Re: [patch V2 07/31] PCI/MSI: Protect MSI operations

[Bjorn Helgaas <helgaas@xxxxxxxxxx>]

On Mon, Dec 06, 2021 at 11:51:13PM +0100, Thomas Gleixner wrote:
> To prepare for dynamic extension of MSI-X vectors, protect the MSI
> operations for MSI and MSI-X. This requires to move the invocation of
> irq_create_affinity_masks() out of the descriptor lock section to avoid
> reverse lock ordering vs. CPU hotplug lock as some callers of the PCI/MSI
> allocation interfaces already hold it.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

> ---
>  drivers/pci/msi/irqdomain.c |    4 -
>  drivers/pci/msi/msi.c       |  120 
> ++++++++++++++++++++++++++------------------
>  2 files changed, 73 insertions(+), 51 deletions(-)
> 
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -14,7 +14,7 @@ int pci_msi_setup_msi_irqs(struct pci_de
>  
>       domain = dev_get_msi_domain(&dev->dev);
>       if (domain && irq_domain_is_hierarchy(domain))
> -             return msi_domain_alloc_irqs(domain, &dev->dev, nvec);
> +             return msi_domain_alloc_irqs_descs_locked(domain, &dev->dev, 
> nvec);
>  
>       return pci_msi_legacy_setup_msi_irqs(dev, nvec, type);
>  }
> @@ -25,7 +25,7 @@ void pci_msi_teardown_msi_irqs(struct pc
>  
>       domain = dev_get_msi_domain(&dev->dev);
>       if (domain && irq_domain_is_hierarchy(domain))
> -             msi_domain_free_irqs(domain, &dev->dev);
> +             msi_domain_free_irqs_descs_locked(domain, &dev->dev);
>       else
>               pci_msi_legacy_teardown_msi_irqs(dev);
>  }
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -322,11 +322,13 @@ static void __pci_restore_msix_state(str
>  
>       write_msg = arch_restore_msi_irqs(dev);
>  
> +     msi_lock_descs(&dev->dev);
>       for_each_pci_msi_entry(entry, dev) {
>               if (write_msg)
>                       __pci_write_msi_msg(entry, &entry->msg);
>               pci_msix_write_vector_ctrl(entry, entry->pci.msix_ctrl);
>       }
> +     msi_unlock_descs(&dev->dev);
>  
>       pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
>  }
> @@ -339,20 +341,16 @@ void pci_restore_msi_state(struct pci_de
>  EXPORT_SYMBOL_GPL(pci_restore_msi_state);
>  
>  static struct msi_desc *
> -msi_setup_entry(struct pci_dev *dev, int nvec, struct irq_affinity *affd)
> +msi_setup_entry(struct pci_dev *dev, int nvec, struct irq_affinity_desc 
> *masks)
>  {
> -     struct irq_affinity_desc *masks = NULL;
>       struct msi_desc *entry;
>       unsigned long prop;
>       u16 control;
>  
> -     if (affd)
> -             masks = irq_create_affinity_masks(nvec, affd);
> -
>       /* MSI Entry Initialization */
>       entry = alloc_msi_entry(&dev->dev, nvec, masks);
>       if (!entry)
> -             goto out;
> +             return NULL;
>  
>       pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
>       /* Lies, damned lies, and MSIs */
> @@ -379,8 +377,7 @@ msi_setup_entry(struct pci_dev *dev, int
>       if (entry->pci.msi_attrib.is_64)
>               prop |= MSI_PROP_64BIT;
>       msi_device_set_properties(&dev->dev, prop);
> -out:
> -     kfree(masks);
> +
>       return entry;
>  }
>  
> @@ -416,14 +413,21 @@ static int msi_verify_entries(struct pci
>  static int msi_capability_init(struct pci_dev *dev, int nvec,
>                              struct irq_affinity *affd)
>  {
> +     struct irq_affinity_desc *masks = NULL;
>       struct msi_desc *entry;
>       int ret;
>  
>       pci_msi_set_enable(dev, 0);     /* Disable MSI during set up */
>  
> -     entry = msi_setup_entry(dev, nvec, affd);
> -     if (!entry)
> -             return -ENOMEM;
> +     if (affd)
> +             masks = irq_create_affinity_masks(nvec, affd);
> +
> +     msi_lock_descs(&dev->dev);
> +     entry = msi_setup_entry(dev, nvec, masks);
> +     if (!entry) {
> +             ret = -ENOMEM;
> +             goto unlock;
> +     }
>  
>       /* All MSIs are unmasked by default; mask them all */
>       pci_msi_mask(entry, msi_multi_mask(entry));
> @@ -446,11 +450,14 @@ static int msi_capability_init(struct pc
>  
>       pcibios_free_irq(dev);
>       dev->irq = entry->irq;
> -     return 0;
> +     goto unlock;
>  
>  err:
>       pci_msi_unmask(entry, msi_multi_mask(entry));
>       free_msi_irqs(dev);
> +unlock:
> +     msi_unlock_descs(&dev->dev);
> +     kfree(masks);
>       return ret;
>  }
>  
> @@ -477,23 +484,18 @@ static void __iomem *msix_map_region(str
>  
>  static int msix_setup_entries(struct pci_dev *dev, void __iomem *base,
>                             struct msix_entry *entries, int nvec,
> -                           struct irq_affinity *affd)
> +                           struct irq_affinity_desc *masks)
>  {
> -     struct irq_affinity_desc *curmsk, *masks = NULL;
> +     int i, vec_count = pci_msix_vec_count(dev);
> +     struct irq_affinity_desc *curmsk;
>       struct msi_desc *entry;
>       void __iomem *addr;
> -     int ret, i;
> -     int vec_count = pci_msix_vec_count(dev);
> -
> -     if (affd)
> -             masks = irq_create_affinity_masks(nvec, affd);
>  
>       for (i = 0, curmsk = masks; i < nvec; i++) {
>               entry = alloc_msi_entry(&dev->dev, 1, curmsk);
>               if (!entry) {
>                       /* No enough memory. Don't try again */
> -                     ret = -ENOMEM;
> -                     goto out;
> +                     return -ENOMEM;
>               }
>  
>               entry->pci.msi_attrib.is_msix   = 1;
> @@ -522,10 +524,7 @@ static int msix_setup_entries(struct pci
>                       curmsk++;
>       }
>       msi_device_set_properties(&dev->dev, MSI_PROP_PCI_MSIX | 
> MSI_PROP_64BIT);
> -     ret = 0;
> -out:
> -     kfree(masks);
> -     return ret;
> +     return 0;
>  }
>  
>  static void msix_update_entries(struct pci_dev *dev, struct msix_entry 
> *entries)
> @@ -552,6 +551,41 @@ static void msix_mask_all(void __iomem *
>               writel(ctrl, base + PCI_MSIX_ENTRY_VECTOR_CTRL);
>  }
>  
> +static int msix_setup_interrupts(struct pci_dev *dev, void __iomem *base,
> +                              struct msix_entry *entries, int nvec,
> +                              struct irq_affinity *affd)
> +{
> +     struct irq_affinity_desc *masks = NULL;
> +     int ret;
> +
> +     if (affd)
> +             masks = irq_create_affinity_masks(nvec, affd);
> +
> +     msi_lock_descs(&dev->dev);
> +     ret = msix_setup_entries(dev, base, entries, nvec, masks);
> +     if (ret)
> +             goto out_free;
> +
> +     ret = pci_msi_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
> +     if (ret)
> +             goto out_free;
> +
> +     /* Check if all MSI entries honor device restrictions */
> +     ret = msi_verify_entries(dev);
> +     if (ret)
> +             goto out_free;
> +
> +     msix_update_entries(dev, entries);
> +     goto out_unlock;
> +
> +out_free:
> +     free_msi_irqs(dev);
> +out_unlock:
> +     msi_unlock_descs(&dev->dev);
> +     kfree(masks);
> +     return ret;
> +}
> +
>  /**
>   * msix_capability_init - configure device's MSI-X capability
>   * @dev: pointer to the pci_dev data structure of MSI-X device function
> @@ -592,20 +626,9 @@ static int msix_capability_init(struct p
>       /* Ensure that all table entries are masked. */
>       msix_mask_all(base, tsize);
>  
> -     ret = msix_setup_entries(dev, base, entries, nvec, affd);
> +     ret = msix_setup_interrupts(dev, base, entries, nvec, affd);
>       if (ret)
> -             goto out_free;
> -
> -     ret = pci_msi_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
> -     if (ret)
> -             goto out_free;
> -
> -     /* Check if all MSI entries honor device restrictions */
> -     ret = msi_verify_entries(dev);
> -     if (ret)
> -             goto out_free;
> -
> -     msix_update_entries(dev, entries);
> +             goto out_disable;
>  
>       /* Set MSI-X enabled bits and unmask the function */
>       pci_intx_for_msi(dev, 0);
> @@ -615,12 +638,8 @@ static int msix_capability_init(struct p
>       pcibios_free_irq(dev);
>       return 0;
>  
> -out_free:
> -     free_msi_irqs(dev);
> -
>  out_disable:
>       pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
> -
>       return ret;
>  }
>  
> @@ -725,8 +744,10 @@ void pci_disable_msi(struct pci_dev *dev
>       if (!pci_msi_enable || !dev || !dev->msi_enabled)
>               return;
>  
> +     msi_lock_descs(&dev->dev);
>       pci_msi_shutdown(dev);
>       free_msi_irqs(dev);
> +     msi_unlock_descs(&dev->dev);
>  }
>  EXPORT_SYMBOL(pci_disable_msi);
>  
> @@ -812,8 +833,10 @@ void pci_disable_msix(struct pci_dev *de
>       if (!pci_msi_enable || !dev || !dev->msix_enabled)
>               return;
>  
> +     msi_lock_descs(&dev->dev);
>       pci_msix_shutdown(dev);
>       free_msi_irqs(dev);
> +     msi_unlock_descs(&dev->dev);
>  }
>  EXPORT_SYMBOL(pci_disable_msix);
>  
> @@ -874,7 +897,6 @@ int pci_enable_msi(struct pci_dev *dev)
>  
>       if (!rc)
>               rc = __pci_enable_msi_range(dev, 1, 1, NULL);
> -
>       return rc < 0 ? rc : 0;
>  }
>  EXPORT_SYMBOL(pci_enable_msi);
> @@ -961,11 +983,7 @@ int pci_alloc_irq_vectors_affinity(struc
>                                  struct irq_affinity *affd)
>  {
>       struct irq_affinity msi_default_affd = {0};
> -     int ret = msi_setup_device_data(&dev->dev);
> -     int nvecs = -ENOSPC;
> -
> -     if (ret)
> -             return ret;
> +     int ret, nvecs;
>  
>       if (flags & PCI_IRQ_AFFINITY) {
>               if (!affd)
> @@ -975,6 +993,10 @@ int pci_alloc_irq_vectors_affinity(struc
>                       affd = NULL;
>       }
>  
> +     ret = msi_setup_device_data(&dev->dev);
> +     if (ret)
> +             return ret;
> +
>       if (flags & PCI_IRQ_MSIX) {
>               nvecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,
>                                               affd, flags);
> @@ -1003,7 +1025,7 @@ int pci_alloc_irq_vectors_affinity(struc
>               }
>       }
>  
> -     return nvecs;
> +     return -ENOSPC;
>  }
>  EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);
>  
>