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[v4,1/7] target/riscv: Don't set write permissions on dirty PTEs

Message ID 6532e1a327feada5bbd0631ed6ea72ec32528936.1566573576.git.alistair.francis@wdc.com (mailing list archive)
State New, archived
Headers show
Series RISC-V: Hypervisor prep work part 2 | expand

Commit Message

Alistair Francis Aug. 23, 2019, 3:21 p.m. UTC 
Setting write permission on dirty PTEs results in userspace inside a
Hypervisor guest (VU) becoming corrupted. This appears to be because it
ends up with write permission in the second stage translation in cases
where we aren't doing a store.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
---
 target/riscv/cpu_helper.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)
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Patch

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index e32b6126af..f027be7f16 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -340,10 +340,8 @@  restart:
             if ((pte & PTE_X)) {
                 *prot |= PAGE_EXEC;
             }
-            /* add write permission on stores or if the page is already dirty,
-               so that we TLB miss on later writes to update the dirty bit */
-            if ((pte & PTE_W) &&
-                    (access_type == MMU_DATA_STORE || (pte & PTE_D))) {
+            /* add write permission on stores */
+            if ((pte & PTE_W) && (access_type == MMU_DATA_STORE)) {
                 *prot |= PAGE_WRITE;
             }
             return TRANSLATE_SUCCESS;