From: Marc Zyngier <maz@kernel.org>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
Date: Mon, 20 Jan 2020 12:14:04 +0100 [thread overview]
Message-ID: <d4b8bb91f95385682f20c9dc5c6f5e50@kernel.org> (raw)
In-Reply-To: <eb889279-87f2-d674-9299-169794c285eb@arm.com>
Hi Vladimir,
On 2020-01-20 11:46, Vladimir Murzin wrote:
> + Marc
> + kvmarm@lists.cs.columbia.edu
>
> On 1/15/20 2:16 PM, Vladimir Murzin wrote:
>> Updates to the Generic Timer architecture allow ID_PFR1.GenTimer to
>> have values other than 0 or 1. At the moment, Linux is quite strict in
>> the way it handles this field at early boot and will not configure
>> arch timer if it doesn't find the value 1.
>>
>> Since here use ubfx for arch timer version extraction (hyb-stub build
>> with -march=armv7-a, so it is safe)
>>
>> To help backports (even though the code was correct at the time of
>> writing)
>> Fixes: 8ec58be9f3ff ("ARM: virt: arch_timers: enable access to
>> physical timers")
>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
I'm not opposed to such a change, but it'd be good to document what
other values
are expected here, as the current (Rev E_a) ARM ARM only mentions values
0 and 1.
Thanks,
M.
>> ---
>> arch/arm/kernel/hyp-stub.S | 7 +++----
>> 1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S
>> index ae50203..6607fa8 100644
>> --- a/arch/arm/kernel/hyp-stub.S
>> +++ b/arch/arm/kernel/hyp-stub.S
>> @@ -146,10 +146,9 @@ ARM_BE8(orr r7, r7, #(1 << 25)) @ HSCTLR.EE
>> #if !defined(ZIMAGE) && defined(CONFIG_ARM_ARCH_TIMER)
>> @ make CNTP_* and CNTPCT accessible from PL1
>> mrc p15, 0, r7, c0, c1, 1 @ ID_PFR1
>> - lsr r7, #16
>> - and r7, #0xf
>> - cmp r7, #1
>> - bne 1f
>> + ubfx r7, r7, #16, #4
>> + teq r7, #0
>> + beq 1f
>> mrc p15, 4, r7, c14, c1, 0 @ CNTHCTL
>> orr r7, r7, #3 @ PL1PCEN | PL1PCTEN
>> mcr p15, 4, r7, c14, c1, 0 @ CNTHCTL
>>
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2020-01-20 11:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 14:16 [PATCH] ARM: virt: Relax arch timer version check during early boot Vladimir Murzin
2020-01-20 10:46 ` Vladimir Murzin
2020-01-20 11:14 ` Marc Zyngier [this message]
2020-01-20 11:34 ` Vladimir Murzin
2020-01-20 11:56 ` Marc Zyngier
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