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Re: [Qemu-devel] [PATCH 1/2] mips: Improve segment defs for KVM T&E gues


From: Philippe Mathieu-Daudé
Subject: Re: [Qemu-devel] [PATCH 1/2] mips: Improve segment defs for KVM T&E guests
Date: Mon, 31 Jul 2017 15:17:48 -0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 07/31/2017 10:09 AM, James Hogan wrote:
Improve the segment definitions used by get_physical_address() to yield
target_ulong types, e.g. 0xffffffff80000000 instead of 0x80000000. This
is in preparation for enabling emulation of MIPS KVM T&E segments in TCG
MIPS targets, which unlike KVM could potentially have 64-bit
target_ulong. In such a case the offset guest KSEG0 address ends up at
e.g. 0x000000008xxxxxxx instead of 0xffffffff8xxxxxxx.

This also allows the casts to int32_t that force sign extension to be
removed, which removes any confusion due to relational comparison of
unsigned (target_ulong) and signed (int32_t) types.

Signed-off-by: James Hogan <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

Cc: Yongbok Kim <address@hidden>
Cc: Aurelien Jarno <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Cc: address@hidden
---
  target/mips/helper.c | 23 +++++++++++------------
  1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/target/mips/helper.c b/target/mips/helper.c
index a2b79e8725a6..05883b9f4251 100644
--- a/target/mips/helper.c
+++ b/target/mips/helper.c
@@ -216,14 +216,14 @@ static int get_physical_address (CPUMIPSState *env, 
hwaddr *physical,
      /* effective address (modified for KVM T&E kernel segments) */
      target_ulong address = real_address;
-#define USEG_LIMIT 0x7FFFFFFFUL
-#define KSEG0_BASE      0x80000000UL
-#define KSEG1_BASE      0xA0000000UL
-#define KSEG2_BASE      0xC0000000UL
-#define KSEG3_BASE      0xE0000000UL
+#define USEG_LIMIT      ((target_ulong)(int32_t)0x7FFFFFFFUL)
+#define KSEG0_BASE      ((target_ulong)(int32_t)0x80000000UL)
+#define KSEG1_BASE      ((target_ulong)(int32_t)0xA0000000UL)
+#define KSEG2_BASE      ((target_ulong)(int32_t)0xC0000000UL)
+#define KSEG3_BASE      ((target_ulong)(int32_t)0xE0000000UL)
-#define KVM_KSEG0_BASE 0x40000000UL
-#define KVM_KSEG2_BASE  0x60000000UL
+#define KVM_KSEG0_BASE  ((target_ulong)(int32_t)0x40000000UL)
+#define KVM_KSEG2_BASE  ((target_ulong)(int32_t)0x60000000UL)
if (kvm_enabled()) {
          /* KVM T&E adds guest kernel segments in useg */
@@ -307,17 +307,17 @@ static int get_physical_address (CPUMIPSState *env, 
hwaddr *physical,
              ret = TLBRET_BADADDR;
          }
  #endif
-    } else if (address < (int32_t)KSEG1_BASE) {
+    } else if (address < KSEG1_BASE) {
          /* kseg0 */
          ret = get_segctl_physical_address(env, physical, prot, real_address, 
rw,
                                            access_type, mmu_idx,
                                            env->CP0_SegCtl1 >> 16, 0x1FFFFFFF);
-    } else if (address < (int32_t)KSEG2_BASE) {
+    } else if (address < KSEG2_BASE) {
          /* kseg1 */
          ret = get_segctl_physical_address(env, physical, prot, real_address, 
rw,
                                            access_type, mmu_idx,
                                            env->CP0_SegCtl1, 0x1FFFFFFF);
-    } else if (address < (int32_t)KSEG3_BASE) {
+    } else if (address < KSEG3_BASE) {
          /* sseg (kseg2) */
          ret = get_segctl_physical_address(env, physical, prot, real_address, 
rw,
                                            access_type, mmu_idx,
@@ -974,8 +974,7 @@ void mips_cpu_do_interrupt(CPUState *cs)
          } else if (cause == 30 && !(env->CP0_Config3 & (1 << CP0C3_SC) &&
                                      env->CP0_Config5 & (1 << CP0C5_CV))) {
              /* Force KSeg1 for cache errors */
-            env->active_tc.PC = (int32_t)KSEG1_BASE |
-                                (env->CP0_EBase & 0x1FFFF000);
+            env->active_tc.PC = KSEG1_BASE | (env->CP0_EBase & 0x1FFFF000);
          } else {
              env->active_tc.PC = env->CP0_EBase & ~0xfff;
          }




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