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@google.com>
Link: https://lore.kernel.org/r/55563bf4dfc5d3fdc96695373c659d099bf175b1.1637243717.git.naveennaidu479@gmail.com
Signed-off-by: Naveen Naidu <naveennaidu479@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pali Rohár <pali@kernel.org>
Stable-dep-of: c625dabbf1c4 ("x86/amd_nb: Check for invalid SMN reads")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 1cd5caa567cf57b9cb679d63ceea2741d6da2d52..7edc6de9e88c29fb630e1a834d94e70024cbb9fc 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -129,6 +129,15 @@ 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.