On 6/20/2017 3:55 PM, Thomas Gleixner wrote:
On Fri, 16 Jun 2017, Tom Lendacky wrote:
Currently there is a check if the address being mapped is in the ISA
range (is_ISA_range()), and if it is then phys_to_virt() is used to
perform the mapping. When SME is active, however, this will result
in the mapping having the encryption bit set when it is expected that
an ioremap() should not have the encryption bit set. So only use the
phys_to_virt() function if SME is not active
This does not make sense to me. What the heck has phys_to_virt() to do with
the encryption bit. Especially why would the encryption bit be set on that
mapping in the first place?
The default is that all entries that get added to the pagetables have
the encryption bit set unless specifically overridden. Any __va() or
phys_to_virt() calls will result in a pagetable mapping that has the
encryption bit set. For ioremap, the PAGE_KERNEL_IO protection is used
which will not/does not have the encryption bit set.
I'm probably missing something, but this want's some coherent explanation
understandable by mere mortals both in the changelog and the code comment.
I'll add some additional info to the changelog and code.
Thanks,
Tom
Thanks,
tglx
