This is a note to let you know that I've just added the patch titled
PCI: Add PCI_ERROR_RESPONSE and related definitions
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pci-add-pci_error_response-and-related-definitions.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit edc4730e046fd4ac54c0de217a200076797c7b9f
Author: Naveen Naidu <naveennaidu479@xxxxxxxxx>
Date: Thu Nov 18 19:33:11 2021 +0530
PCI: Add PCI_ERROR_RESPONSE and related definitions
[ Upstream commit 57bdeef4716689d9b0e3571034d65cf420f6efcd ]
A config or MMIO read from a PCI device that doesn't exist or doesn't
respond causes a PCI error. There's no real data to return to satisfy the
CPU read, so most hardware fabricates ~0 data.
Add a PCI_ERROR_RESPONSE definition for that and use it where appropriate
to make these checks consistent and easier to find.
Also add helper definitions PCI_SET_ERROR_RESPONSE() and
PCI_POSSIBLE_ERROR() to make the code more readable.
Suggested-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Link: https://lore.kernel.org/r/55563bf4dfc5d3fdc96695373c659d099bf175b1.1637243717.git.naveennaidu479@xxxxxxxxx
Signed-off-by: Naveen Naidu <naveennaidu479@xxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Reviewed-by: Pali Rohár <pali@xxxxxxxxxx>
Stable-dep-of: c625dabbf1c4 ("x86/amd_nb: Check for invalid SMN reads")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 2636990e0cccf..edb37a5050da8 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -123,6 +123,15 @@ enum pci_interrupt_pin {
/* The number of legacy PCI INTx interrupts */
#define PCI_NUM_INTX 4
+/*
+ * Reading from a device that doesn't respond typically returns ~0. A
+ * successful read from a device may also return ~0, so you need additional
+ * information to reliably identify errors.
+ */
+#define PCI_ERROR_RESPONSE (~0ULL)
+#define PCI_SET_ERROR_RESPONSE(val) (*(val) = ((typeof(*(val))) PCI_ERROR_RESPONSE))
+#define PCI_POSSIBLE_ERROR(val) ((val) == ((typeof(val)) PCI_ERROR_RESPONSE))
+
/*
* pci_power_t values must match the bits in the Capabilities PME_Support
* and Control/Status PowerState fields in the Power Management capability.
