| Message ID | 20230628022554.1638318-2-longman@redhat.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | x86/speculation: Disable IBRS when idle | expand |
On Tue, Jun 27, 2023 at 10:25:51PM -0400, Waiman Long wrote: > Add a new __update_spec_ctrl() helper which is a variant of > update_spec_ctrl() that can be used in a noinstr function. > > Suggested-by: Peter Zijlstra <peterz@infradead.org> > Signed-off-by: Waiman Long <longman@redhat.com> > --- > arch/x86/include/asm/nospec-branch.h | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h > index 55388c9f7601..1d363fcea207 100644 > --- a/arch/x86/include/asm/nospec-branch.h > +++ b/arch/x86/include/asm/nospec-branch.h > @@ -9,7 +9,7 @@ > > #include <asm/alternative.h> > #include <asm/cpufeatures.h> > -#include <asm/msr-index.h> > +#include <asm/msr.h> > #include <asm/unwind_hints.h> > #include <asm/percpu.h> > #include <asm/current.h> > @@ -488,6 +488,15 @@ DECLARE_PER_CPU(u64, x86_spec_ctrl_current); > extern void update_spec_ctrl_cond(u64 val); > extern u64 spec_ctrl_current(void); > > +/* > + * This can be used in noinstr function. > + */ > +static __always_inline void __update_spec_ctrl(u64 val) > +{ > + __this_cpu_write(x86_spec_ctrl_current, val); > + native_wrmsrl(MSR_IA32_SPEC_CTRL, val); > +} Should we also use this to implement update_spec_ctrl() ?
On 7/3/23 06:28, Peter Zijlstra wrote: > On Tue, Jun 27, 2023 at 10:25:51PM -0400, Waiman Long wrote: >> Add a new __update_spec_ctrl() helper which is a variant of >> update_spec_ctrl() that can be used in a noinstr function. >> >> Suggested-by: Peter Zijlstra <peterz@infradead.org> >> Signed-off-by: Waiman Long <longman@redhat.com> >> --- >> arch/x86/include/asm/nospec-branch.h | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h >> index 55388c9f7601..1d363fcea207 100644 >> --- a/arch/x86/include/asm/nospec-branch.h >> +++ b/arch/x86/include/asm/nospec-branch.h >> @@ -9,7 +9,7 @@ >> >> #include <asm/alternative.h> >> #include <asm/cpufeatures.h> >> -#include <asm/msr-index.h> >> +#include <asm/msr.h> >> #include <asm/unwind_hints.h> >> #include <asm/percpu.h> >> #include <asm/current.h> >> @@ -488,6 +488,15 @@ DECLARE_PER_CPU(u64, x86_spec_ctrl_current); >> extern void update_spec_ctrl_cond(u64 val); >> extern u64 spec_ctrl_current(void); >> >> +/* >> + * This can be used in noinstr function. >> + */ >> +static __always_inline void __update_spec_ctrl(u64 val) >> +{ >> + __this_cpu_write(x86_spec_ctrl_current, val); >> + native_wrmsrl(MSR_IA32_SPEC_CTRL, val); >> +} > Should we also use this to implement update_spec_ctrl() ? I also thought about that. However, I am a bit worry about losing some additional check done in this_cpu_write() and the paravirt support in wrmsrl(). I have no problem making update_spec_ctrl() an instrument-able wrapper on __update_spec_ctrl() if you think these are not valid concerns. Cheers, Longman
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 55388c9f7601..1d363fcea207 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -9,7 +9,7 @@ #include <asm/alternative.h> #include <asm/cpufeatures.h> -#include <asm/msr-index.h> +#include <asm/msr.h> #include <asm/unwind_hints.h> #include <asm/percpu.h> #include <asm/current.h> @@ -488,6 +488,15 @@ DECLARE_PER_CPU(u64, x86_spec_ctrl_current); extern void update_spec_ctrl_cond(u64 val); extern u64 spec_ctrl_current(void); +/* + * This can be used in noinstr function. + */ +static __always_inline void __update_spec_ctrl(u64 val) +{ + __this_cpu_write(x86_spec_ctrl_current, val); + native_wrmsrl(MSR_IA32_SPEC_CTRL, val); +} + /* * With retpoline, we must use IBRS to restrict branch prediction * before calling into firmware.
Add a new __update_spec_ctrl() helper which is a variant of update_spec_ctrl() that can be used in a noinstr function. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Waiman Long <longman@redhat.com> --- arch/x86/include/asm/nospec-branch.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)