Patch "PCI: Add PCI_ERROR_RESPONSE and related definitions" has been added to the 5.4-stable tree

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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 5.4-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-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f23bee71411244d539230f541d2dbb609cfea5c3
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 1cd5caa567cf5..7edc6de9e88c2 100644
--- 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.




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