linux-kernel - Re: [RFC 1/4] s390/pci: track alignment/length strictness for zpci

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Date:   Thu, 10 Dec 2020 11:33:18 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>
Cc:     alex.williamson@...hat.com, schnelle@...ux.ibm.com,
        pmorel@...ux.ibm.com, borntraeger@...ibm.com, hca@...ux.ibm.com,
        gor@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/4] s390/pci: track alignment/length strictness for
 zpci_dev

On Wed,  9 Dec 2020 15:27:47 -0500
Matthew Rosato <mjrosato@...ux.ibm.com> wrote:

> Some zpci device types (e.g., ISM) follow different rules for length
> and alignment of pci instructions.  Recognize this and keep track of
> it in the zpci_dev.
> 
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> Reviewed-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> Reviewed-by: Pierre Morel <pmorel@...ux.ibm.com>
> ---
>  arch/s390/include/asm/pci.h     | 3 ++-
>  arch/s390/include/asm/pci_clp.h | 4 +++-
>  arch/s390/pci/pci_clp.c         | 1 +
>  3 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 2126289..f16ffba 100644
> --- a/arch/s390/include/asm/pci.h
> +++ b/arch/s390/include/asm/pci.h
> @@ -133,7 +133,8 @@ struct zpci_dev {
>  	u8		has_hp_slot	: 1;
>  	u8		is_physfn	: 1;
>  	u8		util_str_avail	: 1;
> -	u8		reserved	: 4;
> +	u8		relaxed_align	: 1;
> +	u8		reserved	: 3;
>  	unsigned int	devfn;		/* DEVFN part of the RID*/
>  
>  	struct mutex lock;
> diff --git a/arch/s390/include/asm/pci_clp.h b/arch/s390/include/asm/pci_clp.h
> index 1f4b666..9fb7cbf 100644
> --- a/arch/s390/include/asm/pci_clp.h
> +++ b/arch/s390/include/asm/pci_clp.h
> @@ -150,7 +150,9 @@ struct clp_rsp_query_pci_grp {
>  	u16			:  4;
>  	u16 noi			: 12;	/* number of interrupts */
>  	u8 version;
> -	u8			:  6;
> +	u8			:  4;
> +	u8 relaxed_align	:  1;	/* Relax length and alignment rules */
> +	u8			:  1;
>  	u8 frame		:  1;
>  	u8 refresh		:  1;	/* TLB refresh mode */
>  	u16 reserved2;
> diff --git a/arch/s390/pci/pci_clp.c b/arch/s390/pci/pci_clp.c
> index 153720d..630f8fc 100644
> --- a/arch/s390/pci/pci_clp.c
> +++ b/arch/s390/pci/pci_clp.c
> @@ -103,6 +103,7 @@ static void clp_store_query_pci_fngrp(struct zpci_dev *zdev,
>  	zdev->max_msi = response->noi;
>  	zdev->fmb_update = response->mui;
>  	zdev->version = response->version;
> +	zdev->relaxed_align = response->relaxed_align;
>  
>  	switch (response->version) {
>  	case 1:

Hm, what does that 'relaxed alignment' imply? Is that something that
can apply to emulated devices as well?