On Mon, 3 Mar 2025, Nicholas Piggin wrote:
Perform !guest_visible memory accesses without modifying R/C bits.
It's arguable whether !guest_visible memory accesses should modify
R/C bits. i386 seems to set accessed/dirty bit updates for "probe"
accesses, but ppc with radix MMU does not. Follow the ppc/radix
lead and perform the accesses without updating R/C bits.
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
target/ppc/mmu-hash32.c | 27 ++++++++++++++-------------
target/ppc/mmu-hash64.c | 27 ++++++++++++++-------------
2 files changed, 28 insertions(+), 26 deletions(-)
diff --git a/target/ppc/mmu-hash32.c b/target/ppc/mmu-hash32.c
index 1f791a7f2f7..b8d7f87507b 100644
--- a/target/ppc/mmu-hash32.c
+++ b/target/ppc/mmu-hash32.c
@@ -410,19 +410,20 @@ bool ppc_hash32_xlate(PowerPCCPU *cpu, vaddr eaddr,
MMUAccessType access_type,
qemu_log_mask(CPU_LOG_MMU, "PTE access granted !\n");
/* 8. Update PTE referenced and changed bits if necessary */
-
- if (!(pte.pte1 & HPTE32_R_R)) {
- ppc_hash32_set_r(cpu, pte_offset, pte.pte1);
- }
- if (!(pte.pte1 & HPTE32_R_C)) {
- if (access_type == MMU_DATA_STORE) {
- ppc_hash32_set_c(cpu, pte_offset, pte.pte1);
- } else {
- /*
- * Treat the page as read-only for now, so that a later write
- * will pass through this function again to set the C bit
- */
- prot &= ~PAGE_WRITE;
+ if (guest_visible) {
Are these unlikely() ? Not sure if that makes a difference but if we know
it may help some compilers.
Regards,
BALATON Zoltan
+ if (!(pte.pte1 & HPTE32_R_R)) {
+ ppc_hash32_set_r(cpu, pte_offset, pte.pte1);
+ }
+ if (!(pte.pte1 & HPTE32_R_C)) {
+ if (access_type == MMU_DATA_STORE) {
+ ppc_hash32_set_c(cpu, pte_offset, pte.pte1);
+ } else {
+ /*
+ * Treat the page as read-only for now, so that a later write
+ * will pass through this function again to set the C bit
+ */
+ prot &= ~PAGE_WRITE;
+ }
}
}
*protp = prot;
diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
index 5ca4faee2ab..de5eb5fb221 100644
--- a/target/ppc/mmu-hash64.c
+++ b/target/ppc/mmu-hash64.c
@@ -1183,19 +1183,20 @@ bool ppc_hash64_xlate(PowerPCCPU *cpu, vaddr eaddr,
MMUAccessType access_type,
qemu_log_mask(CPU_LOG_MMU, "PTE access granted !\n");
/* 6. Update PTE referenced and changed bits if necessary */
-
- if (!(pte.pte1 & HPTE64_R_R)) {
- ppc_hash64_set_r(cpu, ptex, pte.pte1);
- }
- if (!(pte.pte1 & HPTE64_R_C)) {
- if (access_type == MMU_DATA_STORE) {
- ppc_hash64_set_c(cpu, ptex, pte.pte1);
- } else {
- /*
- * Treat the page as read-only for now, so that a later write
- * will pass through this function again to set the C bit
- */
- prot &= ~PAGE_WRITE;
+ if (guest_visible) {
+ if (!(pte.pte1 & HPTE64_R_R)) {
+ ppc_hash64_set_r(cpu, ptex, pte.pte1);
+ }
+ if (!(pte.pte1 & HPTE64_R_C)) {
+ if (access_type == MMU_DATA_STORE) {
+ ppc_hash64_set_c(cpu, ptex, pte.pte1);
+ } else {
+ /*
+ * Treat the page as read-only for now, so that a later write
+ * will pass through this function again to set the C bit
+ */
+ prot &= ~PAGE_WRITE;
+ }
}
}
