[vbox-dev] Problem with kernel 5.8

[Frank Batschulat]

Larry, thanks - this work will be tracked with:

Ticket #19644 (accepted defect)
Linux kernel version: 5.8 - we need changes
https://www.virtualbox.org/ticket/19644


On Fri, 05 Jun 2020 23:39:08 +0200, Larry Finger  
<Larry.Finger at lwfinger.net> wrote:

> In a little over one week, Linus will release Kernel 5.8.0-rc1. Shortly  
> thereafter, openSUSE Tumbleweed will start builds using that kernel.  
> Unless I have patched our copy of the code for the VB kernel modules, my  
> mailbox will be flooded with build failure messages.
>
> Thus far, I have found two incompatibilities with the 5.8 APIs. The  
> first was the removal of __get_vm_area(). This one can be trivially  
> replaced with __get_vm_area_caller(), which has one additional argument  
> that is always "__builtin_return_address(0)."
>
> A second API change is more complicated, and above my understanding. In  
> the associated patch entitled "mm: only allow page table mappings for  
> built-in zsmalloc", symbols map_vm_area() and unmap_kernel_range() are  
> no longer exported. The first of these are used in this snippet found in  
> src/vboxdrv/r0drv/linux/alloc-r0drv-linux.c:
>
>      if (iPage == cPages)
>      {
>          /*
>           * Map the pages.
>           *
>           * Not entirely sure we really need to set nr_pages and pages  
> here, but
>           * they provide a very convenient place for storing something  
> we need
>           * in the free function, if nothing else...
>           */
> # if LINUX_VERSION_CODE < KERNEL_VERSION(3, 17, 0)
>          struct page **papPagesIterator = papPages;
> # endif
>          pVmArea->nr_pages = cPages;
>          pVmArea->pages    = papPages;
>          if (!map_vm_area(pVmArea, PAGE_KERNEL_EXEC,
> # if LINUX_VERSION_CODE < KERNEL_VERSION(3, 17, 0)
>                           &papPagesIterator
> # else
>                           papPages
> # endif
>                           ))
>          {
>              PRTMEMLNXHDREX pHdrEx = (PRTMEMLNXHDREX)pVmArea->addr;
>              pHdrEx->pVmArea     = pVmArea;
>              pHdrEx->pvDummy     = NULL;
>              return &pHdrEx->Hdr;
>          }
>          /* bail out */
> # if LINUX_VERSION_CODE < KERNEL_VERSION(3, 17, 0)
>          pVmArea->nr_pages = papPagesIterator - papPages;
> # endif
>      }
>
> I think the code could use vm_map_ram() to map the papPages array  
> directly, but I would appreciate any help the developers could provide.
>
> Thanks,
>
> Larry
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-- 
frankB

Oracle Virtualbox Development