linux-kernel - Re: [RFC 04/10] x86/mm: Pass flush_tlb_info to flush_tlb

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Date:   Thu, 11 May 2017 13:01:44 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Nadav Amit <namit@...are.com>, Michal Hocko <mhocko@...e.com>,
        Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [RFC 04/10] x86/mm: Pass flush_tlb_info to flush_tlb_others() etc


> On May 7, 2017, at 5:38 AM, Andy Lutomirski <luto@...nel.org> wrote:
> 
> @@ -243,15 +237,15 @@ static void flush_tlb_func(void *info)
> 		return;
> 	}
> 
> -	if (f->flush_end == TLB_FLUSH_ALL) {
> +	if (f->end == TLB_FLUSH_ALL) {
> 		local_flush_tlb();
> 		trace_tlb_flush(TLB_REMOTE_SHOOTDOWN, TLB_FLUSH_ALL);
> 	} else {
> 		unsigned long addr;
> 		unsigned long nr_pages =
> -			(f->flush_end - f->flush_start) / PAGE_SIZE;
> -		addr = f->flush_start;
> -		while (addr < f->flush_end) {
> +			(f->end - f->start) / PAGE_SIZE;
> +		addr = f->start;
> +		while (addr < f->end) {
> 			__flush_tlb_single(addr);
> 			addr += PAGE_SIZE;
> 		}
> @@ -260,33 +254,27 @@ static void flush_tlb_func(void *info)
> }
> 
> void native_flush_tlb_others(const struct cpumask *cpumask,
> -				 struct mm_struct *mm, unsigned long start,
> -				 unsigned long end)
> +			     const struct flush_tlb_info *info)
> {
> -	struct flush_tlb_info info;
> -
> -	info.flush_mm = mm;
> -	info.flush_start = start;
> -	info.flush_end = end;
> -
> 	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
> -	if (end == TLB_FLUSH_ALL)
> +	if (info->end == TLB_FLUSH_ALL)
> 		trace_tlb_flush(TLB_REMOTE_SEND_IPI, TLB_FLUSH_ALL);
> 	else
> 		trace_tlb_flush(TLB_REMOTE_SEND_IPI,
> -				(end - start) >> PAGE_SHIFT);
> +				(info->end - info->start) >> PAGE_SHIFT);

I know it is stupid, but since you already change the code, can you make
flush_tlb_func() and native_flush_tlb_others() consistent in the way
they compute the number of pages? (either ‘>> PAGE_SHIFT’ or ‘/ PAGE_SIZE’)?

On a different topic: I do not like or actually understand why TLBSTATE_OK
is defined as 1 and not 0. The very least it would generate a better code.

Thanks,
Nadav