While discussing a problem with how we're (not) setting vstart_eq_zero
Richard had the following to say w.r.t the conditional mark_vs_dirty()
calls on load/store functions [1]:
"I think it's required to have stores set dirty unconditionally, before
the operation.
Consider a store that traps on the 2nd element, leaving vstart = 2, and
exiting to the main loop via exception. The exception enters the kernel
page fault handler. The kernel may need to fault in the page for the
process, and in the meantime task switch.
If vs dirty is not already set, the kernel won't know to save vector
state on task switch."
Do a mark_vs_dirty() before store operations. Keep the mark_vs_dirty()
call at the end for loads - the function is a no-op if mstatus_vs is
already set to EXT_STATUS_DIRTY so there's no hurt in store functions
calling it twice.
[1]
72c7503b-0f43-44b8-aa82-fbafed2aac0c@linaro.org/">https://lore.kernel.org/qemu-riscv/72c7503b-0f43-44b8-aa82-fbafed2aac0c@linaro.org/
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
target/riscv/insn_trans/trans_rvv.c.inc | 29 +++++++++++++++----------
1 file changed, 17 insertions(+), 12 deletions(-)
diff --git a/target/riscv/insn_trans/trans_rvv.c.inc
b/target/riscv/insn_trans/trans_rvv.c.inc
index 9e101ab434..2065e9064e 100644
--- a/target/riscv/insn_trans/trans_rvv.c.inc
+++ b/target/riscv/insn_trans/trans_rvv.c.inc
@@ -636,12 +636,13 @@ static bool ldst_us_trans(uint32_t vd, uint32_t rs1,
uint32_t data,
tcg_gen_addi_ptr(dest, tcg_env, vreg_ofs(s, vd));
tcg_gen_addi_ptr(mask, tcg_env, vreg_ofs(s, 0));
- fn(dest, mask, base, tcg_env, desc);
-
- if (!is_store) {
+ if (is_store) {
mark_vs_dirty(s);
}
+ fn(dest, mask, base, tcg_env, desc);
+
+ mark_vs_dirty(s);