Re: [ANNOUNCE] kvm-20 release

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

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Christian Hesse wrote:
> On Tuesday 24 April 2007, Avi Kivity wrote:
>   
>> Jeff Chua wrote:
>>     
>>> On 4/22/07, Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
>>>       
>>>> Significant cpu performance improvements (esp. for 32-bit guests on
>>>> 64-bit hosts), as well as Windows 2000 support (without acpi).
>>>>         
>>> Avi,
>>>
>>> Ecountered the following error with kvm-20 (external modules) on
>>> Linux-2.6.21-rc7.
>>>
>>> kvm_run: failed entry, reason 7
>>> kvm_run returned -8
>>>
>>> Runs fine with kvm-19 (external modules).
>>>
>>> Am I missing something?
>>>       
>> I'm missing something:
>>
>> - what host cpu?
>>
>> - what host bitness?
>>
>> - what guest OS?
>>     
>
> Hi Avi,
>
> same here, so I will answer in place:
>
> Samsung X11 with Intel Core Duo T2300 with Gentoo Linux and Kernel 2.6.21-rc7 
> + kvm-20. Guest OS is Win XP.
>
> Additionally I've patched my kernel with cfs v5 now. I thought that could be 
> the problem... Jeff, are you running cfs or any non mainline scheduler as 
> well?
>   

It may be the cpuid strangeness that Rusty saw.  Can you try the
attached patch?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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[-- Type: text/x-patch, Size: 3015 bytes --]

diff --git a/qemu/qemu-kvm.c b/qemu/qemu-kvm.c
index e00b0f3..46b0b99 100644
--- a/qemu/qemu-kvm.c
+++ b/qemu/qemu-kvm.c
@@ -682,6 +682,49 @@ void kvm_qemu_destroy(void)
     kvm_finalize(kvm_context);
 }
 
+static void host_cpuid(uint32_t function, uint32_t *eax, uint32_t *ebx,
+		       uint32_t *ecx, uint32_t *edx)
+{
+    uint32_t vec[4];
+
+    vec[0] = function;
+    asm volatile (
+#ifdef __x86_64__
+         "push %0;  push %%rsi \n\t"
+	 "push %%rax; push %%rbx; push %%rcx; push %%rdx \n\t"
+	 "mov 8*5(%%rsp), %%rsi \n\t"
+	 "mov (%%rsi), %%eax \n\t"
+	 "cpuid \n\t"
+	 "mov %%eax, (%%rsi) \n\t"
+	 "mov %%ebx, 4(%%rsi) \n\t"
+	 "mov %%ecx, 8(%%rsi) \n\t"
+	 "mov %%edx, 12(%%rsi) \n\t"
+	 "pop %%rdx; pop %%rcx; pop %%rbx; pop %%rax \n\t"
+	 "pop %%rsi; pop %0 \n\t"
+#else
+         "push %0;  push %%esi \n\t"
+	 "push %%eax; push %%ebx; push %%ecx; push %%edx \n\t"
+	 "mov 4*5(%%esp), %%esi \n\t"
+	 "mov (%%esi), %%eax \n\t"
+	 "cpuid \n\t"
+	 "mov %%eax, (%%esi) \n\t"
+	 "mov %%ebx, 4(%%esi) \n\t"
+	 "mov %%ecx, 8(%%esi) \n\t"
+	 "mov %%edx, 12(%%esi) \n\t"
+	 "pop %%edx; pop %%ecx; pop %%ebx; pop %%eax \n\t"
+	 "pop %%esi; pop %0 \n\t"
+#endif
+	 : : "rm"(vec) : "memory");
+    if (eax)
+	*eax = vec[0];
+    if (ebx)
+	*ebx = vec[1];
+    if (ecx)
+	*ecx = vec[2];
+    if (edx)
+	*edx = vec[3];
+}
+
 static void do_cpuid_ent(struct kvm_cpuid_entry *e, uint32_t function)
 {
     EAX = function;
@@ -694,17 +737,9 @@ static void do_cpuid_ent(struct kvm_cpuid_entry *e, uint32_t function)
     if (function == 1)
 	e->edx &= ~(1 << 12); /* disable mtrr support */
     if (function == 0x80000001) {
-	unsigned long h_eax = function, h_edx;
+	uint32_t h_eax, h_edx;
 
-
-	// push/pop hack to workaround gcc 3 register pressure trouble
-	asm (
-#ifdef __x86_64__
-	     "push %%rbx; push %%rcx; cpuid; pop %%rcx; pop %%rbx"
-#else
-	     "push %%ebx; push %%ecx; cpuid; pop %%ecx; pop %%ebx"
-#endif
-	     : "+a"(h_eax), "=d"(h_edx));
+	host_cpuid(function, &h_eax, NULL, NULL, &h_edx);
 
 	// long mode
 	if ((h_edx & 0x20000000) == 0)
@@ -722,27 +757,8 @@ static void do_cpuid_ent(struct kvm_cpuid_entry *e, uint32_t function)
     // is you use compatibility mode.
     if (function == 0) {
 	uint32_t bcd[3];
-	asm (
-#ifdef __x86_64__
-	     "push %%rax; push %%rbx; push %%rcx; push %%rdx \n\t"
-	     "mov $0, %%eax \n\t"
-	     "cpuid \n\t"
-	     "mov (%%rsp), %%rax \n\t"
-	     "mov %%ebx, (%%rax) \n\t"
-	     "mov %%ecx, 4(%%rax) \n\t"
-	     "mov %%edx, 8(%%rax) \n\t"
-	     "pop %%rdx; pop %%rcx; pop %%rbx; pop %%rax"
-#else
-	     "push %%eax; push %%ebx; push %%ecx; push %%edx \n\t"
-	     "mov $0, %%eax \n\t"
-	     "cpuid \n\t"
-	     "mov (%%esp), %%eax \n\t"
-	     "mov %%ebx, (%%eax) \n\t"
-	     "mov %%ecx, 4(%%eax) \n\t"
-	     "mov %%edx, 8(%%eax) \n\t"
-	     "pop %%edx; pop %%ecx; pop %%ebx; pop %%eax"
-#endif
-	     : : "d"(bcd) : "memory");
+
+	host_cpuid(0, NULL, &bcd[0], &bcd[1], &bcd[2]);
 	e->ebx = bcd[0];
 	e->ecx = bcd[1];
 	e->edx = bcd[2];

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