git: 2649bef7e4ab - stable/13 - riscv: Add a stub pmap_change_attr implementation

The branch stable/13 has been updated by jrtc27:

URL: https://cgit.FreeBSD.org/src/commit/?id=2649bef7e4abbe977c7ff8fef1f1f65c1131ba01

commit 2649bef7e4abbe977c7ff8fef1f1f65c1131ba01
Author:     Jessica Clarke <jrtc27@FreeBSD.org>
AuthorDate: 2021-10-03 18:33:47 +0000
Commit:     Jessica Clarke <jrtc27@FreeBSD.org>
CommitDate: 2021-10-10 13:36:52 +0000

    riscv: Add a stub pmap_change_attr implementation
    
    pmap_change_attr is required by drm-kmod so we need the function to
    exist. Since the Svpbmt extension is on the horizon we will likely end
    up with a real implementation of it, so this stub implementation does
    all the necessary page table walking to validate the input, ensuring
    that no new errors are returned once it's implemented fully (other than
    due to out of memory conditions when demoting L2 entries) and providing
    a skeleton for that future implementation.
    
    Reviewed by:    markj
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D31996
    
    (cherry picked from commit 1be2e16df1d29148aee83964330a71ae403c6078)
---
 sys/riscv/include/pmap.h |  1 +
 sys/riscv/riscv/pmap.c   | 94 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+)

diff --git a/sys/riscv/include/pmap.h b/sys/riscv/include/pmap.h
index 599adfa4ce19..024bc3743f67 100644
--- a/sys/riscv/include/pmap.h
+++ b/sys/riscv/include/pmap.h
@@ -144,6 +144,7 @@ struct thread;
 void	pmap_activate_boot(pmap_t);
 void	pmap_activate_sw(struct thread *);
 void	pmap_bootstrap(vm_offset_t, vm_paddr_t, vm_size_t);
+int	pmap_change_attr(vm_offset_t va, vm_size_t size, int mode);
 void	pmap_kenter_device(vm_offset_t, vm_size_t, vm_paddr_t);
 vm_paddr_t pmap_kextract(vm_offset_t va);
 void	pmap_kremove(vm_offset_t);
diff --git a/sys/riscv/riscv/pmap.c b/sys/riscv/riscv/pmap.c
index b60df135fd51..c596ce15bde5 100644
--- a/sys/riscv/riscv/pmap.c
+++ b/sys/riscv/riscv/pmap.c
@@ -310,6 +310,8 @@ static void _pmap_unwire_ptp(pmap_t pmap, vm_offset_t va, vm_page_t m,
     struct spglist *free);
 static int pmap_unuse_pt(pmap_t, vm_offset_t, pd_entry_t, struct spglist *);
 
+static int pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode);
+
 #define	pmap_clear(pte)			pmap_store(pte, 0)
 #define	pmap_clear_bits(pte, bits)	atomic_clear_64(pte, bits)
 #define	pmap_load_store(pte, entry)	atomic_swap_64(pte, entry)
@@ -4252,6 +4254,98 @@ pmap_page_set_memattr(vm_page_t m, vm_memattr_t ma)
 {
 
 	m->md.pv_memattr = ma;
+
+	/*
+	 * If "m" is a normal page, update its direct mapping.  This update
+	 * can be relied upon to perform any cache operations that are
+	 * required for data coherence.
+	 */
+	if ((m->flags & PG_FICTITIOUS) == 0 &&
+	    pmap_change_attr(PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m)), PAGE_SIZE,
+	    m->md.pv_memattr) != 0)
+		panic("memory attribute change on the direct map failed");
+}
+
+/*
+ * Changes the specified virtual address range's memory type to that given by
+ * the parameter "mode".  The specified virtual address range must be
+ * completely contained within either the direct map or the kernel map.
+ *
+ * Returns zero if the change completed successfully, and either EINVAL or
+ * ENOMEM if the change failed.  Specifically, EINVAL is returned if some part
+ * of the virtual address range was not mapped, and ENOMEM is returned if
+ * there was insufficient memory available to complete the change.  In the
+ * latter case, the memory type may have been changed on some part of the
+ * virtual address range.
+ */
+int
+pmap_change_attr(vm_offset_t va, vm_size_t size, int mode)
+{
+	int error;
+
+	PMAP_LOCK(kernel_pmap);
+	error = pmap_change_attr_locked(va, size, mode);
+	PMAP_UNLOCK(kernel_pmap);
+	return (error);
+}
+
+static int
+pmap_change_attr_locked(vm_offset_t va, vm_size_t size, int mode)
+{
+	vm_offset_t base, offset, tmpva;
+	pd_entry_t *l1, l1e;
+	pd_entry_t *l2, l2e;
+	pt_entry_t *l3, l3e;
+
+	PMAP_LOCK_ASSERT(kernel_pmap, MA_OWNED);
+	base = trunc_page(va);
+	offset = va & PAGE_MASK;
+	size = round_page(offset + size);
+
+	if (!VIRT_IN_DMAP(base) &&
+	    !(base >= VM_MIN_KERNEL_ADDRESS && base < VM_MAX_KERNEL_ADDRESS))
+		return (EINVAL);
+
+	for (tmpva = base; tmpva < base + size; ) {
+		l1 = pmap_l1(kernel_pmap, tmpva);
+		if (l1 == NULL || ((l1e = pmap_load(l1)) & PTE_V) == 0)
+			return (EINVAL);
+		if ((l1e & PTE_RWX) != 0) {
+			/*
+			 * TODO: Demote if attributes don't match and there
+			 * isn't an L1 page left in the range, and update the
+			 * L1 entry if the attributes don't match but there is
+			 * an L1 page left in the range, once we support the
+			 * upcoming Svpbmt extension.
+			 */
+			tmpva = (tmpva & ~L1_OFFSET) + L1_SIZE;
+			continue;
+		}
+		l2 = pmap_l1_to_l2(l1, tmpva);
+		if (l2 == NULL || ((l2e = pmap_load(l2)) & PTE_V) == 0)
+			return (EINVAL);
+		if ((l2e & PTE_RWX) != 0) {
+			/*
+			 * TODO: Demote if attributes don't match and there
+			 * isn't an L2 page left in the range, and update the
+			 * L2 entry if the attributes don't match but there is
+			 * an L2 page left in the range, once we support the
+			 * upcoming Svpbmt extension.
+			 */
+			tmpva = (tmpva & ~L2_OFFSET) + L2_SIZE;
+			continue;
+		}
+		l3 = pmap_l2_to_l3(l2, tmpva);
+		if (l3 == NULL || ((l3e = pmap_load(l3)) & PTE_V) == 0)
+			return (EINVAL);
+		/*
+		 * TODO: Update the L3 entry if the attributes don't match once
+		 * we support the upcoming Svpbmt extension.
+		 */
+		tmpva += PAGE_SIZE;
+	}
+
+	return (0);
 }
 
 /*