Author: jhb
Date: Mon Nov 5 20:00:36 2018
New Revision: 340159
URL: https://svnweb.freebsd.org/changeset/base/340159
Log:
Rework setting PTE_D for kernel mappings.
Rather than unconditionally setting PTE_D for all writeable kernel
mappings, set PTE_D for writable mappings of unmanaged pages (whether
user or kernel). This matches what amd64 does and also matches what
the RISC-V spec suggests (preset the A and D bits on mappings where
the OS doesn't care about the state).
Suggested by: alc
Reviewed by: alc, markj
Sponsored by: DARPA
Modified:
head/sys/riscv/riscv/pmap.c
Modified: head/sys/riscv/riscv/pmap.c
==============================================================================
--- head/sys/riscv/riscv/pmap.c Mon Nov 5 19:51:16 2018 (r340158)
+++ head/sys/riscv/riscv/pmap.c Mon Nov 5 20:00:36 2018 (r340159)
@@ -2098,13 +2098,20 @@ pmap_enter(pmap_t pmap, vm_offset_t va, vm_page_t m, v
new_l3 |= PTE_W;
if ((va >> 63) == 0)
new_l3 |= PTE_U;
- else if (prot & VM_PROT_WRITE)
- new_l3 |= PTE_D;
new_l3 |= (pn << PTE_PPN0_S);
if ((flags & PMAP_ENTER_WIRED) != 0)
new_l3 |= PTE_SW_WIRED;
- if ((m->oflags & VPO_UNMANAGED) == 0)
+
+ /*
+ * Set modified bit gratuitously for writeable mappings if
+ * the page is unmanaged. We do not want to take a fault
+ * to do the dirty bit accounting for these mappings.
+ */
+ if ((m->oflags & VPO_UNMANAGED) != 0) {
+ if (prot & VM_PROT_WRITE)
+ new_l3 |= PTE_D;
+ } else
new_l3 |= PTE_SW_MANAGED;
CTR2(KTR_PMAP, "pmap_enter: %.16lx -> %.16lx", va, pa);
_______________________________________________
svn-src-all@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
