core: riscv: Fix PTE creation when freeing PTE

The core_mmu_pte_create() is also called when MM core frees the pages,
which means the PTE should be zero. Current implementation always sets
valid bit (V), which is not proper way when clearing PTE. Fix it by only
honoring pte_bits parameter, which may be constructed in
mattr_to_pte_bits().

The core_mmu_ptp_create() is used to create non-leaf PTE, which points
to the next level of the page table. According to RISC-V privilege Spec,
non-leaf PTE only needs V bit. Therefore, we just give the V bit to
core_mmu_pte_create() when we want to create non-leaf PTE.

Signed-off-by: Alvin Chang <alvinga@andestech.com>
Reviewed-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Marouene Boubakri <marouene.boubakri@nxp.com>

Author: gagachang

core/arch/riscv/mm/core_mmu_arch.c

@@ -113,15 +113,23 @@ static bool __maybe_unused core_mmu_entry_is_branch(struct mmu_pte *pte)
 	return !core_mmu_entry_is_leaf(pte);
 }
 
-static unsigned long core_mmu_pte_create(unsigned long ppn, uint8_t perm)
+static unsigned long core_mmu_pte_create(unsigned long ppn, uint8_t pte_bits)
 {
-	return SHIFT_U64(ppn, PTE_PPN_SHIFT) | PTE_V | perm;
+	/*
+	 * This function may be called from core_mmu_set_entry(). There is a
+	 * case that MM core wants to clear PTE by calling core_mmu_set_entry()
+	 * with zero physical address and zero memory attributes, which turns
+	 * @ppn and @pte_bits in this function to be both zero. In this case, we
+	 * should create zero PTE without setting its V bit.
+	 */
+
+	return SHIFT_U64(ppn, PTE_PPN_SHIFT) | pte_bits;
 }
 
 static unsigned long core_mmu_ptp_create(unsigned long ppn)
 {
-	/* set perms to 0 since core_mmu_pte_create() already adds PTE_V */
-	return core_mmu_pte_create(ppn, 0);
+	/* Set V bit to create PTE points to next level of the page table. */
+	return core_mmu_pte_create(ppn, PTE_V);
 }
 
 static unsigned long core_mmu_pte_ppn(struct mmu_pte *pte)