linux-kernel - Re: [PATCH 3.16 098/217] s390/pci: enforce fmb page boundary rule

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Date:	Wed, 27 Apr 2016 19:27:35 +0200 (CEST)
From:	Sebastian Ott <sebott@...ux.vnet.ibm.com>
To:	Ben Hutchings <ben@...adent.org.uk>
cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	akpm@...ux-foundation.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 3.16 098/217] s390/pci: enforce fmb page boundary rule

On Wed, 27 Apr 2016, Ben Hutchings wrote:
> 3.16.35-rc1 review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Sebastian Ott <sebott@...ux.vnet.ibm.com>
> 
> commit 80c544ded25ac14d7cc3e555abb8ed2c2da99b84 upstream.
> 
> The function measurement block must not cross a page boundary. Ensure
> that by raising the alignment requirement to the smallest power of 2
> larger than the size of the fmb.
> 
> Fixes: d0b088531 ("s390/pci: performance statistics and debug infrastructure")
> Signed-off-by: Sebastian Ott <sebott@...ux.vnet.ibm.com>
> Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
> [bwh: Backported to 3.16: adjust context]
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>

The BUILD_BUG_ON below will be triggered. This patch has a
dependency on commit:
	6001018ae "s390/pci: extract software counters from fmb"
could you please fetch that one too?

Thanks,
Sebastian

> ---
>  arch/s390/include/asm/pci.h | 2 +-
>  arch/s390/pci/pci.c         | 5 ++++-
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> --- a/arch/s390/include/asm/pci.h
> +++ b/arch/s390/include/asm/pci.h
> @@ -48,7 +48,7 @@ struct zpci_fmb {
>  	atomic64_t allocated_pages;
>  	atomic64_t mapped_pages;
>  	atomic64_t unmapped_pages;
> -} __packed __aligned(16);
> +} __packed __aligned(64);
> 
>  #define ZPCI_MSI_VEC_BITS	11
>  #define ZPCI_MSI_VEC_MAX	(1 << ZPCI_MSI_VEC_BITS)
> --- a/arch/s390/pci/pci.c
> +++ b/arch/s390/pci/pci.c
> @@ -840,8 +840,11 @@ static inline int barsize(u8 size)
> 
>  static int zpci_mem_init(void)
>  {
> +	BUILD_BUG_ON(!is_power_of_2(__alignof__(struct zpci_fmb)) ||
> +		     __alignof__(struct zpci_fmb) < sizeof(struct zpci_fmb));
> +
>  	zdev_fmb_cache = kmem_cache_create("PCI_FMB_cache", sizeof(struct zpci_fmb),
> -				16, 0, NULL);
> +					   __alignof__(struct zpci_fmb), 0, NULL);
>  	if (!zdev_fmb_cache)
>  		goto error_zdev;
> 
> 
>