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

Bjorn Helgaas
2021-12-07T21:07:03Z

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@linutronix.de>

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

> ---
> 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);
>
>