[PULL,05/32] RISC-V: Only Check PMP if MMU translation succeeds

Commit Message

Palmer Dabbelt July 3, 2019, 8:40 a.m. UTC

From: Hesham Almatary <[e-mail]>

The current implementation unnecessarily checks for PMP even if MMU translation
failed. This may trigger a wrong PMP access exception instead of
a page exception.

For example, the very first instruction fetched after the first satp write in
S-Mode will trigger a PMP access fault instead of an instruction fetch page
fault.

This patch prioritises MMU exceptions over PMP exceptions and only checks for
PMP if MMU translation succeeds. This patch is required for future commits
that properly report PMP exception violations if PTW succeeds.

Signed-off-by: Hesham Almatary <[e-mail]>
Reviewed-by: Alistair Francis <[e-mail]>
Signed-off-by: Palmer Dabbelt <[e-mail]>
---
 target/riscv/cpu_helper.c | 1 +
 1 file changed, 1 insertion(+)

Patch

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 0bbfb7f48b79..a45b05ef8395 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -436,6 +436,7 @@  bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
                   " prot %d\n", __func__, address, ret, pa, prot);
 
     if (riscv_feature(env, RISCV_FEATURE_PMP) &&
+        (ret == TRANSLATE_SUCCESS) &&
         !pmp_hart_has_privs(env, pa, TARGET_PAGE_SIZE, 1 << access_type)) {
         ret = TRANSLATE_FAIL;
     }