Re: [PATCH 2/2] iommu/amd: Handle PPR log overflow

[Joao Martins <joao.m.martins@oracle.com>]

On 09/06/2023 11:17, Vasant Hegde wrote:
> Some ATS-capable peripherals can issue requests to the processor to service
> peripheral page requests using PCIe PRI (the Page Request Interface). IOMMU
> supports PRI using PPR log buffer. IOMMU writes PRI request to PPR log
> buffer and sends PPR interrupt to host. When there is no space in the
> PPR log buffer (PPR log overflow) it will set PprOverflow bit in 'MMIO
> Offset 2020h IOMMU Status Register'. When this happens PPR log needs to be
> restarted as specified in IOMMU spec [1] section 2.6.2.
> 
> When handling the event it just resumes the PPR log without resizing
> (similar to the way event and GA log overflow is handled).
> 
> Failing to handle PPR overflow means device may not work properly as
> IOMMU stops processing new PPR events from device.
> 
> [1] https://www.amd.com/system/files/TechDocs/48882_3.07_PUB.pdf
> 
> Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>

Reviewed-by: Joao Martins <joao.m.martins@oracle.com>

> ---
>  drivers/iommu/amd/amd_iommu.h       |  1 +
>  drivers/iommu/amd/amd_iommu_types.h |  2 ++
>  drivers/iommu/amd/init.c            | 11 +++++++++++
>  drivers/iommu/amd/iommu.c           |  9 ++++++++-
>  4 files changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
> index 317d5c26c614..156f57b4f78c 100644
> --- a/drivers/iommu/amd/amd_iommu.h
> +++ b/drivers/iommu/amd/amd_iommu.h
> @@ -16,6 +16,7 @@ irqreturn_t amd_iommu_int_handler(int irq, void *data);
>  void amd_iommu_apply_erratum_63(struct amd_iommu *iommu, u16 devid);
>  void amd_iommu_restart_event_logging(struct amd_iommu *iommu);
>  void amd_iommu_restart_ga_log(struct amd_iommu *iommu);
> +void amd_iommu_restart_ppr_log(struct amd_iommu *iommu);
>  void amd_iommu_set_rlookup_table(struct amd_iommu *iommu, u16 devid);
>  
>  #ifdef CONFIG_AMD_IOMMU_DEBUGFS
> diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
> index 318b84cf47f6..a993e1bdb70b 100644
> --- a/drivers/iommu/amd/amd_iommu_types.h
> +++ b/drivers/iommu/amd/amd_iommu_types.h
> @@ -124,7 +124,9 @@
>  #define MMIO_STATUS_EVT_INT_MASK		BIT(1)
>  #define MMIO_STATUS_COM_WAIT_INT_MASK		BIT(2)
>  #define MMIO_STATUS_EVT_RUN_MASK		BIT(3)
> +#define MMIO_STATUS_PPR_OVERFLOW_MASK		BIT(5)
>  #define MMIO_STATUS_PPR_INT_MASK		BIT(6)
> +#define MMIO_STATUS_PPR_RUN_MASK		BIT(7)
>  #define MMIO_STATUS_GALOG_RUN_MASK		BIT(8)
>  #define MMIO_STATUS_GALOG_OVERFLOW_MASK		BIT(9)
>  #define MMIO_STATUS_GALOG_INT_MASK		BIT(10)
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index 3c21e9333899..9908cd4f1c31 100644
> --- a/drivers/iommu/amd/init.c
> +++ b/drivers/iommu/amd/init.c
> @@ -795,6 +795,17 @@ void amd_iommu_restart_ga_log(struct amd_iommu *iommu)
>  			      MMIO_STATUS_GALOG_OVERFLOW_MASK);
>  }
>  
> +/*
> + * This function restarts ppr logging in case the IOMMU experienced
> + * PPR log overflow.
> + */
> +void amd_iommu_restart_ppr_log(struct amd_iommu *iommu)
> +{
> +	amd_iommu_restart_log(iommu, "PPR", CONTROL_PPRINT_EN,
> +			      CONTROL_PPRLOG_EN, MMIO_STATUS_PPR_RUN_MASK,
> +			      MMIO_STATUS_PPR_OVERFLOW_MASK);
> +}
> +
>  /*
>   * This function resets the command buffer if the IOMMU stopped fetching
>   * commands from it.
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index a29548d98b6a..3c179d548ecd 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -844,6 +844,7 @@ amd_iommu_set_pci_msi_domain(struct device *dev, struct amd_iommu *iommu) { }
>  #define AMD_IOMMU_INT_MASK	\
>  	(MMIO_STATUS_EVT_OVERFLOW_MASK | \
>  	 MMIO_STATUS_EVT_INT_MASK | \
> +	 MMIO_STATUS_PPR_OVERFLOW_MASK | \
>  	 MMIO_STATUS_PPR_INT_MASK | \
>  	 MMIO_STATUS_GALOG_OVERFLOW_MASK | \
>  	 MMIO_STATUS_GALOG_INT_MASK)
> @@ -863,11 +864,17 @@ irqreturn_t amd_iommu_int_thread(int irq, void *data)
>  			iommu_poll_events(iommu);
>  		}
>  
> -		if (status & MMIO_STATUS_PPR_INT_MASK) {
> +		if (status & (MMIO_STATUS_PPR_INT_MASK |
> +			      MMIO_STATUS_PPR_OVERFLOW_MASK)) {
>  			pr_devel("Processing IOMMU PPR Log\n");
>  			iommu_poll_ppr_log(iommu);
>  		}
>  
> +		if (status & MMIO_STATUS_PPR_OVERFLOW_MASK) {
> +			pr_info_ratelimited("IOMMU PPR log overflow\n");
> +			amd_iommu_restart_ppr_log(iommu);
> +		}
> +
>  #ifdef CONFIG_IRQ_REMAP
>  		if (status & (MMIO_STATUS_GALOG_INT_MASK |
>  			      MMIO_STATUS_GALOG_OVERFLOW_MASK)) {