diff mbox series

[v2,11/13] iommu/vt-d: Make posted MSI an opt-in cmdline option

Message ID 20240405223110.1609888-12-jacob.jun.pan@linux.intel.com (mailing list archive)
State New, archived
Headers show
Series Coalesced Interrupt Delivery with posted MSI | expand

Commit Message

Jacob Pan April 5, 2024, 10:31 p.m. UTC
Add a command line opt-in option for posted MSI if CONFIG_X86_POSTED_MSI=y.

Also introduce a helper function for testing if posted MSI is supported on
the platform.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  1 +
 arch/x86/include/asm/irq_remapping.h            | 11 +++++++++++
 drivers/iommu/irq_remapping.c                   | 13 ++++++++++++-
 3 files changed, 24 insertions(+), 1 deletion(-)

Comments

Robert Hoo April 6, 2024, 4:31 a.m. UTC | #1
On 4/6/2024 6:31 AM, Jacob Pan wrote:
> Add a command line opt-in option for posted MSI if CONFIG_X86_POSTED_MSI=y.
> 
> Also introduce a helper function for testing if posted MSI is supported on
> the platform.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
>   Documentation/admin-guide/kernel-parameters.txt |  1 +
>   arch/x86/include/asm/irq_remapping.h            | 11 +++++++++++
>   drivers/iommu/irq_remapping.c                   | 13 ++++++++++++-
>   3 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index bb884c14b2f6..e5fd02423c4c 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2251,6 +2251,7 @@
>   			no_x2apic_optout
>   				BIOS x2APIC opt-out request will be ignored
>   			nopost	disable Interrupt Posting
> +			posted_msi enable MSIs delivered as posted interrupts
>   
>   	iomem=		Disable strict checking of access to MMIO memory
>   		strict	regions from userspace.
> diff --git a/arch/x86/include/asm/irq_remapping.h b/arch/x86/include/asm/irq_remapping.h
> index 7a2ed154a5e1..e46bde61029b 100644
> --- a/arch/x86/include/asm/irq_remapping.h
> +++ b/arch/x86/include/asm/irq_remapping.h
> @@ -50,6 +50,17 @@ static inline struct irq_domain *arch_get_ir_parent_domain(void)
>   	return x86_vector_domain;
>   }
>   
> +#ifdef CONFIG_X86_POSTED_MSI
> +extern int enable_posted_msi;
> +
> +static inline bool posted_msi_supported(void)
> +{
> +	return enable_posted_msi && irq_remapping_cap(IRQ_POSTING_CAP);
> +}

Out of this patch set's scope, but, dropping into irq_remappping_cap(), I'd like 
to bring this change for discussion:

diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
index 4047ac396728..ef2de9034897 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -98,7 +98,7 @@ void set_irq_remapping_broken(void)

  bool irq_remapping_cap(enum irq_remap_cap cap)
  {
-       if (!remap_ops || disable_irq_post)
+       if (!remap_ops || disable_irq_remap)
                 return false;

         return (remap_ops->capability & (1 << cap));


1. irq_remapping_cap() is to exam some cap, though at present it has only 1 cap, 
i.e. IRQ_POSTING_CAP, simply return false just because of disable_irq_post isn't 
good. Instead, IRQ_REMAP is the foundation of all remapping caps.
2. disable_irq_post is used by Intel iommu code only, here irq_remapping_cap() 
is common code. e.g. AMD iommu code doesn't use it to judge set cap of irq_post 
or not.

> +#else
> +static inline bool posted_msi_supported(void) { return false; };
> +#endif
Jacob Pan April 8, 2024, 11:33 p.m. UTC | #2
Hi Robert,

On Sat, 6 Apr 2024 12:31:14 +0800, Robert Hoo <robert.hoo.linux@gmail.com>
wrote:

> On 4/6/2024 6:31 AM, Jacob Pan wrote:
> > Add a command line opt-in option for posted MSI if
> > CONFIG_X86_POSTED_MSI=y.
> > 
> > Also introduce a helper function for testing if posted MSI is supported
> > on the platform.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> >   Documentation/admin-guide/kernel-parameters.txt |  1 +
> >   arch/x86/include/asm/irq_remapping.h            | 11 +++++++++++
> >   drivers/iommu/irq_remapping.c                   | 13 ++++++++++++-
> >   3 files changed, 24 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt
> > b/Documentation/admin-guide/kernel-parameters.txt index
> > bb884c14b2f6..e5fd02423c4c 100644 ---
> > a/Documentation/admin-guide/kernel-parameters.txt +++
> > b/Documentation/admin-guide/kernel-parameters.txt @@ -2251,6 +2251,7 @@
> >   			no_x2apic_optout
> >   				BIOS x2APIC opt-out request will be
> > ignored nopost	disable Interrupt Posting
> > +			posted_msi enable MSIs delivered as posted
> > interrupts 
> >   	iomem=		Disable strict checking of access to
> > MMIO memory strict	regions from userspace.
> > diff --git a/arch/x86/include/asm/irq_remapping.h
> > b/arch/x86/include/asm/irq_remapping.h index 7a2ed154a5e1..e46bde61029b
> > 100644 --- a/arch/x86/include/asm/irq_remapping.h
> > +++ b/arch/x86/include/asm/irq_remapping.h
> > @@ -50,6 +50,17 @@ static inline struct irq_domain
> > *arch_get_ir_parent_domain(void) return x86_vector_domain;
> >   }
> >   
> > +#ifdef CONFIG_X86_POSTED_MSI
> > +extern int enable_posted_msi;
> > +
> > +static inline bool posted_msi_supported(void)
> > +{
> > +	return enable_posted_msi && irq_remapping_cap(IRQ_POSTING_CAP);
> > +}  
> 
> Out of this patch set's scope, but, dropping into irq_remappping_cap(),
> I'd like to bring this change for discussion:
> 
> diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
> index 4047ac396728..ef2de9034897 100644
> --- a/drivers/iommu/irq_remapping.c
> +++ b/drivers/iommu/irq_remapping.c
> @@ -98,7 +98,7 @@ void set_irq_remapping_broken(void)
> 
>   bool irq_remapping_cap(enum irq_remap_cap cap)
>   {
> -       if (!remap_ops || disable_irq_post)
> +       if (!remap_ops || disable_irq_remap)
>                  return false;
> 
>          return (remap_ops->capability & (1 << cap));
> 
> 
> 1. irq_remapping_cap() is to exam some cap, though at present it has only
> 1 cap, i.e. IRQ_POSTING_CAP, simply return false just because of
> disable_irq_post isn't good. Instead, IRQ_REMAP is the foundation of all
> remapping caps. 2. disable_irq_post is used by Intel iommu code only,
> here irq_remapping_cap() is common code. e.g. AMD iommu code doesn't use
> it to judge set cap of irq_post or not.
I agree, posting should be treated as a sub-capability of remapping.
IRQ_POSTING_CAP is only set when remapping is on.

We need to delete this such that posting is always off when remapping is
off.

--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -1038,11 +1038,7 @@ static void disable_irq_remapping(void)
                iommu_disable_irq_remapping(iommu);
        }
 
-       /*
-        * Clear Posted-Interrupts capability.
-        */
-       if (!disable_irq_post)
-               intel_irq_remap_ops.capability &= ~(1 << IRQ_POSTING_CAP);
+       intel_irq_remap_ops.capability &= ~(1 << IRQ_POSTING_CAP);
 } 

> > +#else
> > +static inline bool posted_msi_supported(void) { return false; };
> > +#endif  
> 


Thanks,

Jacob
Tian, Kevin April 12, 2024, 9:31 a.m. UTC | #3
> From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Sent: Saturday, April 6, 2024 6:31 AM
> 
> +#ifdef CONFIG_X86_POSTED_MSI
> +		else if (!strncmp(str, "posted_msi", 10)) {
> +			if (disable_irq_post || disable_irq_remap)
> +				pr_warn("Posted MSI not enabled due to
> conflicting options!");
> +			else
> +				enable_posted_msi = 1;
> +		}
> +#endif

the check of disable_irq_remap is unnecessary. It's unlikely to have
a configuration with disable_irq_post=0 while disable_irq_remap=1
given the latter has bigger scope.

but thinking more do we really need a check here? there is no order
guarantee that "posted_msi" is parsed after the parameters deciding
the value of two disable variables.

it probably makes more sense to just set enable_posted_msi here
and then do all required checks when picking up the irqchip in
intel_irq_remapping_alloc().
Robert Hoo April 13, 2024, 10:59 a.m. UTC | #4
On 4/9/2024 7:33 AM, Jacob Pan wrote:
> Hi Robert,
> 
> On Sat, 6 Apr 2024 12:31:14 +0800, Robert Hoo <robert.hoo.linux@gmail.com>
> wrote:
> 
>> On 4/6/2024 6:31 AM, Jacob Pan wrote:
>>> Add a command line opt-in option for posted MSI if
>>> CONFIG_X86_POSTED_MSI=y.
>>>
>>> Also introduce a helper function for testing if posted MSI is supported
>>> on the platform.
>>>
>>> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
>>> ---
>>>    Documentation/admin-guide/kernel-parameters.txt |  1 +
>>>    arch/x86/include/asm/irq_remapping.h            | 11 +++++++++++
>>>    drivers/iommu/irq_remapping.c                   | 13 ++++++++++++-
>>>    3 files changed, 24 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt
>>> b/Documentation/admin-guide/kernel-parameters.txt index
>>> bb884c14b2f6..e5fd02423c4c 100644 ---
>>> a/Documentation/admin-guide/kernel-parameters.txt +++
>>> b/Documentation/admin-guide/kernel-parameters.txt @@ -2251,6 +2251,7 @@
>>>    			no_x2apic_optout
>>>    				BIOS x2APIC opt-out request will be
>>> ignored nopost	disable Interrupt Posting
>>> +			posted_msi enable MSIs delivered as posted
>>> interrupts
>>>    	iomem=		Disable strict checking of access to
>>> MMIO memory strict	regions from userspace.
>>> diff --git a/arch/x86/include/asm/irq_remapping.h
>>> b/arch/x86/include/asm/irq_remapping.h index 7a2ed154a5e1..e46bde61029b
>>> 100644 --- a/arch/x86/include/asm/irq_remapping.h
>>> +++ b/arch/x86/include/asm/irq_remapping.h
>>> @@ -50,6 +50,17 @@ static inline struct irq_domain
>>> *arch_get_ir_parent_domain(void) return x86_vector_domain;
>>>    }
>>>    
>>> +#ifdef CONFIG_X86_POSTED_MSI
>>> +extern int enable_posted_msi;
>>> +
>>> +static inline bool posted_msi_supported(void)
>>> +{
>>> +	return enable_posted_msi && irq_remapping_cap(IRQ_POSTING_CAP);
>>> +}
>>
>> Out of this patch set's scope, but, dropping into irq_remappping_cap(),
>> I'd like to bring this change for discussion:
>>
>> diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
>> index 4047ac396728..ef2de9034897 100644
>> --- a/drivers/iommu/irq_remapping.c
>> +++ b/drivers/iommu/irq_remapping.c
>> @@ -98,7 +98,7 @@ void set_irq_remapping_broken(void)
>>
>>    bool irq_remapping_cap(enum irq_remap_cap cap)
>>    {
>> -       if (!remap_ops || disable_irq_post)
>> +       if (!remap_ops || disable_irq_remap)
>>                   return false;
>>
>>           return (remap_ops->capability & (1 << cap));
>>
>>
>> 1. irq_remapping_cap() is to exam some cap, though at present it has only
>> 1 cap, i.e. IRQ_POSTING_CAP, simply return false just because of
>> disable_irq_post isn't good. Instead, IRQ_REMAP is the foundation of all
>> remapping caps. 2. disable_irq_post is used by Intel iommu code only,
>> here irq_remapping_cap() is common code. e.g. AMD iommu code doesn't use
>> it to judge set cap of irq_post or not.
> I agree, posting should be treated as a sub-capability of remapping.
> IRQ_POSTING_CAP is only set when remapping is on.
> 
> We need to delete this such that posting is always off when remapping is
> off.
> 
> --- a/drivers/iommu/intel/irq_remapping.c
> +++ b/drivers/iommu/intel/irq_remapping.c
> @@ -1038,11 +1038,7 @@ static void disable_irq_remapping(void)
>                  iommu_disable_irq_remapping(iommu);
>          }
>   
> -       /*
> -        * Clear Posted-Interrupts capability.
> -        */
> -       if (!disable_irq_post)
> -               intel_irq_remap_ops.capability &= ~(1 << IRQ_POSTING_CAP);
> +       intel_irq_remap_ops.capability &= ~(1 << IRQ_POSTING_CAP);
>   }
> 
Right.
Jacob Pan April 15, 2024, 11:20 p.m. UTC | #5
Hi Kevin,

On Fri, 12 Apr 2024 09:31:32 +0000, "Tian, Kevin" <kevin.tian@intel.com>
wrote:

> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Sent: Saturday, April 6, 2024 6:31 AM
> > 
> > +#ifdef CONFIG_X86_POSTED_MSI
> > +		else if (!strncmp(str, "posted_msi", 10)) {
> > +			if (disable_irq_post || disable_irq_remap)
> > +				pr_warn("Posted MSI not enabled due to
> > conflicting options!");
> > +			else
> > +				enable_posted_msi = 1;
> > +		}
> > +#endif  
> 
> the check of disable_irq_remap is unnecessary. It's unlikely to have
> a configuration with disable_irq_post=0 while disable_irq_remap=1
> given the latter has bigger scope.
> 
> but thinking more do we really need a check here? there is no order
> guarantee that "posted_msi" is parsed after the parameters deciding
> the value of two disable variables.
> 
> it probably makes more sense to just set enable_posted_msi here
> and then do all required checks when picking up the irqchip in
> intel_irq_remapping_alloc().

Makes sense, I have a helper function posted_msi_supported() called in
intel_irq_remapping_alloc() already.

My intention was to alert negligent users, but is is not really necessary
as you said.

Thanks,

Jacob
diff mbox series

Patch

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bb884c14b2f6..e5fd02423c4c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2251,6 +2251,7 @@ 
 			no_x2apic_optout
 				BIOS x2APIC opt-out request will be ignored
 			nopost	disable Interrupt Posting
+			posted_msi enable MSIs delivered as posted interrupts
 
 	iomem=		Disable strict checking of access to MMIO memory
 		strict	regions from userspace.
diff --git a/arch/x86/include/asm/irq_remapping.h b/arch/x86/include/asm/irq_remapping.h
index 7a2ed154a5e1..e46bde61029b 100644
--- a/arch/x86/include/asm/irq_remapping.h
+++ b/arch/x86/include/asm/irq_remapping.h
@@ -50,6 +50,17 @@  static inline struct irq_domain *arch_get_ir_parent_domain(void)
 	return x86_vector_domain;
 }
 
+#ifdef CONFIG_X86_POSTED_MSI
+extern int enable_posted_msi;
+
+static inline bool posted_msi_supported(void)
+{
+	return enable_posted_msi && irq_remapping_cap(IRQ_POSTING_CAP);
+}
+#else
+static inline bool posted_msi_supported(void) { return false; };
+#endif
+
 #else  /* CONFIG_IRQ_REMAP */
 
 static inline bool irq_remapping_cap(enum irq_remap_cap cap) { return 0; }
diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
index ee59647c2050..5672783c9f1f 100644
--- a/drivers/iommu/irq_remapping.c
+++ b/drivers/iommu/irq_remapping.c
@@ -24,6 +24,10 @@  int no_x2apic_optout;
 
 int disable_irq_post = 0;
 
+#ifdef CONFIG_X86_POSTED_MSI
+int enable_posted_msi;
+#endif
+
 static int disable_irq_remap;
 static struct irq_remap_ops *remap_ops;
 
@@ -70,7 +74,14 @@  static __init int setup_irqremap(char *str)
 			no_x2apic_optout = 1;
 		else if (!strncmp(str, "nopost", 6))
 			disable_irq_post = 1;
-
+#ifdef CONFIG_X86_POSTED_MSI
+		else if (!strncmp(str, "posted_msi", 10)) {
+			if (disable_irq_post || disable_irq_remap)
+				pr_warn("Posted MSI not enabled due to conflicting options!");
+			else
+				enable_posted_msi = 1;
+		}
+#endif
 		str += strcspn(str, ",");
 		while (*str == ',')
 			str++;