Re: [PATCH 06/12] x86/mm: use INVLPGB for kernel TLB flushes

[Rik van Riel]

On Fri, 2025-01-10 at 12:53 -0600, Tom Lendacky wrote:
> On 12/30/24 11:53, Rik van Riel wrote:
> > Use broadcast TLB invalidation for kernel addresses when available.
> > 
> > +static void broadcast_kernel_range_flush(unsigned long start,
> > unsigned long end)
> > +{
> > +	unsigned long addr;
> > +	unsigned long maxnr = invlpgb_count_max;
> > +	unsigned long threshold = tlb_single_page_flush_ceiling *
> > maxnr;
> > +
> > +	/*
> > +	 * TLBSYNC only waits for flushes originating on the same
> > CPU.
> > +	 * Disabling migration allows us to wait on all flushes.
> > +	 */
> > +	guard(preempt)();
> > +
> > +	if (end == TLB_FLUSH_ALL ||
> > +	    (end - start) > threshold << PAGE_SHIFT) {
> > +		invlpgb_flush_all();
> > +	} else {
> > +		unsigned long nr;
> > +		for (addr = start; addr < end; addr += nr <<
> > PAGE_SHIFT) {
> > +			nr = min((end - addr) >> PAGE_SHIFT,
> > maxnr);
> > +			invlpgb_flush_addr(addr, nr);
> > +		}
> 
> Would it be better to put this loop in the actual invlpgb_flush*
> function(s)? Then callers don't have to worry about it, similar to
> what is
> done in clflush_cache_range() / clflush_cache_range_opt().

Maybe?

We only have one caller, though.


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