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[PATCH 09/10] iommu/ipmmu-vmsa: Use refcount for the micro-TLBs

Oleksandr Tyshchenko posted 10 patches 3 years ago
There is a newer version of this series
[PATCH 09/10] iommu/ipmmu-vmsa: Use refcount for the micro-TLBs
Posted by Oleksandr Tyshchenko 3 years ago 
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

Reference-count the micro-TLBs as several bus masters can be
connected to the same micro-TLB (and drop TODO comment).
This wasn't an issue so far, since the platform devices
(this driver deals with) get assigned/deassigned together during
domain creation/destruction. But, in order to support PCI devices
(which are hot-pluggable) in the near future we will need to
take care of.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
---
 xen/drivers/passthrough/arm/ipmmu-vmsa.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/xen/drivers/passthrough/arm/ipmmu-vmsa.c b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
index 22dd84e..32609f8 100644
--- a/xen/drivers/passthrough/arm/ipmmu-vmsa.c
+++ b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
@@ -134,6 +134,7 @@ struct ipmmu_vmsa_device {
     spinlock_t lock;    /* Protects ctx and domains[] */
     DECLARE_BITMAP(ctx, IPMMU_CTX_MAX);
     struct ipmmu_vmsa_domain *domains[IPMMU_CTX_MAX];
+    unsigned int utlb_refcount[IPMMU_UTLB_MAX];
     const struct ipmmu_features *features;
 };
 
@@ -477,13 +478,12 @@ static int ipmmu_utlb_enable(struct ipmmu_vmsa_domain *domain,
         }
     }
 
-    /*
-     * TODO: Reference-count the micro-TLB as several bus masters can be
-     * connected to the same micro-TLB.
-     */
-    ipmmu_imuasid_write(mmu, utlb, 0);
-    ipmmu_imuctr_write(mmu, utlb, imuctr |
-                       IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN);
+    if ( mmu->utlb_refcount[utlb]++ == 0 )
+    {
+        ipmmu_imuasid_write(mmu, utlb, 0);
+        ipmmu_imuctr_write(mmu, utlb, imuctr |
+                           IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN);
+    }
 
     return 0;
 }
@@ -494,7 +494,8 @@ static void ipmmu_utlb_disable(struct ipmmu_vmsa_domain *domain,
 {
     struct ipmmu_vmsa_device *mmu = domain->mmu;
 
-    ipmmu_imuctr_write(mmu, utlb, 0);
+    if ( --mmu->utlb_refcount[utlb] == 0 )
+        ipmmu_imuctr_write(mmu, utlb, 0);
 }
 
 /* Domain/Context Management */
-- 
2.7.4
Re: [PATCH 09/10] iommu/ipmmu-vmsa: Use refcount for the micro-TLBs
Posted by Volodymyr Babchuk 2 years, 11 months ago 
Hi Oleksandr,


Oleksandr Tyshchenko <olekstysh@gmail.com> writes:

> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>
> Reference-count the micro-TLBs as several bus masters can be
> connected to the same micro-TLB (and drop TODO comment).
> This wasn't an issue so far, since the platform devices
> (this driver deals with) get assigned/deassigned together during
> domain creation/destruction. But, in order to support PCI devices
> (which are hot-pluggable) in the near future we will need to
> take care of.
>
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> ---
>  xen/drivers/passthrough/arm/ipmmu-vmsa.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/xen/drivers/passthrough/arm/ipmmu-vmsa.c b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> index 22dd84e..32609f8 100644
> --- a/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> +++ b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> @@ -134,6 +134,7 @@ struct ipmmu_vmsa_device {
>      spinlock_t lock;    /* Protects ctx and domains[] */
>      DECLARE_BITMAP(ctx, IPMMU_CTX_MAX);
>      struct ipmmu_vmsa_domain *domains[IPMMU_CTX_MAX];
> +    unsigned int utlb_refcount[IPMMU_UTLB_MAX];
>      const struct ipmmu_features *features;
>  };
>  
> @@ -477,13 +478,12 @@ static int ipmmu_utlb_enable(struct ipmmu_vmsa_domain *domain,
>          }
>      }
>  
> -    /*
> -     * TODO: Reference-count the micro-TLB as several bus masters can be
> -     * connected to the same micro-TLB.
> -     */
> -    ipmmu_imuasid_write(mmu, utlb, 0);
> -    ipmmu_imuctr_write(mmu, utlb, imuctr |
> -                       IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN);
> +    if ( mmu->utlb_refcount[utlb]++ == 0 )
> +    {
> +        ipmmu_imuasid_write(mmu, utlb, 0);
> +        ipmmu_imuctr_write(mmu, utlb, imuctr |
> +                           IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN);
> +    }
>  
>      return 0;
>  }
> @@ -494,7 +494,8 @@ static void ipmmu_utlb_disable(struct ipmmu_vmsa_domain *domain,
>  {
>      struct ipmmu_vmsa_device *mmu = domain->mmu;
>  
> -    ipmmu_imuctr_write(mmu, utlb, 0);

It would be great to have

+      ASSERT(mmu->utlb_refcount[utlb] > 0);

there. Just in case.

> +    if ( --mmu->utlb_refcount[utlb] == 0 )
> +        ipmmu_imuctr_write(mmu, utlb, 0);
>  }
>  
>  /* Domain/Context Management */


-- 
Volodymyr Babchuk at EPAM
Re: [PATCH 09/10] iommu/ipmmu-vmsa: Use refcount for the micro-TLBs
Posted by Oleksandr 2 years, 11 months ago 
On 15.12.21 04:58, Volodymyr Babchuk wrote:
> Hi Oleksandr,

Hi Volodymyr


>
>
> Oleksandr Tyshchenko <olekstysh@gmail.com> writes:
>
>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>>
>> Reference-count the micro-TLBs as several bus masters can be
>> connected to the same micro-TLB (and drop TODO comment).
>> This wasn't an issue so far, since the platform devices
>> (this driver deals with) get assigned/deassigned together during
>> domain creation/destruction. But, in order to support PCI devices
>> (which are hot-pluggable) in the near future we will need to
>> take care of.
>>
>> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>> ---
>>   xen/drivers/passthrough/arm/ipmmu-vmsa.c | 17 +++++++++--------
>>   1 file changed, 9 insertions(+), 8 deletions(-)
>>
>> diff --git a/xen/drivers/passthrough/arm/ipmmu-vmsa.c b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
>> index 22dd84e..32609f8 100644
>> --- a/xen/drivers/passthrough/arm/ipmmu-vmsa.c
>> +++ b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
>> @@ -134,6 +134,7 @@ struct ipmmu_vmsa_device {
>>       spinlock_t lock;    /* Protects ctx and domains[] */
>>       DECLARE_BITMAP(ctx, IPMMU_CTX_MAX);
>>       struct ipmmu_vmsa_domain *domains[IPMMU_CTX_MAX];
>> +    unsigned int utlb_refcount[IPMMU_UTLB_MAX];
>>       const struct ipmmu_features *features;
>>   };
>>   
>> @@ -477,13 +478,12 @@ static int ipmmu_utlb_enable(struct ipmmu_vmsa_domain *domain,
>>           }
>>       }
>>   
>> -    /*
>> -     * TODO: Reference-count the micro-TLB as several bus masters can be
>> -     * connected to the same micro-TLB.
>> -     */
>> -    ipmmu_imuasid_write(mmu, utlb, 0);
>> -    ipmmu_imuctr_write(mmu, utlb, imuctr |
>> -                       IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN);
>> +    if ( mmu->utlb_refcount[utlb]++ == 0 )
>> +    {
>> +        ipmmu_imuasid_write(mmu, utlb, 0);
>> +        ipmmu_imuctr_write(mmu, utlb, imuctr |
>> +                           IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN);
>> +    }
>>   
>>       return 0;
>>   }
>> @@ -494,7 +494,8 @@ static void ipmmu_utlb_disable(struct ipmmu_vmsa_domain *domain,
>>   {
>>       struct ipmmu_vmsa_device *mmu = domain->mmu;
>>   
>> -    ipmmu_imuctr_write(mmu, utlb, 0);
> It would be great to have
>
> +      ASSERT(mmu->utlb_refcount[utlb] > 0);
>
> there. Just in case.

ok, will add.


Thank you.


>
>> +    if ( --mmu->utlb_refcount[utlb] == 0 )
>> +        ipmmu_imuctr_write(mmu, utlb, 0);
>>   }
>>   
>>   /* Domain/Context Management */
>
-- 
Regards,

Oleksandr Tyshchenko
RE: [PATCH 09/10] iommu/ipmmu-vmsa: Use refcount for the micro-TLBs
Posted by Yoshihiro Shimoda 2 years, 11 months ago 
Hello Oleksandr-san,

Thank you for the patch!

> From: Oleksandr Tyshchenko, Sent: Sunday, November 28, 2021 2:52 AM
> 
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> Reference-count the micro-TLBs as several bus masters can be
> connected to the same micro-TLB (and drop TODO comment).
> This wasn't an issue so far, since the platform devices
> (this driver deals with) get assigned/deassigned together during
> domain creation/destruction. But, in order to support PCI devices
> (which are hot-pluggable) in the near future we will need to
> take care of.
> 
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> ---
>  xen/drivers/passthrough/arm/ipmmu-vmsa.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/arm/ipmmu-vmsa.c b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> index 22dd84e..32609f8 100644
> --- a/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> +++ b/xen/drivers/passthrough/arm/ipmmu-vmsa.c
> @@ -134,6 +134,7 @@ struct ipmmu_vmsa_device {
>      spinlock_t lock;    /* Protects ctx and domains[] */
>      DECLARE_BITMAP(ctx, IPMMU_CTX_MAX);
>      struct ipmmu_vmsa_domain *domains[IPMMU_CTX_MAX];
> +    unsigned int utlb_refcount[IPMMU_UTLB_MAX];
>      const struct ipmmu_features *features;
>  };
> 
> @@ -477,13 +478,12 @@ static int ipmmu_utlb_enable(struct ipmmu_vmsa_domain *domain,
>          }
>      }
> 
> -    /*
> -     * TODO: Reference-count the micro-TLB as several bus masters can be
> -     * connected to the same micro-TLB.
> -     */
> -    ipmmu_imuasid_write(mmu, utlb, 0);
> -    ipmmu_imuctr_write(mmu, utlb, imuctr |
> -                       IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN);
> +    if ( mmu->utlb_refcount[utlb]++ == 0 )
> +    {
> +        ipmmu_imuasid_write(mmu, utlb, 0);
> +        ipmmu_imuctr_write(mmu, utlb, imuctr |
> +                           IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN);
> +    }
> 
>      return 0;
>  }
> @@ -494,7 +494,8 @@ static void ipmmu_utlb_disable(struct ipmmu_vmsa_domain *domain,
>  {
>      struct ipmmu_vmsa_device *mmu = domain->mmu;
> 
> -    ipmmu_imuctr_write(mmu, utlb, 0);

As Volodymyr-san mentioned before, after we added ASSERT(),

Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>

Best regards,
Yoshihiro Shimoda

Patchew 2.1-devel-b67e4c2

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