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2a8a8afba0
vmbus_reserve_fb() tries reserving framebuffer region iff 'screen_info.lfb_base' is set. Gen2 VMs seem to have it set by EFI and/or by the kernel EFI FB driver (or, in some edge cases like kexec, the address where the buffer was moved, see https://lore.kernel.org/all/20201014092429.1415040-1-kasong@redhat.com/) but on Gen1 VM it depends on bootloader behavior. With grub, it depends on 'gfxpayload=' setting but in some cases it is observed to be zero. That being said, relying on 'screen_info.lfb_base' to reserve framebuffer region is risky. For Gen1 VMs, it should always be possible to get the address from the dedicated PCI device instead. Check for legacy PCI video device presence and reserve the whole region for framebuffer on Gen1 VMs. Reviewed-by: Michael Kelley <mikelley@microsoft.com> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Link: https://lore.kernel.org/r/20220827130345.1320254-3-vkuznets@redhat.com Signed-off-by: Wei Liu <wei.liu@kernel.org>
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.