Patchwork [Bug,657329,NEW] APIC unusable on QEMU

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Submitter Geoffrey Lee
Date Oct. 9, 2010, 1:51 p.m.
Message ID <20101009135148.4804.78327.malonedeb@palladium.canonical.com>
Download mbox | patch
Permalink /patch/67321/
State New
Headers show

Comments

Geoffrey Lee - Oct. 9, 2010, 1:51 p.m.
Public bug reported:

The APIC is unusable with QEMU using x86-64 system emulation.  Problem
exists in the latest stable QEMU 0.12.5 as well as the latest git head.
I am using Mac OS X 10.6, 64-bit version of QEMU.

The QEMU binary was configured with:

 ./configure --target-list=i386-softmmu,x86_64-softmmubck-i-search:
conf_

Problem is that the hw/apic.c file (as well as a few other naughty
files) rely on the cpu_single_env global - which is set to NULL in cpu-
exec.c.

Below is a test reading the local APIC version register:

Before taking it out:

(qemu) xp 0xfee00030
00000000fee00030: 0x00000000
(qemu)

After:

(qemu) xp 0xfee00030
00000000fee00030: 0x00050011
(qemu)

Quick fix below.  I don't know if there are any side effects with this,
if this is OK maybe we can fix it like this for the stable versions and
fix the HEAD to not rely on the cpu_single_env global.
Jan Kiszka - Oct. 9, 2010, 2:44 p.m.
Am 09.10.2010 15:51, Geoffrey Lee wrote:
> Public bug reported:
> 
> The APIC is unusable with QEMU using x86-64 system emulation.  Problem
> exists in the latest stable QEMU 0.12.5 as well as the latest git head.
> I am using Mac OS X 10.6, 64-bit version of QEMU.
> 
> The QEMU binary was configured with:
> 
>  ./configure --target-list=i386-softmmu,x86_64-softmmubck-i-search:
> conf_
> 
> Problem is that the hw/apic.c file (as well as a few other naughty
> files) rely on the cpu_single_env global - which is set to NULL in cpu-
> exec.c.
> 
> Below is a test reading the local APIC version register:
> 
> Before taking it out:
> 
> (qemu) xp 0xfee00030
> 00000000fee00030: 0x00000000
> (qemu)
> 
> After:
> 
> (qemu) xp 0xfee00030
> 00000000fee00030: 0x00050011
> (qemu)

Well, the APIC is very well usable for the VCPUs (which run with proper
cpu_single_env set. It is just out of reach for your debugging attempt.
We are working (granted: not actively ATM) on a proper device dump
interface that will allow to inspect the current APIC state as well.

BTW, your "fix" won't work if you enable io-thread support.

Jan

Patch

diff --git a/cpu-exec.c b/cpu-exec.c
index dbdfdcc..3e966d7 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -674,7 +674,17 @@  int cpu_exec(CPUState *env1)
     env = (void *) saved_env_reg;
 
     /* fail safe : never use cpu_single_env outside cpu_exec() */
+#warning fixup devices which rely on this
+#if 0
+    /*
+     * Hello.  This is wrapped around an #if 0 ... #endif because that's
+     * what should happen.  However, certain naughty devices (like the APIC
+     * for instance, and a few others), access this global variable.
+     *
+     * So this is here for now ... until we fix up those devices.
+     */
     cpu_single_env = NULL;
+#endif
     return ret;
 }

** Affects: qemu
     Importance: Undecided
         Status: New

-- 
APIC unusable on QEMU
https://bugs.launchpad.net/bugs/657329
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Status in QEMU: New

Bug description:
The APIC is unusable with QEMU using x86-64 system emulation.  Problem exists in the latest stable QEMU 0.12.5 as well as the latest git head.  I am using Mac OS X 10.6, 64-bit version of QEMU.

The QEMU binary was configured with:

 ./configure --target-list=i386-softmmu,x86_64-softmmubck-i-search: conf_      

Problem is that the hw/apic.c file (as well as a few other naughty files) rely on the cpu_single_env global - which is set to NULL in cpu-exec.c.

Below is a test reading the local APIC version register:

Before taking it out:

(qemu) xp 0xfee00030
00000000fee00030: 0x00000000
(qemu)

After:

(qemu) xp 0xfee00030
00000000fee00030: 0x00050011
(qemu)

Quick fix below.  I don't know if there are any side effects with this, if this is OK maybe we can fix it like this for the stable versions and fix the HEAD to not rely on the cpu_single_env global.

diff --git a/cpu-exec.c b/cpu-exec.c
index dbdfdcc..3e966d7 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -674,7 +674,17 @@  int cpu_exec(CPUState *env1)
     env = (void *) saved_env_reg;
 
     /* fail safe : never use cpu_single_env outside cpu_exec() */
+#warning fixup devices which rely on this
+#if 0
+    /*
+     * Hello.  This is wrapped around an #if 0 ... #endif because that's
+     * what should happen.  However, certain naughty devices (like the APIC
+     * for instance, and a few others), access this global variable.
+     *
+     * So this is here for now ... until we fix up those devices.
+     */
     cpu_single_env = NULL;
+#endif
     return ret;
 }