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a72cac6067
In some cases, the access to the virtqueue's descriptor area, device and driver areas (precluding indirect descriptor table in guest memory) may have to be confined to a different address space than where its buffers reside. Without loss of simplicity and generality with already established terminology, let's fold up these 3 areas and call them as a whole as descriptor table group, or descriptor group for short. Specifically, in case of split virtqueues, descriptor group consists of regions for Descriptor Table, Available Ring and Used Ring; for packed virtqueues layout, descriptor group contains Descriptor Ring, Driver and Device Event Suppression structures. The group ID for a dedicated descriptor group can be obtained through a new .get_vq_desc_group() op. If driver implements this op, it means that the descriptor, device and driver areas of the virtqueue may reside in a dedicated group than where its buffers reside, a.k.a the default virtqueue group through the .get_vq_group() op. In principle, the descriptor group may or may not have same group ID as the default group. Even if the descriptor group has a different ID, meaning the vq's descriptor group areas can optionally move to a separate address space than where guest memory resides, the descriptor group may still start from a default address space, same as where its buffers reside. To move the descriptor group to a different address space, .set_group_asid() has to be called to change the ASID binding for the group, which is no different than what needs to be done on any other virtqueue group. On the other hand, the .reset() semantics also applies on descriptor table group, meaning the device reset will clear all ASID bindings and move all virtqueue groups including descriptor group back to the default address space, i.e. in ASID 0. QEMU's shadow virtqueue is going to utilize dedicated descriptor group to speed up map and unmap operations, yielding tremendous downtime reduction by avoiding the full and slow remap cycle in SVQ switching. Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com> Acked-by: Eugenio Pérez <eperezma@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Message-Id: <20231018171456.1624030-4-dtatulea@nvidia.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Si-Wei Liu <si-wei.liu@oracle.com> Tested-by: Si-Wei Liu <si-wei.liu@oracle.com> Tested-by: Lei Yang <leiyang@redhat.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.