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c2863febd8
A PFN is not secure enough to promise that the memory is not IO. And direct access via memcpy() that only handles CPU memory will crash on S390 if the PFN is an IO PFN, as we have to use the memcpy_to/fromio() that uses the special S390 IO access instructions. On the other hand, a "struct page *" is always a CPU coherent thing that fits memcpy(). Also, casting a PFN to "void *" for memcpy() is not a proper practice, kmap_local_page() is the correct API to call here, though S390 doesn't use highmem, which means kmap_local_page() is a NOP. There's a following patch changing the vfio_pin_pages() API to return a list of "struct page *" instead of PFNs. It will block any IO memory from ever getting into this call path, for such a security purpose. In this patch, add kmap_local_page() to prepare for that. Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Acked-by: Eric Farman <farman@linux.ibm.com> Tested-by: Eric Farman <farman@linux.ibm.com> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com> Link: https://lore.kernel.org/r/20220723020256.30081-10-nicolinc@nvidia.com Signed-off-by: Alex Williamson <alex.williamson@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.