Commit c5b367835cfc ("MIPS: Add support for XPA.") changed
build_pte_present() and build_pte_writable() to assume a constant offset
of _PAGE_READ and _PAGE_WRITE relative to _PAGE_PRESENT, however this is
no longer true for some MIPS32R2 builds since commit be0c37c985ed
("MIPS: Rearrange PTE bits into fixed positions.") which moved the
_PAGE_READ PTE bit away from the _PAGE_PRESENT bit, with the _PAGE_WRITE
bit falling into its place.
Make use of the _PAGE_READ and _PAGE_WRITE definitions to calculate the
correct mask to apply instead of hard coding 3 (for _PAGE_PRESENT |
_PAGE_READ) or 5 (for _PAGE_PRESENT | _PAGE_WRITE).
Fixes: c5b367835cfc ("MIPS: Add support for XPA.")
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Steven J. Hill <Steven.Hill@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
---
I hit a hang during boot on v4.1-rc1 KVM guest kernels, where its
continuously trying to service a TLB miss for a page which is apparently
_PAGE_READ but not _PAGE_WRITE, but since the TLBL handler
(build_pte_present()) ends up incorrectly testing _PAGE_WRITE, it just
keeps calling into C code instead of making the PTE valid and updating
the TLB entry.
The build_pte_present() part of this patch fixes it, but its still not
entirely clear to me why I cannot reproduce the problem in other MIPS R2
environments without RIXI.
---
arch/mips/mm/tlbex.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 97c87027c17f..d998fea7fc93 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -1623,8 +1623,10 @@ build_pte_present(u32 **p, struct uasm_reloc **r,
}
} else {
uasm_i_srl(p, t, pte, _PAGE_PRESENT_SHIFT);
- uasm_i_andi(p, t, t, 3);
- uasm_i_xori(p, t, t, 3);
+ uasm_i_andi(p, t, t,
+ (_PAGE_PRESENT | _PAGE_READ) >> _PAGE_PRESENT_SHIFT);
+ uasm_i_xori(p, t, t,
+ (_PAGE_PRESENT | _PAGE_READ) >> _PAGE_PRESENT_SHIFT);
uasm_il_bnez(p, r, t, lid);
if (pte == t)
/* You lose the SMP race :-(*/
@@ -1654,8 +1656,10 @@ build_pte_writable(u32 **p, struct uasm_reloc **r,
int t = scratch >= 0 ? scratch : pte;
uasm_i_srl(p, t, pte, _PAGE_PRESENT_SHIFT);
- uasm_i_andi(p, t, t, 5);
- uasm_i_xori(p, t, t, 5);
+ uasm_i_andi(p, t, t,
+ (_PAGE_PRESENT | _PAGE_WRITE) >> _PAGE_PRESENT_SHIFT);
+ uasm_i_xori(p, t, t,
+ (_PAGE_PRESENT | _PAGE_WRITE) >> _PAGE_PRESENT_SHIFT);
uasm_il_bnez(p, r, t, lid);
if (pte == t)
/* You lose the SMP race :-(*/
--
2.0.5
