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: 5e29500eba2a ("xen-pciback: Allow setting PCI_MSIX_FLAGS_MASKALL too")
Signed-off-by: Marek Marczykowski-Górecki <[email protected]>
Acked-by: Juergen Gross <[email protected]>
---
Changes in v4:
- update comment (retain A-b)
Changes in v3:
- allow clearing INTx regardless of MSI/MSI-X state, to be consistent
with enabling MSI/MSI-X
Changes in v2:
- restructure the patch to consider not only MASKALL bit, but enabling
MSI/MSI-X generally, without explicitly disabling INTx first
---
drivers/xen/xen-pciback/conf_space.c | 19 +++++++++++------
.../xen/xen-pciback/conf_space_capability.c | 8 ++++++-
drivers/xen/xen-pciback/conf_space_header.c | 21 +++----------------
3 files changed, 23 insertions(+), 25 deletions(-)
diff --git a/drivers/xen/xen-pciback/conf_space.c b/drivers/xen/xen-pciback/conf_space.c
index 059de92aea7d..d47eee6c5143 100644
--- a/drivers/xen/xen-pciback/conf_space.c
+++ b/drivers/xen/xen-pciback/conf_space.c
@@ -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;
}
diff --git a/drivers/xen/xen-pciback/conf_space_capability.c b/drivers/xen/xen-pciback/conf_space_capability.c
index 097316a74126..1948a9700c8f 100644
--- a/drivers/xen/xen-pciback/conf_space_capability.c
+++ b/drivers/xen/xen-pciback/conf_space_capability.c
@@ -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;
diff --git a/drivers/xen/xen-pciback/conf_space_header.c b/drivers/xen/xen-pciback/conf_space_header.c
index 981435103af1..fc0332645966 100644
--- a/drivers/xen/xen-pciback/conf_space_header.c
+++ b/drivers/xen/xen-pciback/conf_space_header.c
@@ -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;
--
2.41.0