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From: "Jan Beulich" <JBeulich@suse.com>
To: Euan Harris <euan.harris@citrix.com>
Cc: andrew.cooper3@citrix.com, kevin.tian@intel.com,
	jun.nakajima@intel.com, xen-devel@lists.xenproject.org
Subject: Re: [PATCH] nested vmx: Intercept guest rdmsr for MSR_IA32_VMX_VMFUNC
Date: Tue, 07 Jun 2016 04:35:28 -0600	[thread overview]
Message-ID: <5756BF9002000078000F2865@prv-mh.provo.novell.com> (raw)
In-Reply-To: <1465294718-31626-1-git-send-email-euan.harris@citrix.com>

>>> On 07.06.16 at 12:18, <euan.harris@citrix.com> wrote:
> Guest reads of MSR_IA32_VMX_VMFUNC should be handled by
> the logic in vmx_msr_read_intercept().   Otherwise a guest
> can read the raw host value of this MSR, even if nested
> vmx is disabled.
> 
> Signed-off-by: Euan Harris <euan.harris@citrix.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

Albeit ...

> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2624,7 +2624,7 @@ static int vmx_msr_read_intercept(unsigned int msr, uint64_t *msr_content)
>          __vmread(GUEST_IA32_DEBUGCTL, msr_content);
>          break;
>      case IA32_FEATURE_CONTROL_MSR:
> -    case MSR_IA32_VMX_BASIC...MSR_IA32_VMX_TRUE_ENTRY_CTLS:
> +    case MSR_IA32_VMX_BASIC...MSR_IA32_VMX_VMFUNC:
>          if ( !nvmx_msr_read_intercept(msr, msr_content) )
>              goto gp_fault;
>          break;

... retaining this code structure makes it likely that some future
addition will lead to the same problem again. I think there should
be something like MSR_IA32_VMX_LAST added to msr-index.h,
and get used here instead. Suitably placed it would make pretty
obvious to someone adding a new MSR there that this value also
needs updating.

Or alternatively: Is there an architectural upper bound to the
VMX MSR range? If so, we could widen the set to the full range
in one go.

VMX maintainers - I'd appreciate if you could take care of this in
one way or another.

Jan


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  reply	other threads:[~2016-06-07 10:35 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-07 10:18 Euan Harris
2016-06-07 10:35 ` Jan Beulich [this message]
2016-06-07 10:53   ` Euan Harris
2016-06-07 11:39     ` Andrew Cooper
2016-06-08  6:09 ` Tian, Kevin
2016-06-08 11:54 ` Wei Liu

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