linux-kernel - Re: [PATCH] s390/pci: Fix reset of IOMMU software counters

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Date:   Wed, 4 Oct 2023 11:24:31 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Niklas Schnelle <schnelle@...ux.ibm.com>,
        Robin Murphy <robin.murphy@....com>,
        Gerd Bayer <gbayer@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Joerg Roedel <jroedel@...e.de>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux.dev
Subject: Re: [PATCH] s390/pci: Fix reset of IOMMU software counters

On 10/4/23 4:56 AM, Niklas Schnelle wrote:
> Together with enabling the Function Measurement Block
> zpci_fmb_enable_device() also resets the software counters. This allows
> to use "echo 0 > /sys/kernel/debug/pci/<dev>/statistics" followed by
> echo "1 > /../statistics" to reset all counters. In commit c76c067e488c
> ("s390/pci: Use dma-iommu layer") this use of the now obsolete counters
> in struct zpci_device was missed as was their removal. Fix this by
> resetting the new counters and removing the old ones.
> 
> Fixes: c76c067e488c ("s390/pci: Use dma-iommu layer")
> Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>

Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>

Verified that I could reproduce the initial issue + tested the fix using NVMe and mlx devices

> ---
> Note: This is based on and references commit IDs from Joerg Roedel's
> iommu/next branch and should go in via the iommu tree.
> ---
>  arch/s390/include/asm/pci.h |  4 ----
>  arch/s390/pci/pci.c         | 13 ++++++++++---
>  2 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 3f74f1cf37df..e91cd6bbc330 100644
> --- a/arch/s390/include/asm/pci.h
> +++ b/arch/s390/include/asm/pci.h
> @@ -173,10 +173,6 @@ struct zpci_dev {
>  	struct zpci_fmb *fmb;
>  	u16		fmb_update;	/* update interval */
>  	u16		fmb_length;
> -	/* software counters */
> -	atomic64_t allocated_pages;
> -	atomic64_t mapped_pages;
> -	atomic64_t unmapped_pages;
>  
>  	u8		version;
>  	enum pci_bus_speed max_bus_speed;
> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
> index 563cb72d9ed0..63fd9e1d9f22 100644
> --- a/arch/s390/pci/pci.c
> +++ b/arch/s390/pci/pci.c
> @@ -157,6 +157,7 @@ int zpci_unregister_ioat(struct zpci_dev *zdev, u8 dmaas)
>  int zpci_fmb_enable_device(struct zpci_dev *zdev)
>  {
>  	u64 req = ZPCI_CREATE_REQ(zdev->fh, 0, ZPCI_MOD_FC_SET_MEASURE);
> +	struct zpci_iommu_ctrs *ctrs;
>  	struct zpci_fib fib = {0};
>  	u8 cc, status;
>  
> @@ -169,9 +170,15 @@ int zpci_fmb_enable_device(struct zpci_dev *zdev)
>  	WARN_ON((u64) zdev->fmb & 0xf);
>  
>  	/* reset software counters */
> -	atomic64_set(&zdev->allocated_pages, 0);
> -	atomic64_set(&zdev->mapped_pages, 0);
> -	atomic64_set(&zdev->unmapped_pages, 0);
> +	ctrs = zpci_get_iommu_ctrs(zdev);
> +	if (ctrs) {
> +		atomic64_set(&ctrs->mapped_pages, 0);
> +		atomic64_set(&ctrs->unmapped_pages, 0);
> +		atomic64_set(&ctrs->global_rpcits, 0);
> +		atomic64_set(&ctrs->sync_map_rpcits, 0);
> +		atomic64_set(&ctrs->sync_rpcits, 0);
> +	}
> +
>  
>  	fib.fmb_addr = virt_to_phys(zdev->fmb);
>  	fib.gd = zdev->gisa;
> 
> ---
> base-commit: 8e5ab3f54a1061c2be3e1fbcda01fbe604c3450e
> change-id: 20231002-dma_iommu_fix-0a5397992f15
> 
> Best regards,