Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)

2007-12-03 Thread Avi Kivity
Amit Shah wrote:
 * Anthony Liguori wrote:
   
 Amit Shah wrote:
 
 * Anthony Liguori wrote:
  

   
 This patch refactors the current hypercall infrastructure to better
 support live migration and SMP.  It eliminates the hypercall page by
 trapping the UD exception that would occur if you used the wrong
 hypercall instruction for the underlying architecture and replacing it
 with the right one lazily. 
 
 This doesn't work right for SVM. It keeps looping indefinitely; on a
 kvm_stat run, I get about 230,000 light vm exits per second, with the
 hypercall never returning to the guest.

 ...
  
   
 What are you using to issue the hypercall?
 

 +   r = kvm_hypercall1(KVM_PV_PCI_DEVICE, page_gfn);

 Setup is done by:

 +   if (!kvm_para_available()) {
 +   printk(KERN_ERR KVM paravirt support not available\n);
 +   r = -ENODEV;
 +   goto out_dereg;
 +   }
   

There was a bug where instructions with a modrm byte specifying a 
register would try to access memory.  In the memory was not mapped,  
emulation would fail. vmcall is one such instruction.  This was fixed by

commit f83562246921d6a8a7de8b76853a6835ace3699d
Author: Aurelien Jarno [EMAIL PROTECTED]
Date:   Wed Oct 17 19:30:41 2007 +0200

KVM: x86 emulator: fix access registers for instructions with ModR/M 
byte and Mod = 3

The patch belows changes the access type to register from memory for
instructions that are declared as SrcMem or DstMem, but have a
ModR/M byte with Mod = 3.

It fixes (at least) the lmsw and smsw instructions on an AMD64 CPU,
which are needed for FreeBSD.

Signed-off-by: Aurelien Jarno [EMAIL PROTECTED]
Signed-off-by: Avi Kivity [EMAIL PROTECTED]

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 7c95ae5..8c50496 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -835,6 +835,14 @@ modrm_done:
if (c-twobyte  c-b == 0x01
 c-modrm_reg == 7)
break;
+   /*
+* For instructions with a ModR/M byte, switch to register
+* access if Mod = 3.
+*/
+   if ((c-d  ModRM)  c-modrm_mod == 3) {
+   c-src.type = OP_REG;
+   break;
+   }
 srcmem_common:
c-src.type = OP_MEM;
break;
@@ -897,7 +905,14 @@ srcmem_common:
}
break;
case DstMem:
-   c-dst.type = OP_MEM;
+   /*
+* For instructions with a ModR/M byte, switch to register
+* access if Mod = 3.
+*/
+   if ((c-d  ModRM)  c-modrm_mod == 3)
+   c-dst.type = OP_REG;
+   else
+   c-dst.type = OP_MEM;
break;
}




-- 
error compiling committee.c: too many arguments to function


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Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)

2007-12-03 Thread Amit Shah
* Anthony Liguori wrote:
 Amit Shah wrote:
  * Anthony Liguori wrote:
   
 
  This patch refactors the current hypercall infrastructure to better
  support live migration and SMP.  It eliminates the hypercall page by
  trapping the UD exception that would occur if you used the wrong
  hypercall instruction for the underlying architecture and replacing it
  with the right one lazily. 
 
  This doesn't work right for SVM. It keeps looping indefinitely; on a
  kvm_stat run, I get about 230,000 light vm exits per second, with the
  hypercall never returning to the guest.
 
  ...
   

 What are you using to issue the hypercall?

+   r = kvm_hypercall1(KVM_PV_PCI_DEVICE, page_gfn);

Setup is done by:

+   if (!kvm_para_available()) {
+   printk(KERN_ERR KVM paravirt support not available\n);
+   r = -ENODEV;
+   goto out_dereg;
+   }

I also couldn't get the has_feature to work properly.

See:

http://lkml.org/lkml/2007/11/7/129

I had to change the hypercall address to 0f 01 d9 for it to get working.


 Regards,

 Anthony Liguori



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Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)

2007-12-03 Thread Amit Shah
* Avi Kivity wrote:
 Amit Shah wrote:
  * Anthony Liguori wrote:
   
 
  Amit Shah wrote:
     
 
  What are you using to issue the hypercall?
     
 
  +       r = kvm_hypercall1(KVM_PV_PCI_DEVICE, page_gfn);
 
  Setup is done by:
 
  +       if (!kvm_para_available()) {
  +               printk(KERN_ERR KVM paravirt support not available\n);
  +               r = -ENODEV;
  +               goto out_dereg;
  +       }
   

 There was a bug where instructions with a modrm byte specifying a
 register would try to access memory.  In the memory was not mapped,  
 emulation would fail. vmcall is one such instruction.  This was fixed by

 commit f83562246921d6a8a7de8b76853a6835ace3699d
 Author: Aurelien Jarno [EMAIL PROTECTED]
 Date:   Wed Oct 17 19:30:41 2007 +0200

     KVM: x86 emulator: fix access registers for instructions with ModR/M
 byte and Mod = 3

Thanks, and thank you, Aurelien!

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Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)

2007-12-02 Thread Amit Shah
* Anthony Liguori wrote:
 This patch refactors the current hypercall infrastructure to better support
 live migration and SMP.  It eliminates the hypercall page by trapping the
 UD exception that would occur if you used the wrong hypercall instruction
 for the underlying architecture and replacing it with the right one lazily.

This doesn't work right for SVM. It keeps looping indefinitely; on a kvm_stat 
run, I get about 230,000 light vm exits per second, with the hypercall never 
returning to the guest.

...

 diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
 index 729f1cd..d09a9f5 100644
 --- a/drivers/kvm/svm.c
 +++ b/drivers/kvm/svm.c
 @@ -476,7 +476,8 @@ static void init_vmcb(struct vmcb *vmcb)
   INTERCEPT_DR5_MASK |
   INTERCEPT_DR7_MASK;

 - control-intercept_exceptions = 1  PF_VECTOR;
 + control-intercept_exceptions = (1  PF_VECTOR) |
 + (1  UD_VECTOR);


   control-intercept =(1ULL  INTERCEPT_INTR) |
 @@ -970,6 +971,17 @@ static int pf_interception(struct vcpu_svm *svm,
 struct kvm_run *kvm_run) return 0;
  }

 +static int ud_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
 +{
 + int er;
 +
 + er = emulate_instruction(svm-vcpu, kvm_run, 0, 0);
 + if (er != EMULATE_DONE)
 + inject_ud(svm-vcpu);
 +
 + return 1;
 +}
 +
  static int nm_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
  {
   svm-vmcb-control.intercept_exceptions = ~(1  NM_VECTOR);
 @@ -1036,7 +1048,8 @@ static int vmmcall_interception(struct vcpu_svm *svm,
 struct kvm_run *kvm_run) {
   svm-next_rip = svm-vmcb-save.rip + 3;
   skip_emulated_instruction(svm-vcpu);
 - return kvm_hypercall(svm-vcpu, kvm_run);
 + kvm_emulate_hypercall(svm-vcpu);
 + return 1;
  }

  static int invalid_op_interception(struct vcpu_svm *svm,
 @@ -1232,6 +1245,7 @@ static int (*svm_exit_handlers[])(struct vcpu_svm
 *svm, [SVM_EXIT_WRITE_DR3]= emulate_on_interception,
   [SVM_EXIT_WRITE_DR5]= emulate_on_interception,
   [SVM_EXIT_WRITE_DR7]= emulate_on_interception,
 + [SVM_EXIT_EXCP_BASE + UD_VECTOR]= ud_interception,
   [SVM_EXIT_EXCP_BASE + PF_VECTOR]= pf_interception,
   [SVM_EXIT_EXCP_BASE + NM_VECTOR]= nm_interception,
   [SVM_EXIT_INTR] = nop_on_interception,
 @@ -1664,7 +1678,6 @@ svm_patch_hypercall(struct kvm_vcpu *vcpu, unsigned
 char *hypercall) hypercall[0] = 0x0f;
   hypercall[1] = 0x01;
   hypercall[2] = 0xd9;
 - hypercall[3] = 0xc3;
  }

...

 +/* This instruction is vmcall.  On non-VT architectures, it will generate
 a + * trap that we will then rewrite to the appropriate instruction. */
 -#define __NR_hypercalls  0
 +#define KVM_HYPERCALL .byte 0x0f,0x01,0xc1

.. which never happens.

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Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)

2007-12-02 Thread Avi Kivity
Amit Shah wrote:
 * Anthony Liguori wrote:
   
 This patch refactors the current hypercall infrastructure to better support
 live migration and SMP.  It eliminates the hypercall page by trapping the
 UD exception that would occur if you used the wrong hypercall instruction
 for the underlying architecture and replacing it with the right one lazily.
 

 This doesn't work right for SVM. It keeps looping indefinitely; on a kvm_stat 
 run, I get about 230,000 light vm exits per second, with the hypercall never 
 returning to the guest.
   

I just tested kvm.git with (the new) hypercall.flat testcase.  Seems to 
work fine.

-- 
error compiling committee.c: too many arguments to function


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Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)

2007-12-02 Thread Anthony Liguori
Amit Shah wrote:
 * Anthony Liguori wrote:
   
 This patch refactors the current hypercall infrastructure to better support
 live migration and SMP.  It eliminates the hypercall page by trapping the
 UD exception that would occur if you used the wrong hypercall instruction
 for the underlying architecture and replacing it with the right one lazily.
 

 This doesn't work right for SVM. It keeps looping indefinitely; on a kvm_stat 
 run, I get about 230,000 light vm exits per second, with the hypercall never 
 returning to the guest.

 ...
   

What are you using to issue the hypercall?

Regards,

Anthony Liguori

 diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
 index 729f1cd..d09a9f5 100644
 --- a/drivers/kvm/svm.c
 +++ b/drivers/kvm/svm.c
 @@ -476,7 +476,8 @@ static void init_vmcb(struct vmcb *vmcb)
  INTERCEPT_DR5_MASK |
  INTERCEPT_DR7_MASK;

 -control-intercept_exceptions = 1  PF_VECTOR;
 +control-intercept_exceptions = (1  PF_VECTOR) |
 +(1  UD_VECTOR);


  control-intercept =(1ULL  INTERCEPT_INTR) |
 @@ -970,6 +971,17 @@ static int pf_interception(struct vcpu_svm *svm,
 struct kvm_run *kvm_run) return 0;
  }

 +static int ud_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
 +{
 +int er;
 +
 +er = emulate_instruction(svm-vcpu, kvm_run, 0, 0);
 +if (er != EMULATE_DONE)
 +inject_ud(svm-vcpu);
 +
 +return 1;
 +}
 +
  static int nm_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
  {
  svm-vmcb-control.intercept_exceptions = ~(1  NM_VECTOR);
 @@ -1036,7 +1048,8 @@ static int vmmcall_interception(struct vcpu_svm *svm,
 struct kvm_run *kvm_run) {
  svm-next_rip = svm-vmcb-save.rip + 3;
  skip_emulated_instruction(svm-vcpu);
 -return kvm_hypercall(svm-vcpu, kvm_run);
 +kvm_emulate_hypercall(svm-vcpu);
 +return 1;
  }

  static int invalid_op_interception(struct vcpu_svm *svm,
 @@ -1232,6 +1245,7 @@ static int (*svm_exit_handlers[])(struct vcpu_svm
 *svm, [SVM_EXIT_WRITE_DR3]   = emulate_on_interception,
  [SVM_EXIT_WRITE_DR5]= emulate_on_interception,
  [SVM_EXIT_WRITE_DR7]= emulate_on_interception,
 +[SVM_EXIT_EXCP_BASE + UD_VECTOR]= ud_interception,
  [SVM_EXIT_EXCP_BASE + PF_VECTOR]= pf_interception,
  [SVM_EXIT_EXCP_BASE + NM_VECTOR]= nm_interception,
  [SVM_EXIT_INTR] = nop_on_interception,
 @@ -1664,7 +1678,6 @@ svm_patch_hypercall(struct kvm_vcpu *vcpu, unsigned
 char *hypercall) hypercall[0] = 0x0f;
  hypercall[1] = 0x01;
  hypercall[2] = 0xd9;
 -hypercall[3] = 0xc3;
  }
 

 ...

   
 +/* This instruction is vmcall.  On non-VT architectures, it will generate
 a + * trap that we will then rewrite to the appropriate instruction. */
 -#define __NR_hypercalls 0
 +#define KVM_HYPERCALL .byte 0x0f,0x01,0xc1
 

 .. which never happens.
   


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