linux-kernel - Re: [PATCH 22/30] x86, pcid, kaiser: allow flushing for future ASID switches

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Message-ID: <20171110122502.s2i6od7lx4uooyyu@hirez.programming.kicks-ass.net>
Date:   Fri, 10 Nov 2017 13:25:02 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        moritz.lipp@...k.tugraz.at, daniel.gruss@...k.tugraz.at,
        michael.schwarz@...k.tugraz.at, richard.fellner@...dent.tugraz.at,
        luto@...nel.org, torvalds@...ux-foundation.org,
        keescook@...gle.com, hughd@...gle.com, x86@...nel.org
Subject: Re: [PATCH 22/30] x86, pcid, kaiser: allow flushing for future ASID
 switches

On Wed, Nov 08, 2017 at 11:47:28AM -0800, Dave Hansen wrote:
> +/*
> + * We get here when we do something requiring a TLB invalidation
> + * but could not go invalidate all of the contexts.  We do the
> + * necessary invalidation by clearing out the 'ctx_id' which
> + * forces a TLB flush when the context is loaded.
> + */
> +void clear_non_loaded_ctxs(void)
> +{
> +	u16 asid;
> +
> +	/*
> +	 * This is only expected to be set if we have disabled
> +	 * kernel _PAGE_GLOBAL pages.
> +	 */
> +        if (IS_ENABLED(CONFIG_X86_GLOBAL_PAGES)) {
> +		WARN_ON_ONCE(1);
> +                return;
> +	}

Whitespace damage..

> +
> +	for (asid = 0; asid < TLB_NR_DYN_ASIDS; asid++) {
> +		/* Do not need to flush the current asid */
> +		if (asid == this_cpu_read(cpu_tlbstate.loaded_mm_asid))
> +			continue;
> +		/*
> +		 * Make sure the next time we go to switch to
> +		 * this asid, we do a flush:
> +		 */
> +		this_cpu_write(cpu_tlbstate.ctxs[asid].ctx_id, 0);
> +	}
> +	this_cpu_write(cpu_tlbstate.all_other_ctxs_invalid, false);
> +}