From: Vladimir Murzin <vladimir.murzin@arm.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>,
catalin.marinas@arm.com, will@kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: context: Fix ASID limit in boot warning
Date: Mon, 24 Feb 2020 11:06:43 +0000 [thread overview]
Message-ID: <a54c1498-2fff-8d97-5220-e378966d3853@arm.com> (raw)
In-Reply-To: <20200224103934.137314-1-jean-philippe@linaro.org>
Hi Jean,
On 2/24/20 10:39 AM, Jean-Philippe Brucker wrote:
> Since commit f88f42f853a8 ("arm64: context: Free up kernel ASIDs if KPTI
> is not in use"), the NUM_USER_ASIDS macro doesn't correspond to the
> effective number of ASIDs when KPTI is enabled. Fix the number of
> available ASIDs in the boot warning.
>
> Fixes: f88f42f853a8 ("arm64: context: Free up kernel ASIDs if KPTI is not in use")
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
> arch/arm64/mm/context.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
> index 8ef73e89d514..121aba5b1941 100644
> --- a/arch/arm64/mm/context.c
> +++ b/arch/arm64/mm/context.c
> @@ -262,12 +262,16 @@ asmlinkage void post_ttbr_update_workaround(void)
>
> static int asids_init(void)
> {
> + unsigned long num_available_asids;
> + bool kpti = IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0);
> +
> asid_bits = get_cpu_asid_bits();
> /*
> * Expect allocation after rollover to fail if we don't have at least
> * one more ASID than CPUs. ASID #0 is reserved for init_mm.
> */
> - WARN_ON(NUM_USER_ASIDS - 1 <= num_possible_cpus());
> + num_available_asids = (1UL << (asid_bits - kpti)) - 1;
> + WARN_ON(num_available_asids <= num_possible_cpus());
> atomic64_set(&asid_generation, ASID_FIRST_VERSION);
> asid_map = kcalloc(BITS_TO_LONGS(NUM_USER_ASIDS), sizeof(*asid_map),
> GFP_KERNEL);
> @@ -280,7 +284,7 @@ static int asids_init(void)
> * caps are not finalized yet, so it is safer to assume KPTI
> * and reserve kernel ASID's from beginning.
> */
> - if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0))
> + if (kpti)
> set_kpti_asid_bits();
>
> pr_info("ASID allocator initialised with %lu entries\n", NUM_USER_ASIDS);
>
I agree with what you say about NUM_USER_ASIDS, yet looking at comment explaining
warning is seems that we may get extra ASIDs later on rollover, so warning might be
seen as false positive. Can we move the warning later on when we know how many ASIDs
we have after all CPU's are up? Maybe late_initcall?
Cheers
Vladimir
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next prev parent reply other threads:[~2020-02-24 11:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-24 10:39 [PATCH] arm64: context: Fix ASID limit in boot warning Jean-Philippe Brucker
2020-02-24 11:06 ` Vladimir Murzin [this message]
2020-02-25 12:13 ` Jean-Philippe Brucker
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