Commit 2c269f42 authored by Marek Marczykowski-Górecki's avatar Marek Marczykowski-Górecki Committed by Juergen Gross
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xen-pciback: Consider INTx disabled when MSI/MSI-X is enabled 



Linux enables MSI-X before disabling INTx, but keeps MSI-X masked until
the table is filled. Then it disables INTx just before clearing MASKALL
bit. Currently this approach is rejected by xen-pciback.
According to the PCIe spec, device cannot use INTx when MSI/MSI-X is
enabled (in other words: enabling MSI/MSI-X implicitly disables INTx).

Change the logic to consider INTx disabled if MSI/MSI-X is enabled. This
applies to three places:
 - checking currently enabled interrupts type,
 - transition to MSI/MSI-X - where INTx would be implicitly disabled,
 - clearing INTx disable bit - which can be allowed even if MSI/MSI-X is
   enabled, as device should consider INTx disabled anyway in that case

Fixes: 5e29500e ("xen-pciback: Allow setting PCI_MSIX_FLAGS_MASKALL too")
Signed-off-by: default avatarMarek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: default avatarJuergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20231016131348.1734721-1-marmarek@invisiblethingslab.com


Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent f0d7db7b

drivers/xen/xen-pciback/conf_space.c

+13 −6
Original line number Diff line number Diff line
@@ -288,12 +288,6 @@ int xen_pcibk_get_interrupt_type(struct pci_dev *dev) 
	u16 val;

	int ret = 0;



	err = pci_read_config_word(dev, PCI_COMMAND, &val);

	if (err)

		return err;

	if (!(val & PCI_COMMAND_INTX_DISABLE))

		ret |= INTERRUPT_TYPE_INTX;



	/*

	 * Do not trust dev->msi(x)_enabled here, as enabling could be done

	 * bypassing the pci_*msi* functions, by the qemu.
@@ -316,6 +310,19 @@ int xen_pcibk_get_interrupt_type(struct pci_dev *dev) 
		if (val & PCI_MSIX_FLAGS_ENABLE)

			ret |= INTERRUPT_TYPE_MSIX;

	}



	/*

	 * PCIe spec says device cannot use INTx if MSI/MSI-X is enabled,

	 * so check for INTx only when both are disabled.

	 */

	if (!ret) {

		err = pci_read_config_word(dev, PCI_COMMAND, &val);

		if (err)

			return err;

		if (!(val & PCI_COMMAND_INTX_DISABLE))

			ret |= INTERRUPT_TYPE_INTX;

	}



	return ret ?: INTERRUPT_TYPE_NONE;

}

drivers/xen/xen-pciback/conf_space_capability.c

+7 −1
Original line number Diff line number Diff line
@@ -236,10 +236,16 @@ static int msi_msix_flags_write(struct pci_dev *dev, int offset, u16 new_value, 
		return PCIBIOS_SET_FAILED;



	if (new_value & field_config->enable_bit) {

		/* don't allow enabling together with other interrupt types */

		/*

		 * Don't allow enabling together with other interrupt type, but do

		 * allow enabling MSI(-X) while INTx is still active to please Linuxes

		 * MSI(-X) startup sequence. It is safe to do, as according to PCI

		 * spec, device with enabled MSI(-X) shouldn't use INTx.

		 */

		int int_type = xen_pcibk_get_interrupt_type(dev);



		if (int_type == INTERRUPT_TYPE_NONE ||

		    int_type == INTERRUPT_TYPE_INTX ||

		    int_type == field_config->int_type)

			goto write;

		return PCIBIOS_SET_FAILED;

drivers/xen/xen-pciback/conf_space_header.c

+3 −18
Original line number Diff line number Diff line
@@ -104,24 +104,9 @@ static int command_write(struct pci_dev *dev, int offset, u16 value, void *data) 
		pci_clear_mwi(dev);

	}



	if (dev_data && dev_data->allow_interrupt_control) {

		if ((cmd->val ^ value) & PCI_COMMAND_INTX_DISABLE) {

			if (value & PCI_COMMAND_INTX_DISABLE) {

				pci_intx(dev, 0);

			} else {

				/* Do not allow enabling INTx together with MSI or MSI-X. */

				switch (xen_pcibk_get_interrupt_type(dev)) {

				case INTERRUPT_TYPE_NONE:

					pci_intx(dev, 1);

					break;

				case INTERRUPT_TYPE_INTX:

					break;

				default:

					return PCIBIOS_SET_FAILED;

				}

			}

		}

	}

	if (dev_data && dev_data->allow_interrupt_control &&

	    ((cmd->val ^ value) & PCI_COMMAND_INTX_DISABLE))

		pci_intx(dev, !(value & PCI_COMMAND_INTX_DISABLE));



	cmd->val = value;