[PATCH v6 4/4] target/riscv: Change the TLB page size depends on PMP entries.

[Zong Li]

The minimum granularity of PMP is 4 bytes, it is small than 4KB page
size, therefore, the pmp checking would be ignored if its range doesn't
start from the alignment of one page. This patch detects the pmp entries
and sets the small page size to TLB if there is a PMP entry which cover
the page size.

Signed-off-by: Zong Li <zong.li@sifive.com>
---
 target/riscv/cpu_helper.c | 10 ++++++--
 target/riscv/pmp.c        | 52 +++++++++++++++++++++++++++++++++++++++
 target/riscv/pmp.h        |  2 ++
 3 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 2f337e418c..fd1d373b6f 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -693,6 +693,7 @@ bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int 
size,
     bool first_stage_error = true;
     int ret = TRANSLATE_FAIL;
     int mode = mmu_idx;
+    target_ulong tlb_size = 0;
 
     env->guest_phys_fault_addr = 0;
 
@@ -784,8 +785,13 @@ bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int 
size,
     }
 
     if (ret == TRANSLATE_SUCCESS) {
-        tlb_set_page(cs, address & TARGET_PAGE_MASK, pa & TARGET_PAGE_MASK,
-                     prot, mmu_idx, TARGET_PAGE_SIZE);
+        if (pmp_is_range_in_tlb(env, pa & TARGET_PAGE_MASK, &tlb_size)) {
+            tlb_set_page(cs, address & ~(tlb_size - 1), pa & ~(tlb_size - 1),
+                         prot, mmu_idx, tlb_size);
+        } else {
+            tlb_set_page(cs, address & TARGET_PAGE_MASK, pa & TARGET_PAGE_MASK,
+                         prot, mmu_idx, TARGET_PAGE_SIZE);
+        }
         return true;
     } else if (probe) {
         return false;
diff --git a/target/riscv/pmp.c b/target/riscv/pmp.c
index aeba796484..adadf6e9ba 100644
--- a/target/riscv/pmp.c
+++ b/target/riscv/pmp.c
@@ -393,3 +393,55 @@ target_ulong pmpaddr_csr_read(CPURISCVState *env, uint32_t 
addr_index)
 
     return val;
 }
+
+/*
+ * Calculate the TLB size if the start address or the end address of
+ * PMP entry is presented in thie TLB page.
+ */
+static target_ulong pmp_get_tlb_size(CPURISCVState *env, int pmp_index,
+    target_ulong tlb_sa, target_ulong tlb_ea)
+{
+    target_ulong pmp_sa = env->pmp_state.addr[pmp_index].sa;
+    target_ulong pmp_ea = env->pmp_state.addr[pmp_index].ea;
+
+    if (pmp_sa >= tlb_sa && pmp_ea <= tlb_ea) {
+        return pmp_ea - pmp_sa + 1;
+    }
+
+    if (pmp_sa >= tlb_sa && pmp_sa <= tlb_ea && pmp_ea >= tlb_ea) {
+        return tlb_ea - pmp_sa + 1;
+    }
+
+    if (pmp_ea <= tlb_ea && pmp_ea >= tlb_sa && pmp_sa <= tlb_sa) {
+        return pmp_ea - tlb_sa + 1;
+    }
+
+    return 0;
+}
+
+/*
+ * Check is there a PMP entry whcih range covers this page. If so,
+ * try to find the minimum granularity for the TLB size.
+ */
+bool pmp_is_range_in_tlb(CPURISCVState *env, hwaddr tlb_sa,
+    target_ulong *tlb_size)
+{
+    int i;
+    target_ulong val;
+    target_ulong tlb_ea = (tlb_sa + TARGET_PAGE_SIZE - 1);
+
+    for (i = 0; i < MAX_RISCV_PMPS; i++) {
+        val = pmp_get_tlb_size(env, i, tlb_sa, tlb_ea);
+        if (val) {
+            if (*tlb_size == 0 || *tlb_size > val) {
+                *tlb_size = val;
+            }
+        }
+    }
+
+    if (*tlb_size != 0) {
+        return true;
+    }
+
+    return false;
+}
diff --git a/target/riscv/pmp.h b/target/riscv/pmp.h
index 8e19793132..c70f2ea4c4 100644
--- a/target/riscv/pmp.h
+++ b/target/riscv/pmp.h
@@ -60,5 +60,7 @@ void pmpaddr_csr_write(CPURISCVState *env, uint32_t 
addr_index,
 target_ulong pmpaddr_csr_read(CPURISCVState *env, uint32_t addr_index);
 bool pmp_hart_has_privs(CPURISCVState *env, target_ulong addr,
     target_ulong size, pmp_priv_t priv, target_ulong mode);
+bool pmp_is_range_in_tlb(CPURISCVState *env, hwaddr tlb_sa,
+    target_ulong *tlb_size);
 
 #endif
-- 
2.27.0