From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Nothing enforces the posted writes to be visible when the function
returns. Flush them even if the flush might be redundant when the entry is
masked already as the unmask will flush as well. This is either setup or a
rare affinity change event so the extra flush is not the end of the world.
While this is more a theoretical issue especially the logic in the X86
specific msi_set_affinity() function relies on the assumption that the
update has reached the hardware when the function returns.
Again, as this never has been enforced the Fixes tag refers to a commit in:
git://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Fixes: f036d4ea5fa7 ("[PATCH] ia32 Message Signalled Interrupt support")
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx>
Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
drivers/pci/msi.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -311,6 +311,9 @@ void __pci_write_msi_msg(struct msi_desc
if (unmasked)
__pci_msix_desc_mask_irq(entry, 0);
+
+ /* Ensure that the writes are visible in the device */
+ readl(base + PCI_MSIX_ENTRY_DATA);
} else {
int pos = dev->msi_cap;
u16 msgctl;
@@ -331,6 +334,8 @@ void __pci_write_msi_msg(struct msi_desc
pci_write_config_word(dev, pos + PCI_MSI_DATA_32,
msg->data);
}
+ /* Ensure that the writes are visible in the device */
+ pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &msgctl);
}
skip:
