[virtio-comment] [PATCH v7 3/5] pci: Define virtio_pci_cap64

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Define 'virtio_pci_cap64' to allow capabilities to describe
memory regions larger than, or with an offset larger than 4GiB.

This will be used by the shared memory region capability.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
---
 content.tex | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/content.tex b/content.tex
index fafa532..d481359 100644
--- a/content.tex
+++ b/content.tex
@@ -746,6 +746,23 @@ \subsection{Virtio Structure PCI Capabilities}\label{sec:Virtio Transport Option
         \end{note}
 \end{description}
 
+A variant of this type, struct virtio_pci_cap64, is defined for
+those capaibilites that require offsets or lengths larger than
+4GiB:
+
+\begin{lstlisting}
+struct virtio_pci_cap64 {
+        struct virtio_pci_cap cap;
+        u32 offset_hi;
+        u32 length_hi;
+};
+\end{lstlisting}
+
+Given that the \field{cap.length} and \field{cap.offset} fields
+are only 32 bit, the additional \field{offset_hi} and \field {length_hi}
+fields provide the most significant 32 bits of a total 64 bit offset and
+length within the bar specified by \field{cap.bar}.
+
 \drivernormative{\subsubsection}{Virtio Structure PCI Capabilities}{Virtio Transport Options / Virtio Over PCI Bus / Virtio Structure PCI Capabilities}
 
 The driver MUST ignore any vendor-specific capability structure which has
-- 
2.21.0


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