MTRR support on x86 (Carl-Daniel Hailfinger)

The current codebase ignores MTRR (Memory Type Range Register)
configuration writes and reads because Qemu does not implement caching.
All BIOS/firmware in know of for x86 do implement a mode called
Cache-as-RAM (CAR) which locks down the CPU cache lines and uses the CPU
cache like RAM before RAM is enabled. Qemu assumes RAM is accessible
from the start, but it would be nice to be able to run real
BIOS/firmware in Qemu. For that, we need CAR support and for CAR support
we have to support MTRRs.

This patch is a first step in that direction. MTRRs are MSRs supported
by all recent x86 CPUs, even old i586. Besides influencing cache, the
MTRRs can be written and read back, so discarding MTRR writes violates
the expectations of existing code out there.

An added benefit of this patch is that it fixes the following Linux
kernel error message present in recent kernels (provided the BIOS has
the recent MTRR patches applied):
 ------------[ cut here ]------------
WARNING: at arch/x86/kernel/cpu/mtrr/main.c:1500 mtrr_trim_uncached_memory+0x382/0x384()
WARNING: strange, CPU MTRRs all blank?
Modules linked in:
Supported: Yes
Pid: 0, comm: swapper Not tainted 2.6.27.7-9-default #1
 [<c0106570>] dump_trace+0x6b/0x249
 [<c01070a5>] show_trace+0x20/0x39
 [<c0343c02>] dump_stack+0x71/0x76
 [<c012acb2>] warn_slowpath+0x6f/0x90
 [<c0542f8f>] mtrr_trim_uncached_memory+0x382/0x384
 [<c053f24d>] setup_arch+0x40d/0x639
 [<c053a6ac>] start_kernel+0x6b/0x31f
 =======================
 ---[ end trace 4eaa2a86a8e2da22 ]---

Handle common x86 MTRR reads and writes, but don't act on them.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6449 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 80 insertions, 0 deletions

diff --git a/target-i386/op_helper.c b/target-i386/op_helper.c
index dcbc361a02..1a615b3ba0 100644
--- a/target-i386/op_helper.c
+++ b/target-i386/op_helper.c
@@ -3050,6 +3050,46 @@ void helper_wrmsr(void)
         env->kernelgsbase = val;
         break;
 #endif
+    case MSR_MTRRphysBase(0):
+    case MSR_MTRRphysBase(1):
+    case MSR_MTRRphysBase(2):
+    case MSR_MTRRphysBase(3):
+    case MSR_MTRRphysBase(4):
+    case MSR_MTRRphysBase(5):
+    case MSR_MTRRphysBase(6):
+    case MSR_MTRRphysBase(7):
+        env->mtrr_var[((uint32_t)ECX - MSR_MTRRphysBase(0)) / 2].base = val;
+        break;
+    case MSR_MTRRphysMask(0):
+    case MSR_MTRRphysMask(1):
+    case MSR_MTRRphysMask(2):
+    case MSR_MTRRphysMask(3):
+    case MSR_MTRRphysMask(4):
+    case MSR_MTRRphysMask(5):
+    case MSR_MTRRphysMask(6):
+    case MSR_MTRRphysMask(7):
+        env->mtrr_var[((uint32_t)ECX - MSR_MTRRphysMask(0)) / 2].mask = val;
+        break;
+    case MSR_MTRRfix64K_00000:
+        env->mtrr_fixed[(uint32_t)ECX - MSR_MTRRfix64K_00000] = val;
+        break;
+    case MSR_MTRRfix16K_80000:
+    case MSR_MTRRfix16K_A0000:
+        env->mtrr_fixed[(uint32_t)ECX - MSR_MTRRfix16K_80000 + 1] = val;
+        break;
+    case MSR_MTRRfix4K_C0000:
+    case MSR_MTRRfix4K_C8000:
+    case MSR_MTRRfix4K_D0000:
+    case MSR_MTRRfix4K_D8000:
+    case MSR_MTRRfix4K_E0000:
+    case MSR_MTRRfix4K_E8000:
+    case MSR_MTRRfix4K_F0000:
+    case MSR_MTRRfix4K_F8000:
+        env->mtrr_fixed[(uint32_t)ECX - MSR_MTRRfix4K_C0000 + 3] = val;
+        break;
+    case MSR_MTRRdefType:
+        env->mtrr_deftype = val;
+        break;
     default:
         /* XXX: exception ? */
         break;
@@ -3122,6 +3162,46 @@ void helper_rdmsr(void)
         }
         break;
 #endif
+    case MSR_MTRRphysBase(0):
+    case MSR_MTRRphysBase(1):
+    case MSR_MTRRphysBase(2):
+    case MSR_MTRRphysBase(3):
+    case MSR_MTRRphysBase(4):
+    case MSR_MTRRphysBase(5):
+    case MSR_MTRRphysBase(6):
+    case MSR_MTRRphysBase(7):
+        val = env->mtrr_var[((uint32_t)ECX - MSR_MTRRphysBase(0)) / 2].base;
+        break;
+    case MSR_MTRRphysMask(0):
+    case MSR_MTRRphysMask(1):
+    case MSR_MTRRphysMask(2):
+    case MSR_MTRRphysMask(3):
+    case MSR_MTRRphysMask(4):
+    case MSR_MTRRphysMask(5):
+    case MSR_MTRRphysMask(6):
+    case MSR_MTRRphysMask(7):
+        val = env->mtrr_var[((uint32_t)ECX - MSR_MTRRphysMask(0)) / 2].mask;
+        break;
+    case MSR_MTRRfix64K_00000:
+        val = env->mtrr_fixed[0];
+        break;
+    case MSR_MTRRfix16K_80000:
+    case MSR_MTRRfix16K_A0000:
+        val = env->mtrr_fixed[(uint32_t)ECX - MSR_MTRRfix16K_80000 + 1];
+        break;
+    case MSR_MTRRfix4K_C0000:
+    case MSR_MTRRfix4K_C8000:
+    case MSR_MTRRfix4K_D0000:
+    case MSR_MTRRfix4K_D8000:
+    case MSR_MTRRfix4K_E0000:
+    case MSR_MTRRfix4K_E8000:
+    case MSR_MTRRfix4K_F0000:
+    case MSR_MTRRfix4K_F8000:
+        val = env->mtrr_fixed[(uint32_t)ECX - MSR_MTRRfix4K_C0000 + 3];
+        break;
+    case MSR_MTRRdefType:
+        val = env->mtrr_deftype;
+        break;
     default:
         /* XXX: exception ? */
         val = 0;