x86/mm: Do not use set_{pud, pmd}_safe() when splitting a large page

The commit

  0a9fe8ca844d ("x86/mm: Validate kernel_physical_mapping_init() PTE population")

triggers this warning in SEV guests:

  WARNING: CPU: 0 PID: 0 at arch/x86/include/asm/pgalloc.h:87 phys_pmd_init+0x30d/0x386
  Call Trace:
   kernel_physical_mapping_init+0xce/0x259
   early_set_memory_enc_dec+0x10f/0x160
   kvm_smp_prepare_boot_cpu+0x71/0x9d
   start_kernel+0x1c9/0x50b
   secondary_startup_64+0xa4/0xb0

A SEV guest calls kernel_physical_mapping_init() to clear the encryption
mask from an existing mapping. While doing so, it also splits large
pages into smaller.

To split a page, kernel_physical_mapping_init() allocates a new page and
updates the existing entry. The set_{pud,pmd}_safe() helpers trigger a
warning when updating an entry with a page in the present state.

Add a new kernel_physical_mapping_change() helper which uses the
non-safe variants of set_{pmd,pud,p4d}() and {pmd,pud,p4d}_populate()
routines when updating the entry.

Since kernel_physical_mapping_change() may replace an existing
entry with a new entry, the caller is responsible to flush
the TLB at the end. Change early_set_memory_enc_dec() to use
kernel_physical_mapping_change() when it wants to clear the memory
encryption mask from the page table entry.

 [ bp:
   - massage commit message.
   - flesh out comment according to dhansen's request.
   - align function arguments at opening brace. ]

Fixes: 0a9fe8ca844d ("x86/mm: Validate kernel_physical_mapping_init() PTE population")
Signed-off-by: Brijesh Singh <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Dave Hansen <[email protected]>
Acked-by:  Peter Zijlstra (Intel) <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Thomas Lendacky <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions