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[Qemu-devel] [PATCH v4 17/26] RISC-V: Hardwire satp to 0 for no-mmu case
From: |
Michael Clark |
Subject: |
[Qemu-devel] [PATCH v4 17/26] RISC-V: Hardwire satp to 0 for no-mmu case |
Date: |
Mon, 19 Mar 2018 14:18:40 -0700 |
satp is WARL so it should not trap on illegal writes, rather
it can be hardwired to zero and silently ignore illegal writes.
It seems the RISC-V WARL behaviour is preferred to having to
trap overhead versus simply reading back the value and checking
if the write took (saves hundreds of cycles and more complex
trap handling code).
Cc: Sagar Karandikar <address@hidden>
Cc: Bastian Koppelmann <address@hidden>
Signed-off-by: Michael Clark <address@hidden>
Signed-off-by: Palmer Dabbelt <address@hidden>
---
target/riscv/op_helper.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index e34715d..dd3e417 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -242,7 +242,7 @@ void csr_write_helper(CPURISCVState *env, target_ulong
val_to_write,
}
case CSR_SATP: /* CSR_SPTBR */ {
if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
- goto do_illegal;
+ break;
}
if (env->priv_ver <= PRIV_VERSION_1_09_1 && (val_to_write ^
env->sptbr))
{
@@ -452,7 +452,10 @@ target_ulong csr_read_helper(CPURISCVState *env,
target_ulong csrno)
return env->scounteren;
case CSR_SCAUSE:
return env->scause;
- case CSR_SPTBR:
+ case CSR_SATP: /* CSR_SPTBR */
+ if (!riscv_feature(env, RISCV_FEATURE_MMU)) {
+ return 0;
+ }
if (env->priv_ver >= PRIV_VERSION_1_10_0) {
return env->satp;
} else {
--
2.7.0
- [Qemu-devel] [PATCH v4 08/26] RISC-V: Make sure rom has space for fdt, (continued)
- [Qemu-devel] [PATCH v4 08/26] RISC-V: Make sure rom has space for fdt, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 02/26] RISC-V: Replace hardcoded constants with enum values, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 03/26] RISC-V: Make virt board description match spike, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 10/26] RISC-V: Hold rcu_read_lock when accessing memory, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 09/26] RISC-V: Include intruction hex in disassembly, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 07/26] RISC-V: Remove unused class definitions, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 12/26] RISC-V: Update E order and I extension order, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 13/26] RISC-V: Make some header guards more specific, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 16/26] RISC-V: Remove EM_RISCV ELF_MACHINE indirection, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 11/26] RISC-V: Improve page table walker spec compliance, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 17/26] RISC-V: Hardwire satp to 0 for no-mmu case,
Michael Clark <=
- [Qemu-devel] [PATCH v4 14/26] RISC-V: Make virt header comment title consistent, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 24/26] RISC-V: Clear mtval/stval on exceptions without info, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 21/26] RISC-V: No traps on writes to misa, minstret, mcycle, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 20/26] RISC-V: vectored traps are optional, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 15/26] RISC-V: Use memory_region_is_ram in pte update, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 22/26] RISC-V: Remove support for adhoc X_COP interrupt, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 23/26] RISC-V: Convert cpu definition towards future model, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 25/26] RISC-V: Remove erroneous comment from translate.c, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 19/26] RISC-V: riscv-qemu port supports sv39 and sv48, Michael Clark, 2018/03/19
- [Qemu-devel] [PATCH v4 18/26] RISC-V: Remove braces from satp case statement, Michael Clark, 2018/03/19