Re: [patch V4 08/14] PCI/MSI: Switch msi_capability_init() to guard(msi_desc_lock)

Bjorn Helgaas
2025-03-19T17:09:21Z

On Wed, Mar 19, 2025 at 11:56:53AM +0100, Thomas Gleixner wrote:
> Split the lock protected functionality of msi_capability_init() out into a
> helper function and use guard(msi_desc_lock) to replace the lock/unlock
> pair.
>
> No functional change intended.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
> V4: Split out from the previous combo patch
> ---
> drivers/pci/msi/msi.c | 68 ++++++++++++++++++++++++++------------------------
> 1 file changed, 36 insertions(+), 32 deletions(-)
>
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -336,38 +336,13 @@ static int msi_verify_entries(struct pci
> return !entry ? 0 : -EIO;
> }
>
> -/**
> - * msi_capability_init - configure device's MSI capability structure
> - * @dev: pointer to the pci_dev data structure of MSI device function
> - * @nvec: number of interrupts to allocate
> - * @affd: description of automatic IRQ affinity assignments (may be %NULL)
> - *
> - * Setup the MSI capability structure of the device with the requested
> - * number of interrupts. A return value of zero indicates the successful
> - * setup of an entry with the new MSI IRQ. A negative return value indicates
> - * an error, and a positive return value indicates the number of interrupts
> - * which could have been allocated.
> - */
> -static int msi_capability_init(struct pci_dev *dev, int nvec,
> - struct irq_affinity *affd)
> +static int __msi_capability_init(struct pci_dev *dev, int nvec, struct irq_affinity_desc *masks)
> {
> + int ret = msi_setup_msi_desc(dev, nvec, masks);
> struct msi_desc *entry, desc;
> - int ret;
> -
> - /* Reject multi-MSI early on irq domain enabled architectures */
> - if (nvec > 1 && !pci_msi_domain_supports(dev, MSI_FLAG_MULTI_PCI_MSI, ALLOW_LEGACY))
> - return 1;
> -
> - /* Disable MSI during setup in the hardware to erase stale state */
> - pci_msi_set_enable(dev, 0);
>
> - struct irq_affinity_desc *masks __free(kfree) =
> - affd ? irq_create_affinity_masks(nvec, affd) : NULL;
> -
> - msi_lock_descs(&dev->dev);
> - ret = msi_setup_msi_desc(dev, nvec, masks);
> if (ret)
> - goto unlock;
> + return ret;
>
> /* All MSIs are unmasked by default; mask them all */
> entry = msi_first_desc(&dev->dev, MSI_DESC_ALL);
> @@ -395,16 +370,45 @@ static int msi_capability_init(struct pc
>
> pcibios_free_irq(dev);
> dev->irq = entry->irq;
> - goto unlock;
> -
> + return 0;
> err:
> pci_msi_unmask(&desc, msi_multi_mask(&desc));
> pci_free_msi_irqs(dev);
> -unlock:
> - msi_unlock_descs(&dev->dev);
> return ret;
> }
>
> +/**
> + * msi_capability_init - configure device's MSI capability structure
> + * @dev: pointer to the pci_dev data structure of MSI device function
> + * @nvec: number of interrupts to allocate
> + * @affd: description of automatic IRQ affinity assignments (may be %NULL)
> + *
> + * Setup the MSI capability structure of the device with the requested
> + * number of interrupts. A return value of zero indicates the successful
> + * setup of an entry with the new MSI IRQ. A negative return value indicates
> + * an error, and a positive return value indicates the number of interrupts
> + * which could have been allocated.
> + */
> +static int msi_capability_init(struct pci_dev *dev, int nvec,
> + struct irq_affinity *affd)
> +{
> + /* Reject multi-MSI early on irq domain enabled architectures */
> + if (nvec > 1 && !pci_msi_domain_supports(dev, MSI_FLAG_MULTI_PCI_MSI, ALLOW_LEGACY))
> + return 1;
> +
> + /*
> + * Disable MSI during setup in the hardware, but mark it enabled
> + * so that setup code can evaluate it.
> + */
> + pci_msi_set_enable(dev, 0);
> +
> + struct irq_affinity_desc *masks __free(kfree) =
> + affd ? irq_create_affinity_masks(nvec, affd) : NULL;
> +
> + guard(msi_descs_lock)(&dev->dev);
> + return __msi_capability_init(dev, nvec, masks);
> +}
> +
> int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
> struct irq_affinity *affd)
> {
>