* [PATCH] iommu: Print default strict or lazy mode at init time
@ 2021-05-28 13:37 ` John Garry
0 siblings, 0 replies; 10+ messages in thread
From: John Garry @ 2021-05-28 13:37 UTC (permalink / raw)
To: joro, will; +Cc: iommu, linux-kernel, hch, robin.murphy, John Garry
As well as the default domain type, it's useful to know whether strict
or lazy mode is default for DMA domains, so add this info in a separate
print.
Signed-off-by: John Garry <john.garry@huawei.com>
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 808ab70d5df5..f25fae62f077 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
(iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
"(set via kernel command line)" : "");
+ pr_info("Default DMA domain mode: %s %s\n",
+ iommu_dma_strict ? "strict" : "lazy",
+ (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
+ "(set via kernel command line)" : "");
+
return 0;
}
subsys_initcall(iommu_subsys_init);
--
2.26.2
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH] iommu: Print default strict or lazy mode at init time
@ 2021-05-28 13:37 ` John Garry
0 siblings, 0 replies; 10+ messages in thread
From: John Garry @ 2021-05-28 13:37 UTC (permalink / raw)
To: joro, will; +Cc: iommu, robin.murphy, linux-kernel, hch
As well as the default domain type, it's useful to know whether strict
or lazy mode is default for DMA domains, so add this info in a separate
print.
Signed-off-by: John Garry <john.garry@huawei.com>
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 808ab70d5df5..f25fae62f077 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
(iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
"(set via kernel command line)" : "");
+ pr_info("Default DMA domain mode: %s %s\n",
+ iommu_dma_strict ? "strict" : "lazy",
+ (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
+ "(set via kernel command line)" : "");
+
return 0;
}
subsys_initcall(iommu_subsys_init);
--
2.26.2
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH] iommu: Print default strict or lazy mode at init time
2021-05-28 13:37 ` John Garry
@ 2021-06-01 9:09 ` Robin Murphy
-1 siblings, 0 replies; 10+ messages in thread
From: Robin Murphy @ 2021-06-01 9:09 UTC (permalink / raw)
To: John Garry, joro, will; +Cc: iommu, linux-kernel, hch
On 2021-05-28 14:37, John Garry wrote:
> As well as the default domain type, it's useful to know whether strict
> or lazy mode is default for DMA domains, so add this info in a separate
> print.
>
> Signed-off-by: John Garry <john.garry@huawei.com>
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 808ab70d5df5..f25fae62f077 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
> (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
> "(set via kernel command line)" : "");
>
> + pr_info("Default DMA domain mode: %s %s\n",
Nit: I think this might be a little unclear for end-users - *I'm* not
even sure whether "Default" here is meant to refer to the mode setting
itself or to default domains (of DMA type). Maybe something like "DMA
domain TLB invalidation policy"? Certainly it seems like a good idea to
explicitly mention invalidation to correlate with the documentation of
the "iommu.strict" parameter.
Ack to the general idea though.
Thanks,
Robin.
> + iommu_dma_strict ? "strict" : "lazy",
> + (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
> + "(set via kernel command line)" : "");
> +
> return 0;
> }
> subsys_initcall(iommu_subsys_init);
>
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] iommu: Print default strict or lazy mode at init time
@ 2021-06-01 9:09 ` Robin Murphy
0 siblings, 0 replies; 10+ messages in thread
From: Robin Murphy @ 2021-06-01 9:09 UTC (permalink / raw)
To: John Garry, joro, will; +Cc: iommu, linux-kernel, hch
On 2021-05-28 14:37, John Garry wrote:
> As well as the default domain type, it's useful to know whether strict
> or lazy mode is default for DMA domains, so add this info in a separate
> print.
>
> Signed-off-by: John Garry <john.garry@huawei.com>
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 808ab70d5df5..f25fae62f077 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
> (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
> "(set via kernel command line)" : "");
>
> + pr_info("Default DMA domain mode: %s %s\n",
Nit: I think this might be a little unclear for end-users - *I'm* not
even sure whether "Default" here is meant to refer to the mode setting
itself or to default domains (of DMA type). Maybe something like "DMA
domain TLB invalidation policy"? Certainly it seems like a good idea to
explicitly mention invalidation to correlate with the documentation of
the "iommu.strict" parameter.
Ack to the general idea though.
Thanks,
Robin.
> + iommu_dma_strict ? "strict" : "lazy",
> + (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
> + "(set via kernel command line)" : "");
> +
> return 0;
> }
> subsys_initcall(iommu_subsys_init);
>
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] iommu: Print default strict or lazy mode at init time
2021-06-01 9:09 ` Robin Murphy
@ 2021-06-01 15:50 ` John Garry
-1 siblings, 0 replies; 10+ messages in thread
From: John Garry @ 2021-06-01 15:50 UTC (permalink / raw)
To: Robin Murphy, joro, will; +Cc: iommu, linux-kernel, hch
On 01/06/2021 10:09, Robin Murphy wrote:
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 808ab70d5df5..f25fae62f077 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
>> (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
>> "(set via kernel command line)" : "");
>> + pr_info("Default DMA domain mode: %s %s\n",
>
> Nit: I think this might be a little unclear for end-users - *I'm* not
> even sure whether "Default" here is meant to refer to the mode setting
> itself or to default domains (of DMA type). Maybe something like "DMA
> domain TLB invalidation policy"? Certainly it seems like a good idea to
> explicitly mention invalidation to correlate with the documentation of
> the "iommu.strict" parameter.
>
> Ack to the general idea though.
ok, so I'll go with this:
pr_info("DMA domain default TLB invalidation policy: %s mode %s\n",
iommu_dma_strict ? "strict" : "lazy",
(iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
"(set via kernel command line)" : "");
I think it's worth mentioning "default" somewhere, as not all IOMMUs or
devices will use lazy mode even if it's default.
Thanks,
John
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] iommu: Print default strict or lazy mode at init time
@ 2021-06-01 15:50 ` John Garry
0 siblings, 0 replies; 10+ messages in thread
From: John Garry @ 2021-06-01 15:50 UTC (permalink / raw)
To: Robin Murphy, joro, will; +Cc: iommu, linux-kernel, hch
On 01/06/2021 10:09, Robin Murphy wrote:
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index 808ab70d5df5..f25fae62f077 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
>> (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
>> "(set via kernel command line)" : "");
>> + pr_info("Default DMA domain mode: %s %s\n",
>
> Nit: I think this might be a little unclear for end-users - *I'm* not
> even sure whether "Default" here is meant to refer to the mode setting
> itself or to default domains (of DMA type). Maybe something like "DMA
> domain TLB invalidation policy"? Certainly it seems like a good idea to
> explicitly mention invalidation to correlate with the documentation of
> the "iommu.strict" parameter.
>
> Ack to the general idea though.
ok, so I'll go with this:
pr_info("DMA domain default TLB invalidation policy: %s mode %s\n",
iommu_dma_strict ? "strict" : "lazy",
(iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
"(set via kernel command line)" : "");
I think it's worth mentioning "default" somewhere, as not all IOMMUs or
devices will use lazy mode even if it's default.
Thanks,
John
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] iommu: Print default strict or lazy mode at init time
2021-06-01 15:50 ` John Garry
@ 2021-06-01 16:42 ` Robin Murphy
-1 siblings, 0 replies; 10+ messages in thread
From: Robin Murphy @ 2021-06-01 16:42 UTC (permalink / raw)
To: John Garry, joro, will; +Cc: iommu, linux-kernel, hch
On 2021-06-01 16:50, John Garry wrote:
> On 01/06/2021 10:09, Robin Murphy wrote:
>>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>>> index 808ab70d5df5..f25fae62f077 100644
>>> --- a/drivers/iommu/iommu.c
>>> +++ b/drivers/iommu/iommu.c
>>> @@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
>>> (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
>>> "(set via kernel command line)" : "");
>>> + pr_info("Default DMA domain mode: %s %s\n",
>>
>> Nit: I think this might be a little unclear for end-users - *I'm* not
>> even sure whether "Default" here is meant to refer to the mode setting
>> itself or to default domains (of DMA type). Maybe something like "DMA
>> domain TLB invalidation policy"? Certainly it seems like a good idea
>> to explicitly mention invalidation to correlate with the documentation
>> of the "iommu.strict" parameter.
>>
>> Ack to the general idea though.
>
> ok, so I'll go with this:
>
> pr_info("DMA domain default TLB invalidation policy: %s mode %s\n",
> iommu_dma_strict ? "strict" : "lazy",
> (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
> "(set via kernel command line)" : "");
>
> I think it's worth mentioning "default" somewhere, as not all IOMMUs or
> devices will use lazy mode even if it's default.
But that's part of what I think is misleading - I boot and see that the
default is something, so I reboot with iommu.strict to explicitly set it
the other way, but now that's the default... huh?
The way I see it, we're saying what the current IOMMU API policy is -
the value of iommu_dma_strict at any given time is fact - but we're not
necessarily saying how widely that policy is enforced. We similarly
report the type for default domains from global policy even though that
may also be overridden per-group by drivers and/or userspace later; we
don't say it's the *default* default domain type.
However, having now debugged the AMD issue from another thread, I think
doing this at subsys_initcall is in fact going to be too early to be
meaningful, since it ignores drivers' ability to change the global policy :(
Robin.
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] iommu: Print default strict or lazy mode at init time
@ 2021-06-01 16:42 ` Robin Murphy
0 siblings, 0 replies; 10+ messages in thread
From: Robin Murphy @ 2021-06-01 16:42 UTC (permalink / raw)
To: John Garry, joro, will; +Cc: iommu, linux-kernel, hch
On 2021-06-01 16:50, John Garry wrote:
> On 01/06/2021 10:09, Robin Murphy wrote:
>>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>>> index 808ab70d5df5..f25fae62f077 100644
>>> --- a/drivers/iommu/iommu.c
>>> +++ b/drivers/iommu/iommu.c
>>> @@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
>>> (iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
>>> "(set via kernel command line)" : "");
>>> + pr_info("Default DMA domain mode: %s %s\n",
>>
>> Nit: I think this might be a little unclear for end-users - *I'm* not
>> even sure whether "Default" here is meant to refer to the mode setting
>> itself or to default domains (of DMA type). Maybe something like "DMA
>> domain TLB invalidation policy"? Certainly it seems like a good idea
>> to explicitly mention invalidation to correlate with the documentation
>> of the "iommu.strict" parameter.
>>
>> Ack to the general idea though.
>
> ok, so I'll go with this:
>
> pr_info("DMA domain default TLB invalidation policy: %s mode %s\n",
> iommu_dma_strict ? "strict" : "lazy",
> (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
> "(set via kernel command line)" : "");
>
> I think it's worth mentioning "default" somewhere, as not all IOMMUs or
> devices will use lazy mode even if it's default.
But that's part of what I think is misleading - I boot and see that the
default is something, so I reboot with iommu.strict to explicitly set it
the other way, but now that's the default... huh?
The way I see it, we're saying what the current IOMMU API policy is -
the value of iommu_dma_strict at any given time is fact - but we're not
necessarily saying how widely that policy is enforced. We similarly
report the type for default domains from global policy even though that
may also be overridden per-group by drivers and/or userspace later; we
don't say it's the *default* default domain type.
However, having now debugged the AMD issue from another thread, I think
doing this at subsys_initcall is in fact going to be too early to be
meaningful, since it ignores drivers' ability to change the global policy :(
Robin.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] iommu: Print default strict or lazy mode at init time
2021-06-01 16:42 ` Robin Murphy
@ 2021-06-01 17:44 ` John Garry
-1 siblings, 0 replies; 10+ messages in thread
From: John Garry @ 2021-06-01 17:44 UTC (permalink / raw)
To: Robin Murphy, joro, will; +Cc: iommu, linux-kernel, hch
>>
>> pr_info("DMA domain default TLB invalidation policy: %s mode %s\n",
>> iommu_dma_strict ? "strict" : "lazy",
>> (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
>> "(set via kernel command line)" : "");
>>
>> I think it's worth mentioning "default" somewhere, as not all IOMMUs
>> or devices will use lazy mode even if it's default.
>
> But that's part of what I think is misleading - I boot and see that the
> default is something, so I reboot with iommu.strict to explicitly set it
> the other way, but now that's the default... huh?
>
> The way I see it, we're saying what the current IOMMU API policy is -
> the value of iommu_dma_strict at any given time is fact - but we're not
> necessarily saying how widely that policy is enforced. We similarly
> report the type for default domains from global policy even though that
> may also be overridden per-group by drivers and/or userspace later;
> we
> don't say it's the *default* default domain type.
I think that is this is the behavior a user would understand from that
message.
However from a glance at the intel IOMMU driver, it seems possible to
change default domain type after iommu_subsys_init().
>
> However, having now debugged the AMD issue from another thread, I think
> doing this at subsys_initcall is in fact going to be too early to be
> meaningful, since it ignores drivers' ability to change the global
> policy :(
A user may still learn the IOMMU group domain type from sysfs. There is
no such thing for TLB invalidation mode - how about add a file for this?
It would be useful.
Thanks,
John
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] iommu: Print default strict or lazy mode at init time
@ 2021-06-01 17:44 ` John Garry
0 siblings, 0 replies; 10+ messages in thread
From: John Garry @ 2021-06-01 17:44 UTC (permalink / raw)
To: Robin Murphy, joro, will; +Cc: iommu, linux-kernel, hch
>>
>> pr_info("DMA domain default TLB invalidation policy: %s mode %s\n",
>> iommu_dma_strict ? "strict" : "lazy",
>> (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
>> "(set via kernel command line)" : "");
>>
>> I think it's worth mentioning "default" somewhere, as not all IOMMUs
>> or devices will use lazy mode even if it's default.
>
> But that's part of what I think is misleading - I boot and see that the
> default is something, so I reboot with iommu.strict to explicitly set it
> the other way, but now that's the default... huh?
>
> The way I see it, we're saying what the current IOMMU API policy is -
> the value of iommu_dma_strict at any given time is fact - but we're not
> necessarily saying how widely that policy is enforced. We similarly
> report the type for default domains from global policy even though that
> may also be overridden per-group by drivers and/or userspace later;
> we
> don't say it's the *default* default domain type.
I think that is this is the behavior a user would understand from that
message.
However from a glance at the intel IOMMU driver, it seems possible to
change default domain type after iommu_subsys_init().
>
> However, having now debugged the AMD issue from another thread, I think
> doing this at subsys_initcall is in fact going to be too early to be
> meaningful, since it ignores drivers' ability to change the global
> policy :(
A user may still learn the IOMMU group domain type from sysfs. There is
no such thing for TLB invalidation mode - how about add a file for this?
It would be useful.
Thanks,
John
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2021-06-01 17:45 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-05-28 13:37 [PATCH] iommu: Print default strict or lazy mode at init time John Garry
2021-05-28 13:37 ` John Garry
2021-06-01 9:09 ` Robin Murphy
2021-06-01 9:09 ` Robin Murphy
2021-06-01 15:50 ` John Garry
2021-06-01 15:50 ` John Garry
2021-06-01 16:42 ` Robin Murphy
2021-06-01 16:42 ` Robin Murphy
2021-06-01 17:44 ` John Garry
2021-06-01 17:44 ` John Garry
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.