Re: [PATCH v2 2/3] PCI: hv: Move retarget related structures into tlfs header

[Andrew Murray <amurray@thegoodpenguin.co.uk>]

On Mon, Feb 03, 2020 at 01:03:12PM +0800, Boqun Feng wrote:
> Currently, retarget_msi_interrupt and other structures it relys on are
> defined in pci-hyperv.c. However, those structures are actually defined
> in Hypervisor Top-Level Functional Specification [1] and may be
> different in sizes of fields or layout from architecture to
> architecture. Therefore, this patch moves those definitions into x86's

Nit: Rather than 'Therefore, this patch moves ...' - how about 'Let's move
...'?

> tlfs header file to support virtual PCI on non-x86 architectures in the
> future.
> 
> Besides, while I'm at it, rename retarget_msi_interrupt to

Nit: 'Besides, while I'm at it' - this type of wording describes what
*you've* done rather than what the patch is doing. You could replace
that quoted text with 'Additionally, '

> hv_retarget_msi_interrupt for the consistent name convention, also

Nit: s/name/naming

> mirroring the name in TLFS.
> 
> [1]: https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/reference/tlfs
> 
> Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@gmail.com>
> ---
>  arch/x86/include/asm/hyperv-tlfs.h  | 31 ++++++++++++++++++++++++++
>  drivers/pci/controller/pci-hyperv.c | 34 ++---------------------------
>  2 files changed, 33 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 739bd89226a5..4a76e442481a 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -911,4 +911,35 @@ struct hv_tlb_flush_ex {
>  struct hv_partition_assist_pg {
>  	u32 tlb_lock_count;
>  };
> +
> +struct hv_interrupt_entry {
> +	u32 source;			/* 1 for MSI(-X) */
> +	u32 reserved1;
> +	u32 address;
> +	u32 data;
> +} __packed;

Why have you added __packed here? There is no mention of this change in the
commit log? Is it needed?

> +
> +/*
> + * flags for hv_device_interrupt_target.flags
> + */
> +#define HV_DEVICE_INTERRUPT_TARGET_MULTICAST		1
> +#define HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET	2
> +
> +struct hv_device_interrupt_target {
> +	u32 vector;
> +	u32 flags;
> +	union {
> +		u64 vp_mask;
> +		struct hv_vpset vp_set;
> +	};
> +} __packed;

Same here.

> +
> +/* HvRetargetDeviceInterrupt hypercall */
> +struct hv_retarget_device_interrupt {
> +	u64 partition_id;

Why drop the 'self' comment?

> +	u64 device_id;
> +	struct hv_interrupt_entry int_entry;
> +	u64 reserved2;
> +	struct hv_device_interrupt_target int_target;
> +} __packed __aligned(8);
>  #endif
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index aacfcc90d929..0d9b74503577 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -406,36 +406,6 @@ struct pci_eject_response {
>  
>  static int pci_ring_size = (4 * PAGE_SIZE);
>  
> -struct hv_interrupt_entry {
> -	u32	source;			/* 1 for MSI(-X) */
> -	u32	reserved1;
> -	u32	address;
> -	u32	data;
> -};
> -
> -/*
> - * flags for hv_device_interrupt_target.flags
> - */
> -#define HV_DEVICE_INTERRUPT_TARGET_MULTICAST		1
> -#define HV_DEVICE_INTERRUPT_TARGET_PROCESSOR_SET	2
> -
> -struct hv_device_interrupt_target {
> -	u32	vector;
> -	u32	flags;
> -	union {
> -		u64		 vp_mask;
> -		struct hv_vpset vp_set;
> -	};
> -};
> -
> -struct retarget_msi_interrupt {
> -	u64	partition_id;		/* use "self" */
> -	u64	device_id;
> -	struct hv_interrupt_entry int_entry;
> -	u64	reserved2;
> -	struct hv_device_interrupt_target int_target;
> -} __packed __aligned(8);
> -
>  /*
>   * Driver specific state.
>   */
> @@ -482,7 +452,7 @@ struct hv_pcibus_device {
>  	struct workqueue_struct *wq;
>  
>  	/* hypercall arg, must not cross page boundary */
> -	struct retarget_msi_interrupt retarget_msi_interrupt_params;
> +	struct hv_retarget_device_interrupt retarget_msi_interrupt_params;
>  
>  	/*
>  	 * Don't put anything here: retarget_msi_interrupt_params must be last
> @@ -1178,7 +1148,7 @@ static void hv_irq_unmask(struct irq_data *data)
>  {
>  	struct msi_desc *msi_desc = irq_data_get_msi_desc(data);
>  	struct irq_cfg *cfg = irqd_cfg(data);
> -	struct retarget_msi_interrupt *params;
> +	struct hv_retarget_device_interrupt *params;

pci-hyperv.c also makes use of retarget_msi_interrupt_lock - it's really clear
from this name what it protects, however your rename now makes this more
confusing.

Likewise there is a comment in hv_pci_probe that refers to
retarget_msi_interrupt_params which is now stale.

It may be helpful to rename hv_retarget_device_interrupt for consistency with
the docs - however please make sure you catch all the references - I'd suggest
that the move and the rename are in different patches.

Thanks,

Andrew Murray

>  	struct hv_pcibus_device *hbus;
>  	struct cpumask *dest;
>  	cpumask_var_t tmp;
> -- 
> 2.24.1
>