RE: [Resend] [PATCH] pci-hyperv: use kmalloc to allocate hypercall params buffer

[Long Li]

> -----Original Message-----
> From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx]
> Sent: Monday, November 7, 2016 11:00 PM
> To: Long Li <longli@xxxxxxxxxxxxx>
> Cc: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>;
> devel@xxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-
> pci@xxxxxxxxxxxxxxx
> Subject: Re: [Resend] [PATCH] pci-hyperv: use kmalloc to allocate hypercall
> params buffer
> 
> On Tue, Nov 08, 2016 at 12:14:14AM -0800, Long Li wrote:
> > From: Long Li <longli@xxxxxxxxxxxxx>
> >
> > hv_do_hypercall assumes that we pass a segment from a physically
> continuous buffer. Buffer allocated on the stack may not work if
> CONFIG_VMAP_STACK=y is set. Use kmalloc to allocate this buffer.
> 
> Please wrap your changelog at 72 columns.
> 
> >
> > Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> > Reported-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > ---
> >  drivers/pci/host/pci-hyperv.c | 24 +++++++++++++-----------
> >  1 file changed, 13 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/pci/host/pci-hyperv.c
> > b/drivers/pci/host/pci-hyperv.c index 763ff87..97e6daf 100644
> > --- a/drivers/pci/host/pci-hyperv.c
> > +++ b/drivers/pci/host/pci-hyperv.c
> > @@ -378,6 +378,7 @@ struct hv_pcibus_device {
> >  	struct msi_domain_info msi_info;
> >  	struct msi_controller msi_chip;
> >  	struct irq_domain *irq_domain;
> > +	struct retarget_msi_interrupt retarget_msi_interrupt_params;
> 
> Can you handle potentially unaligned accesses like this?  Is there some lock
> preventing you from using this structure more than once at the same time?
> 
> >  };
> >
> >  /*
> > @@ -774,7 +775,7 @@ 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 retarget_msi_interrupt *params;
> >  	struct hv_pcibus_device *hbus;
> >  	struct cpumask *dest;
> >  	struct pci_bus *pbus;
> > @@ -785,23 +786,24 @@ void hv_irq_unmask(struct irq_data *data)
> >  	pdev = msi_desc_to_pci_dev(msi_desc);
> >  	pbus = pdev->bus;
> >  	hbus = container_of(pbus->sysdata, struct hv_pcibus_device,
> > sysdata);
> > -
> > -	memset(&params, 0, sizeof(params));
> > -	params.partition_id = HV_PARTITION_ID_SELF;
> > -	params.source = 1; /* MSI(-X) */
> > -	params.address = msi_desc->msg.address_lo;
> > -	params.data = msi_desc->msg.data;
> > -	params.device_id = (hbus->hdev->dev_instance.b[5] << 24) |
> > +	params = &hbus->retarget_msi_interrupt_params;
> > +
> > +	memset(params, 0, sizeof(*params));
> > +	params->partition_id = HV_PARTITION_ID_SELF;
> > +	params->source = 1; /* MSI(-X) */
> > +	params->address = msi_desc->msg.address_lo;
> > +	params->data = msi_desc->msg.data;
> > +	params->device_id = (hbus->hdev->dev_instance.b[5] << 24) |
> >  			   (hbus->hdev->dev_instance.b[4] << 16) |
> >  			   (hbus->hdev->dev_instance.b[7] << 8) |
> >  			   (hbus->hdev->dev_instance.b[6] & 0xf8) |
> >  			   PCI_FUNC(pdev->devfn);
> > -	params.vector = cfg->vector;
> > +	params->vector = cfg->vector;
> >
> >  	for_each_cpu_and(cpu, dest, cpu_online_mask)
> > -		params.vp_mask |= (1ULL <<
> vmbus_cpu_number_to_vp_number(cpu));
> > +		params->vp_mask |= (1ULL <<
> vmbus_cpu_number_to_vp_number(cpu));
> >
> > -	hv_do_hypercall(HVCALL_RETARGET_INTERRUPT, &params, NULL);
> > +	hv_do_hypercall(HVCALL_RETARGET_INTERRUPT, params, NULL);
> 
> As you only use this in one spot, why not just allocate it here and then free
> it?  Why add it to the pcibus device structure?

Thanks Greg. I will send a V2.

> 
> thanks,
> 
> greg k-h