Re: [PATCH v13 05/14] x86/mm: use INVLPGB in flush_tlb_all

Borislav Petkov
2025-02-24T12:46:43Z

On Sun, Feb 23, 2025 at 02:48:55PM -0500, Rik van Riel wrote:
> The flush_tlb_all() function is not used a whole lot, but we might
> as well use broadcast TLB flushing there, too.
>
> Signed-off-by: Rik van Riel <riel@surriel.com>
> Tested-by: Manali Shukla <Manali.Shukla@amd.com>
> Tested-by: Brendan Jackman <jackmanb@google.com>
> Tested-by: Michael Kelley <mhklinux@outlook.com>
> ---
> arch/x86/mm/tlb.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index 59396a3c6e9c..2d7ed0fda61f 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -1065,6 +1065,16 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
> }
>
>
> +static bool broadcast_flush_tlb_all(void)

broadcast?

All those INVLPGB functions have a "invlpgb_" prefix...

In any case, get rid of that function:

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 2d7ed0fda61f..feaca53b7685 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -1065,16 +1065,6 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
}

-static bool broadcast_flush_tlb_all(void)
-{
- if (!cpu_feature_enabled(X86_FEATURE_INVLPGB))
- return false;
-
- guard(preempt)();
- invlpgb_flush_all();
- return true;
-}
-
static void do_flush_tlb_all(void *info)
{
count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
@@ -1085,9 +1075,11 @@ void flush_tlb_all(void)
{
count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);

- /* First try (faster) hardware-assisted TLB invalidation. */
- if (broadcast_flush_tlb_all())
+ if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) {
+ guard(preempt)();
+ invlpgb_flush_all();
return;
+ }

/* Fall back to the IPI-based invalidation. */
on_each_cpu(do_flush_tlb_all, NULL, 1);

--
Regards/Gruss,
Boris.