* [PATCH] ARM: virt: Relax arch timer version check during early boot
@ 2020-01-15 14:16 ` Vladimir Murzin
0 siblings, 0 replies; 10+ messages in thread
From: Vladimir Murzin @ 2020-01-15 14:16 UTC (permalink / raw)
To: linux-arm-kernel; +Cc: kbuild-all
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>
---
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
--
2.7.4
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^ permalink raw reply related [flat|nested] 10+ messages in thread
* [PATCH] ARM: virt: Relax arch timer version check during early boot
@ 2020-01-15 14:16 ` Vladimir Murzin
0 siblings, 0 replies; 10+ messages in thread
From: Vladimir Murzin @ 2020-01-15 14:16 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 1298 bytes --]
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>
---
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
--
2.7.4
^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
2020-01-15 14:16 ` Vladimir Murzin
@ 2020-01-20 10:46 ` Vladimir Murzin
-1 siblings, 0 replies; 10+ messages in thread
From: Vladimir Murzin @ 2020-01-20 10:46 UTC (permalink / raw)
To: linux-arm-kernel; +Cc: maz, kvmarm
+ 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>
> ---
> 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
>
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
@ 2020-01-20 10:46 ` Vladimir Murzin
0 siblings, 0 replies; 10+ messages in thread
From: Vladimir Murzin @ 2020-01-20 10:46 UTC (permalink / raw)
To: linux-arm-kernel; +Cc: maz, kvmarm
+ 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>
> ---
> 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
>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
2020-01-20 10:46 ` Vladimir Murzin
@ 2020-01-20 11:14 ` Marc Zyngier
-1 siblings, 0 replies; 10+ messages in thread
From: Marc Zyngier @ 2020-01-20 11:14 UTC (permalink / raw)
To: Vladimir Murzin; +Cc: kvmarm, linux-arm-kernel
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...
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
@ 2020-01-20 11:14 ` Marc Zyngier
0 siblings, 0 replies; 10+ messages in thread
From: Marc Zyngier @ 2020-01-20 11:14 UTC (permalink / raw)
To: Vladimir Murzin; +Cc: kvmarm, linux-arm-kernel
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...
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
2020-01-20 11:14 ` Marc Zyngier
@ 2020-01-20 11:34 ` Vladimir Murzin
-1 siblings, 0 replies; 10+ messages in thread
From: Vladimir Murzin @ 2020-01-20 11:34 UTC (permalink / raw)
To: Marc Zyngier; +Cc: kvmarm, linux-arm-kernel
Hi Marc,
On 1/20/20 11:14 AM, Marc Zyngier wrote:
> 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.
That true, ARM ARM doesn't mention it yet. OTOH, should we really care about exact
values as soon it stays compatible?
Cheers
Vladimir
>
> 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
>>>
>
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
@ 2020-01-20 11:34 ` Vladimir Murzin
0 siblings, 0 replies; 10+ messages in thread
From: Vladimir Murzin @ 2020-01-20 11:34 UTC (permalink / raw)
To: Marc Zyngier; +Cc: kvmarm, linux-arm-kernel
Hi Marc,
On 1/20/20 11:14 AM, Marc Zyngier wrote:
> 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.
That true, ARM ARM doesn't mention it yet. OTOH, should we really care about exact
values as soon it stays compatible?
Cheers
Vladimir
>
> 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
>>>
>
_______________________________________________
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
2020-01-20 11:34 ` Vladimir Murzin
@ 2020-01-20 11:56 ` Marc Zyngier
-1 siblings, 0 replies; 10+ messages in thread
From: Marc Zyngier @ 2020-01-20 11:56 UTC (permalink / raw)
To: Vladimir Murzin; +Cc: kvmarm, linux-arm-kernel
On 2020-01-20 12:34, Vladimir Murzin wrote:
> Hi Marc,
>
> On 1/20/20 11:14 AM, Marc Zyngier wrote:
>> 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.
>
> That true, ARM ARM doesn't mention it yet. OTOH, should we really care
> about exact values as soon it stays compatible?
That's for you to say, really. But given that you hint at some changes,
it'd be good to have at least a short sentence explaining that, for
example,
"upcoming revisions of the architecture will allow different
ID_PFR1.GenTimer
values while preserving backward compatibility".
Other than that, feel free to add my
Acked-by: Marc Zyngier <maz@kernel.org>
Thanks,
M.
--
Jazz is not dead. It just smells funny...
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] ARM: virt: Relax arch timer version check during early boot
@ 2020-01-20 11:56 ` Marc Zyngier
0 siblings, 0 replies; 10+ messages in thread
From: Marc Zyngier @ 2020-01-20 11:56 UTC (permalink / raw)
To: Vladimir Murzin; +Cc: kvmarm, linux-arm-kernel
On 2020-01-20 12:34, Vladimir Murzin wrote:
> Hi Marc,
>
> On 1/20/20 11:14 AM, Marc Zyngier wrote:
>> 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.
>
> That true, ARM ARM doesn't mention it yet. OTOH, should we really care
> about exact values as soon it stays compatible?
That's for you to say, really. But given that you hint at some changes,
it'd be good to have at least a short sentence explaining that, for
example,
"upcoming revisions of the architecture will allow different
ID_PFR1.GenTimer
values while preserving backward compatibility".
Other than that, feel free to add my
Acked-by: Marc Zyngier <maz@kernel.org>
Thanks,
M.
--
Jazz is not dead. It just smells funny...
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 10+ messages in thread
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2020-01-15 14:16 [PATCH] ARM: virt: Relax arch timer version check during early boot Vladimir Murzin
2020-01-15 14:16 ` Vladimir Murzin
2020-01-20 10:46 ` Vladimir Murzin
2020-01-20 10:46 ` Vladimir Murzin
2020-01-20 11:14 ` Marc Zyngier
2020-01-20 11:14 ` Marc Zyngier
2020-01-20 11:34 ` Vladimir Murzin
2020-01-20 11:34 ` Vladimir Murzin
2020-01-20 11:56 ` Marc Zyngier
2020-01-20 11:56 ` Marc Zyngier
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