In case of the generic cache interface being used (Intel CPUs or a
64-bit system), the initialization sequence of the boot CPU is more
complicated as necessary:
- check if MTRR enabled, if yes, call mtrr_bp_pat_init() which will
disable caching, set the PAT MSR, and reenable caching
- call mtrr_cleanup(), in case that changed anything, call
cache_cpu_init() doing the same caching disable/enable dance as
above, but this time with setting the (modified) MTRR state (even
if MTRR was disabled) AND setting the PAT MSR (again even with
disabled MTRR)
The sequence can be simplified a lot while removing potential
inconsistencies:
- check if MTRR enabled, if yes, call mtrr_cleanup() and then
cache_cpu_init()
This ensures to:
- no longer disable/enable caching more than once
- avoid to set MTRRs and/or the PAT MSR on the boot processor in case
of MTRR cleanups even if MTRRs meant to be disabled
With that mtrr_bp_pat_init() can be removed.
Signed-off-by: Juergen Gross <[email protected]>
---
V2:
- new patch
---
arch/x86/kernel/cpu/mtrr/generic.c | 14 --------------
arch/x86/kernel/cpu/mtrr/mtrr.c | 6 +-----
arch/x86/kernel/cpu/mtrr/mtrr.h | 1 -
3 files changed, 1 insertion(+), 20 deletions(-)
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index af8422c96b92..2f2485d6657f 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -442,20 +442,6 @@ static void __init print_mtrr_state(void)
pr_debug("TOM2: %016llx aka %lldM\n", mtrr_tom2, mtrr_tom2>>20);
}
-/* PAT setup for BP. We need to go through sync steps here */
-void __init mtrr_bp_pat_init(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- cache_disable();
-
- pat_init();
-
- cache_enable();
- local_irq_restore(flags);
-}
-
/* Grab all of the MTRR state for this CPU into *state */
bool __init get_mtrr_state(void)
{
diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
index 501ca1747d55..9e1b478ac896 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.c
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
@@ -759,12 +759,8 @@ void __init mtrr_bp_init(void)
mtrr_enabled = get_mtrr_state();
if (mtrr_enabled) {
- mtrr_bp_pat_init();
memory_caching_control |= CACHE_MTRR | CACHE_PAT;
- }
-
- if (mtrr_cleanup(phys_addr)) {
- changed_by_mtrr_cleanup = 1;
+ changed_by_mtrr_cleanup = mtrr_cleanup(phys_addr);
cache_cpu_init();
}
}
diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.h b/arch/x86/kernel/cpu/mtrr/mtrr.h
index 3b1883185185..c98928ceee6a 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.h
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.h
@@ -50,7 +50,6 @@ void set_mtrr_prepare_save(struct set_mtrr_context *ctxt);
void fill_mtrr_var_range(unsigned int index,
u32 base_lo, u32 base_hi, u32 mask_lo, u32 mask_hi);
bool get_mtrr_state(void);
-void mtrr_bp_pat_init(void);
extern void __init set_mtrr_ops(const struct mtrr_ops *ops);
--
2.35.3
On Tue, Oct 04, 2022 at 10:10:16AM +0200, Juergen Gross wrote:
> In case of the generic cache interface being used (Intel CPUs or a
> 64-bit system), the initialization sequence of the boot CPU is more
> complicated as necessary:
s/as/than/
>
> - check if MTRR enabled, if yes, call mtrr_bp_pat_init() which will
> disable caching, set the PAT MSR, and reenable caching
>
> - call mtrr_cleanup(), in case that changed anything, call
> cache_cpu_init() doing the same caching disable/enable dance as
> above, but this time with setting the (modified) MTRR state (even
> if MTRR was disabled) AND setting the PAT MSR (again even with
> disabled MTRR)
>
> The sequence can be simplified a lot while removing potential
> inconsistencies:
>
> - check if MTRR enabled, if yes, call mtrr_cleanup() and then
> cache_cpu_init()
>
> This ensures to:
>
> - no longer disable/enable caching more than once
>
> - avoid to set MTRRs and/or the PAT MSR on the boot processor in case
> of MTRR cleanups even if MTRRs meant to be disabled
>
> With that mtrr_bp_pat_init() can be removed.
I like that simplification - I just hope there's not some weird ordering
that is still needed. But we'll see when this hits the wider audiences.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette