Re: [Xen-devel] [PATCH RFC V2 4/6] xen: Support for VMCALL mem_events

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 07/11/2014 08:23 PM, Andrew Cooper wrote:
> On 11/07/14 16:43, Razvan Cojocaru wrote:
>> diff --git a/xen/include/public/hvm/params.h 
>> b/xen/include/public/hvm/params.h
>> index 614ff5f..d8f89b5 100644
>> --- a/xen/include/public/hvm/params.h
>> +++ b/xen/include/public/hvm/params.h
>> @@ -151,6 +151,8 @@
>>  /* Location of the VM Generation ID in guest physical address space. */
>>  #define HVM_PARAM_VM_GENERATION_ID_ADDR 34
>>  
>> -#define HVM_NR_PARAMS          35
>> +#define HVM_PARAM_MEMORY_EVENT_VMCALL 35
> 
> What is this hvmparam actually used for?  This patch only reads it, and
> as indicated previously, it is readwrite to the guest which likely
> breaks any assumptions you have about the trustworthness of the value
> found there.

I'm now using it to make sure that enabling it will not honour
HVMPME_onchangeonly:

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 89a0382..6e86d7c 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -5564,6 +5564,7 @@ long do_hvm_op(unsigned long op,
XEN_GUEST_HANDLE_PARAM(void) arg)
             case HVM_PARAM_MEMORY_EVENT_INT3:
             case HVM_PARAM_MEMORY_EVENT_SINGLE_STEP:
             case HVM_PARAM_MEMORY_EVENT_MSR:
+            case HVM_PARAM_MEMORY_EVENT_VMCALL:
                 if ( d == current->domain )
                 {
                     rc = -EPERM;


Thanks,
Razvan Cojocaru

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