lkml.org 
[lkml]   [2019]   [Jul]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v7 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL
On Mon, Jul 15, 2019 at 09:22:14AM +0800, Tao Xu wrote:
> On 7/12/2019 11:52 PM, Sean Christopherson wrote:
> >The SDM only defines bits 31:0, and the kernel uses a u32 to cache its
> >value. I assume bits 63:32 are reserved? I'm guessing we also need an
> >SDM update...
> >
>
> The SDM define IA32_UMWAIT_CONTROL is a 32bit MSR. So need me to set 63:32
> reserved?

Huh, I didn't realize the SDM allows 32 bit MSRs, I assumed all bits
needed to be explicitly defined even if the underlying implementation only
tracked 32 bits.

RDMSR:

If fewer than 64 bits are implemented in the MSR being read, the values
return in EDX:EAX in unimplemented bit locations are undefined.

WRMSR:

Undefined or reserved bits in an MSR should be set to values previously
read.

From KVM's perspective, bits 63:32 should be treated as reserved-to-zero.
This also means that struct vcpu_vmx can track a u32 instead of a u64
for msr_ia32_umwait_control.

\
 
 \ /
  Last update: 2019-07-15 17:45    [W:0.057 / U:9.932 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site