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

Boqun Feng
2020-02-03T14:09:13Z

On Mon, Feb 03, 2020 at 09:41:18AM +0000, Andrew Murray wrote:
> 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
>

Thanks for the suggestion on wording ;-)

> > 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?
>

I'm simply following the convention of hyperv-tlfs.h: most of the
structures have this "__packed" attribute. I personally don't think this
attribute is necessary, but I was afraid that I was missing something
subtle. So a question for folks working on Hyper-V: why we need this
attribute on TLFS-defined structures? Most of those will have no
difference with or without this attribute, IIUC.

> > +
> > +/*
> > + * 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?
>

Good catch, TLFS does say this field must be 'self'. I will add it in
next version.

> > + 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.
>

But 'retarget_msi_interrupt_params' is the name of field in
hv_pcibus_device, so is 'retarget_msi_interrupt_lock'. And what I change
is the name of type. I believe people can tell the relationship from
the name of the fields, and the comment of hv_pci_probe actually refers
to the field rather than the type.

> 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.
>

If the renaming requires a lot of work (e.g. need to change multiple
references), I will follow your suggestion. But seems it's not the case
for this renaming.

Regards,
Boqun

> Thanks,
>
> Andrew Murray
>
> > struct hv_pcibus_device *hbus;
> > struct cpumask *dest;
> > cpumask_var_t tmp;
> > --
> > 2.24.1
> >