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

From: Greg KH
Date: Tue Nov 08 2016 - 02:00:01 EST


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 k-h