linux-kernel - Re: [PATCH 12/32] s390/pci: get SHM information from list pci

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Date:   Wed, 08 Dec 2021 13:21:35 +0100
From:   Niklas Schnelle <schnelle@...ux.ibm.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>, linux-s390@...r.kernel.org
Cc:     alex.williamson@...hat.com, cohuck@...hat.com,
        farman@...ux.ibm.com, pmorel@...ux.ibm.com,
        borntraeger@...ux.ibm.com, hca@...ux.ibm.com, gor@...ux.ibm.com,
        gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
        frankja@...ux.ibm.com, david@...hat.com, imbrenda@...ux.ibm.com,
        vneethv@...ux.ibm.com, oberpar@...ux.ibm.com, freude@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/32] s390/pci: get SHM information from list pci

On Tue, 2021-12-07 at 15:57 -0500, Matthew Rosato wrote:
> KVM will need information on the special handle mask used to indicate
> emulated devices.  In order to obtain this, a new type of list pci call
> must be made to gather the information.  Remove the unused data pointer
> from clp_list_pci and __clp_add and instead optionally pass a pointer to
> a model-dependent-data field.  Additionally, allow for clp_list_pci calls
> that don't specify a callback - in this case, just do the first pass of
> list pci and exit.
> 
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
> ---
>  arch/s390/include/asm/pci.h     |  6 ++++++
>  arch/s390/include/asm/pci_clp.h |  2 +-
>  arch/s390/pci/pci.c             | 19 +++++++++++++++++++
>  arch/s390/pci/pci_clp.c         | 16 ++++++++++------
>  4 files changed, 36 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 00a2c24d6d2b..86f43644756d 100644
> --- a/arch/s390/include/asm/pci.h
> +++ b/arch/s390/include/asm/pci.h
> @@ -219,12 +219,18 @@ int zpci_unregister_ioat(struct zpci_dev *, u8);
>  void zpci_remove_reserved_devices(void);
>  void zpci_update_fh(struct zpci_dev *zdev, u32 fh);
> 
---8<---
> -static int clp_list_pci(struct clp_req_rsp_list_pci *rrb, void *data,
> -			void (*cb)(struct clp_fh_list_entry *, void *))
> +int clp_list_pci(struct clp_req_rsp_list_pci *rrb, u32 *mdd,
> +		 void (*cb)(struct clp_fh_list_entry *))
>  {
>  	u64 resume_token = 0;
>  	int nentries, i, rc;
> @@ -368,8 +368,12 @@ static int clp_list_pci(struct clp_req_rsp_list_pci *rrb, void *data,
>  		rc = clp_list_pci_req(rrb, &resume_token, &nentries);
>  		if (rc)
>  			return rc;
> +		if (mdd)
> +			*mdd = rrb->response.mdd;
> +		if (!cb)
> +			return 0;

I think it would be slightly cleaner to instead de-static
clp_list_pci_req() and call that directly. Just because that makes the
clp_list_pci() still list all PCI functions and allows us to get rid of
the data parameter completely.

Also, I've been thinking about moving clp_scan_devices(),
clp_get_state(), and clp_refresh_fh() out of pci_clp.c because they are
higher level. I think that would nicely fit your zpci_get_mdd() in
pci.c with or without the above suggestion. Then we could do the
removal of the unused data parameter in that series as a cleanup. What
do you think?

>  		for (i = 0; i < nentries; i++)
> -			cb(&rrb->response.fh_list[i], data);
> +			cb(&rrb->response.fh_list[i]);
>  	} while (resume_token);
>  
>  	return rc;
> @@ -398,7 +402,7 @@ static int clp_find_pci(struct clp_req_rsp_list_pci *rrb, u32 fid,
>  	return -ENODEV;
>  }
>  
> -static void __clp_add(struct clp_fh_list_entry *entry, void *data)
> +static void __clp_add(struct clp_fh_list_entry *entry)
>  {
>  	struct zpci_dev *zdev;
>