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由 H. Peter Anvin 提交于
Patch 5a5a51db x86-32: Start out eflags and cr4 clean ... made x86-32 match x86-64 in that we initialize %eflags and %cr4 from scratch. This broke OLPC XO-1.5, because the XO enters the kernel with paging enabled, which the kernel doesn't expect. Since we no longer support 386 (the source of most of the variability in %cr0 configuration), we can simply match further x86-64 and initialize %cr0 to a fixed value -- the one variable part remaining in %cr0 is for FPU control, but all that is handled later on in initialization; in particular, configuring %cr0 as if the FPU is present until proven otherwise is correct and necessary for the probe to work. To deal with the XO case sanely, explicitly disable paging in %cr0 before we muck with %cr3, %cr4 or EFER -- those operations are inherently unsafe with paging enabled. NOTE: There is still a lot of 386-related junk in head_32.S which we can and should get rid of, however, this is intended as a minimal fix whereas the cleanup can be deferred to the next merge window. Reported-by: NAndres Salomon <dilinger@queued.net> Tested-by: NDaniel Drake <dsd@laptop.org> Link: http://lkml.kernel.org/r/50FA0661.2060400@linux.intel.comSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>
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