cpu(cpu) > + wrmsrl_on_cpu(cpu, msr_nr, val); > + put_online_cpus(); > +} > + >

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > +static void spec_ctrl_flush_all_cpus(u32 msr_nr, u64 val) > +{ > + int cpu; > + > + get_online_cpus(); > + for_each_online_cpu(cpu) > + wrmsrl_on_cpu(cpu, msr_nr, val); > + put_online_cpus(); > +} > + >

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > +bool ibrs_inuse(void); > +bool ibrs_inuse(void) > +{ > + return ibrs_enabled == IBRS_ENABLED; > +} > +EXPORT_SYMBOL_GPL(ibrs_inuse); Doesn't appear to actually be used anywhere...

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > +bool ibrs_inuse(void); > +bool ibrs_inuse(void) > +{ > + return ibrs_enabled == IBRS_ENABLED; > +} > +EXPORT_SYMBOL_GPL(ibrs_inuse); Doesn't appear to actually be used anywhere...

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > +void scan_spec_ctrl_feature(struct cpuinfo_x86 *c) > +{ > + if ((!c->cpu_index) && (boot_cpu_has(X86_FEATURE_SPEC_CTRL))) { We should test X86_BUG_SPECTRE_V1 here too before default enabling this, no? > + if

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > +void scan_spec_ctrl_feature(struct cpuinfo_x86 *c) > +{ > + if ((!c->cpu_index) && (boot_cpu_has(X86_FEATURE_SPEC_CTRL))) { We should test X86_BUG_SPECTRE_V1 here too before default enabling this, no? > + if

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 07:12:12PM -0800, Dave Hansen wrote: > On 01/05/2018 06:12 PM, Tim Chen wrote: > > .macro ENABLE_IBRS > > - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > > + testl $1, dynamic_ibrs > > + jz .Lskip_\@ > > There was an earlier suggestion to use

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 07:12:12PM -0800, Dave Hansen wrote: > On 01/05/2018 06:12 PM, Tim Chen wrote: > > .macro ENABLE_IBRS > > - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > > + testl $1, dynamic_ibrs > > + jz .Lskip_\@ > > There was an earlier suggestion to use

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 04:25:19PM -0500, Konrad Rzeszutek Wilk wrote: > On Sat, Jan 06, 2018 at 10:10:59AM -0800, Tim Chen wrote: > > > > > > On 01/06/2018 12:54 AM, Greg KH wrote: > > > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > > >> From: Tim Chen

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 04:25:19PM -0500, Konrad Rzeszutek Wilk wrote: > On Sat, Jan 06, 2018 at 10:10:59AM -0800, Tim Chen wrote: > > > > > > On 01/06/2018 12:54 AM, Greg KH wrote: > > > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > > >> From: Tim Chen > > >> From: Andrea

Is: Linus, name for 'spectre' variable. Was:Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 10:39:27PM +0100, Thomas Gleixner wrote: > On Sat, 6 Jan 2018, Konrad Rzeszutek Wilk wrote: > > On Sat, Jan 06, 2018 at 08:47:19PM +0100, Thomas Gleixner wrote: > > > On Sat, 6 Jan 2018, Dave Hansen wrote: > > > > > > > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > >

Is: Linus, name for 'spectre' variable. Was:Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 10:39:27PM +0100, Thomas Gleixner wrote: > On Sat, 6 Jan 2018, Konrad Rzeszutek Wilk wrote: > > On Sat, Jan 06, 2018 at 08:47:19PM +0100, Thomas Gleixner wrote: > > > On Sat, 6 Jan 2018, Dave Hansen wrote: > > > > > > > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > >

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> > it's a mistake though... retpoline is what people should be using > > ... and only in super exception cases should IBRS even be considered > > Like on certain Skylake and Broadwell where using the retpoline won't suffice? skylake is a bit more complex but that was discussed in earlier

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> > it's a mistake though... retpoline is what people should be using > > ... and only in super exception cases should IBRS even be considered > > Like on certain Skylake and Broadwell where using the retpoline won't suffice? skylake is a bit more complex but that was discussed in earlier

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 09:34:01PM +, Van De Ven, Arjan wrote: > > I agree. But this is what customers are told to inspect to see if they > > are impacted. And if in the future versions this goes away or such - they > > will freak out and cause needless escalations. > > > it's a mistake

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 09:34:01PM +, Van De Ven, Arjan wrote: > > I agree. But this is what customers are told to inspect to see if they > > are impacted. And if in the future versions this goes away or such - they > > will freak out and cause needless escalations. > > > it's a mistake

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, 6 Jan 2018, Konrad Rzeszutek Wilk wrote: > On Sat, Jan 06, 2018 at 08:47:19PM +0100, Thomas Gleixner wrote: > > On Sat, 6 Jan 2018, Dave Hansen wrote: > > > > > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > > > .macro DISABLE_IBRS > > > -ALTERNATIVE "jmp .Lskip_\@",

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, 6 Jan 2018, Konrad Rzeszutek Wilk wrote: > On Sat, Jan 06, 2018 at 08:47:19PM +0100, Thomas Gleixner wrote: > > On Sat, 6 Jan 2018, Dave Hansen wrote: > > > > > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > > > .macro DISABLE_IBRS > > > -ALTERNATIVE "jmp .Lskip_\@",

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> I agree. But this is what customers are told to inspect to see if they > are impacted. And if in the future versions this goes away or such - they > will freak out and cause needless escalations. it's a mistake though... retpoline is what people should be using ... and only in super

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> I agree. But this is what customers are told to inspect to see if they > are impacted. And if in the future versions this goes away or such - they > will freak out and cause needless escalations. it's a mistake though... retpoline is what people should be using ... and only in super

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 08:47:19PM +0100, Thomas Gleixner wrote: > On Sat, 6 Jan 2018, Dave Hansen wrote: > > > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > > .macro DISABLE_IBRS > > - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > > + testl $1,

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 08:47:19PM +0100, Thomas Gleixner wrote: > On Sat, 6 Jan 2018, Dave Hansen wrote: > > > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > > .macro DISABLE_IBRS > > - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > > + testl $1,

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 10:10:59AM -0800, Tim Chen wrote: > > > On 01/06/2018 12:54 AM, Greg KH wrote: > > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > >> From: Tim Chen > >> From: Andrea Arcangeli > >> > >> There are 2 ways to

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, Jan 06, 2018 at 10:10:59AM -0800, Tim Chen wrote: > > > On 01/06/2018 12:54 AM, Greg KH wrote: > > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > >> From: Tim Chen > >> From: Andrea Arcangeli > >> > >> There are 2 ways to control IBRS > >> > >> 1. At boot time > >>

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, 6 Jan 2018, Dave Hansen wrote: > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > .macro DISABLE_IBRS > -ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > +testl $1, dynamic_ibrs > >>> On every system call we end up hammering on this

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Sat, 6 Jan 2018, Dave Hansen wrote: > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > .macro DISABLE_IBRS > -ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > +testl $1, dynamic_ibrs > >>> On every system call we end up hammering on this

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: .macro DISABLE_IBRS - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL + testl $1, dynamic_ibrs >>> On every system call we end up hammering on this 'dynamic_ibrs' >>> variable. And it looks like it can be flipped via the

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: .macro DISABLE_IBRS - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL + testl $1, dynamic_ibrs >>> On every system call we end up hammering on this 'dynamic_ibrs' >>> variable. And it looks like it can be flipped via the

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 09:33 AM, Dave Hansen wrote: > On 01/06/2018 06:41 AM, Konrad Rzeszutek Wilk wrote: >>> .macro DISABLE_IBRS >>> - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL >>> + testl $1, dynamic_ibrs >> On every system call we end up hammering on this 'dynamic_ibrs' >>

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 09:33 AM, Dave Hansen wrote: > On 01/06/2018 06:41 AM, Konrad Rzeszutek Wilk wrote: >>> .macro DISABLE_IBRS >>> - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL >>> + testl $1, dynamic_ibrs >> On every system call we end up hammering on this 'dynamic_ibrs' >>

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 06:41 AM, Konrad Rzeszutek Wilk wrote: > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: >> From: Tim Chen >> From: Andrea Arcangeli >> > >> >> .macro DISABLE_IBRS >> -ALTERNATIVE "jmp .Lskip_\@", "",

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 06:41 AM, Konrad Rzeszutek Wilk wrote: > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: >> From: Tim Chen >> From: Andrea Arcangeli >> > >> >> .macro DISABLE_IBRS >> -ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL >> +testl $1, dynamic_ibrs > > On

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 12:54 AM, Greg KH wrote: > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: >> From: Tim Chen >> From: Andrea Arcangeli >> >> There are 2 ways to control IBRS >> >> 1. At boot time >> noibrs kernel boot parameter will

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 12:54 AM, Greg KH wrote: > On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: >> From: Tim Chen >> From: Andrea Arcangeli >> >> There are 2 ways to control IBRS >> >> 1. At boot time >> noibrs kernel boot parameter will disable IBRS usage >> >> Otherwise if the above

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> >> .macro DISABLE_IBRS > >> - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > >> + testl $1, dynamic_ibrs > > On every system call we end up hammering on this 'dynamic_ibrs' > > variable. And it looks like it can be flipped via the IPI mechanism. > > > > Would it make sense for

RE: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

> >> .macro DISABLE_IBRS > >> - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > >> + testl $1, dynamic_ibrs > > On every system call we end up hammering on this 'dynamic_ibrs' > > variable. And it looks like it can be flipped via the IPI mechanism. > > > > Would it make sense for

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 06:41 AM, Konrad Rzeszutek Wilk wrote: >> .macro DISABLE_IBRS >> -ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL >> +testl $1, dynamic_ibrs > On every system call we end up hammering on this 'dynamic_ibrs' > variable. And it looks like it can be flipped via the IPI

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/06/2018 06:41 AM, Konrad Rzeszutek Wilk wrote: >> .macro DISABLE_IBRS >> -ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL >> +testl $1, dynamic_ibrs > On every system call we end up hammering on this 'dynamic_ibrs' > variable. And it looks like it can be flipped via the IPI

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > From: Tim Chen > From: Andrea Arcangeli > > There are 2 ways to control IBRS > > 1. At boot time > noibrs kernel boot parameter will disable IBRS usage > > Otherwise if the above

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > From: Tim Chen > From: Andrea Arcangeli > > There are 2 ways to control IBRS > > 1. At boot time > noibrs kernel boot parameter will disable IBRS usage > > Otherwise if the above parameters are not specified, the system > will

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > From: Tim Chen > From: Andrea Arcangeli > > There are 2 ways to control IBRS > > 1. At boot time > noibrs kernel boot parameter will disable IBRS usage > > Otherwise if the above

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On Fri, Jan 05, 2018 at 06:12:19PM -0800, Tim Chen wrote: > From: Tim Chen > From: Andrea Arcangeli > > There are 2 ways to control IBRS > > 1. At boot time > noibrs kernel boot parameter will disable IBRS usage > > Otherwise if the above parameters are not specified, the system > will

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/05/2018 06:12 PM, Tim Chen wrote: > .macro ENABLE_IBRS > - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > + testl $1, dynamic_ibrs > + jz .Lskip_\@ There was an earlier suggestion to use STATIC_JUMP_IF_... here. That's a good suggestion, but we encountered

Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

On 01/05/2018 06:12 PM, Tim Chen wrote: > .macro ENABLE_IBRS > - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > + testl $1, dynamic_ibrs > + jz .Lskip_\@ There was an earlier suggestion to use STATIC_JUMP_IF_... here. That's a good suggestion, but we encountered

[PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

From: Tim Chen From: Andrea Arcangeli There are 2 ways to control IBRS 1. At boot time noibrs kernel boot parameter will disable IBRS usage Otherwise if the above parameters are not specified, the system will enable ibrs and ibpb usage if

[PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature

From: Tim Chen From: Andrea Arcangeli There are 2 ways to control IBRS 1. At boot time noibrs kernel boot parameter will disable IBRS usage Otherwise if the above parameters are not specified, the system will enable ibrs and ibpb usage if the cpu supports it. 2. At run time echo 0 >