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[PATCH v2] target/riscv: Call probe_write() before atomic operations
From: |
Alistair Francis |
Subject: |
[PATCH v2] target/riscv: Call probe_write() before atomic operations |
Date: |
Fri, 1 Apr 2022 11:49:20 +1000 |
From: Alistair Francis <alistair.francis@wdc.com>
If an atomic operation fails on RISC-V we want to generate a store/amo
fault and not a load fault.
Currently if we have no permissions to access the memory location the
atomic operation will sometimes fail with a load fault (depending on the
path taken in tcg/tcg-op.c) as the atomic helpers perform a load then a
store.
By performing a probe_write() on the memory first, we can ensure we have
permissions to perform the atomic operation. As RISC-V doesn't have
write only pages this should be pretty robust (PMP might be the
exception).
Note that this only fixes the fault for memory regions. I/O and
non-existant regions will still trigger a load fault.
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
target/riscv/cpu.h | 2 ++
target/riscv/helper.h | 2 ++
target/riscv/cpu_helper.c | 2 +-
target/riscv/op_helper.c | 14 ++++++++++++++
target/riscv/insn_trans/trans_rva.c.inc | 3 +++
5 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index c069fe85fa..c215cd1b6a 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -179,6 +179,8 @@ struct CPUArchState {
uint64_t mie;
uint64_t mideleg;
+ bool amo_store_fault;
+
target_ulong satp; /* since: priv-1.10.0 */
target_ulong stval;
target_ulong medeleg;
diff --git a/target/riscv/helper.h b/target/riscv/helper.h
index 26bbab2fab..12f8a0acea 100644
--- a/target/riscv/helper.h
+++ b/target/riscv/helper.h
@@ -106,6 +106,8 @@ DEF_HELPER_1(wfi, void, env)
DEF_HELPER_1(tlb_flush, void, env)
#endif
+DEF_HELPER_3(atomic_check, void, env, tl, int)
+
/* Hypervisor functions */
#ifndef CONFIG_USER_ONLY
DEF_HELPER_1(hyp_tlb_flush, void, env)
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 1c60fb2e80..294687f001 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -1139,7 +1139,7 @@ void riscv_cpu_do_transaction_failed(CPUState *cs, hwaddr
physaddr,
RISCVCPU *cpu = RISCV_CPU(cs);
CPURISCVState *env = &cpu->env;
- if (access_type == MMU_DATA_STORE) {
+ if (access_type == MMU_DATA_STORE || env->amo_store_fault) {
cs->exception_index = RISCV_EXCP_STORE_AMO_ACCESS_FAULT;
} else if (access_type == MMU_DATA_LOAD) {
cs->exception_index = RISCV_EXCP_LOAD_ACCESS_FAULT;
diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 1a75ba11e6..d0343b15f8 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -114,6 +114,20 @@ target_ulong helper_csrrw_i128(CPURISCVState *env, int csr,
return int128_getlo(rv);
}
+void helper_atomic_check(CPURISCVState *env, target_ulong address,
+ int mmu_idx)
+{
+#ifndef CONFIG_USER_ONLY
+ void *phost;
+ int ret = probe_access_flags(env, address, MMU_DATA_STORE, mmu_idx, false,
+ &phost, GETPC());
+
+ if (ret & TLB_MMIO) {
+ env->amo_store_fault = true;
+ }
+#endif
+}
+
#ifndef CONFIG_USER_ONLY
target_ulong helper_sret(CPURISCVState *env)
diff --git a/target/riscv/insn_trans/trans_rva.c.inc
b/target/riscv/insn_trans/trans_rva.c.inc
index 45db82c9be..b3e05613d7 100644
--- a/target/riscv/insn_trans/trans_rva.c.inc
+++ b/target/riscv/insn_trans/trans_rva.c.inc
@@ -83,6 +83,9 @@ static bool gen_amo(DisasContext *ctx, arg_atomic *a,
TCGv dest = dest_gpr(ctx, a->rd);
TCGv src1 = get_address(ctx, a->rs1, 0);
TCGv src2 = get_gpr(ctx, a->rs2, EXT_NONE);
+ TCGv_i32 mem_idx = tcg_constant_i32(ctx->mem_idx);
+
+ gen_helper_atomic_check(cpu_env, src1, mem_idx);
func(dest, src1, src2, ctx->mem_idx, mop);
--
2.35.1
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