New: nVMX: TRUE* MSRs unnecessary
https://bugzilla.kernel.org/show_bug.cgi?id=54471
Summary: nVMX: TRUE* MSRs unnecessary
Product: Virtualization
Version: unspecified
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: enhancement
Priority: P1
Component: kvm
AssignedTo: [email protected]
ReportedBy: [email protected]
Regression: No
According to the spec, the TRUE* MSRs are only necessary if bit 55 of VMX_BASIC is on. Since we don't set this bit, we don't need to provide these MSRs... So probably we shouldn't.
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[Bug 54471] nVMX: TRUE* MSRs unnecessary
https://bugzilla.kernel.org/show_bug.cgi?id=54471
Nadav Har'El <[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |53601
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[Bug 54471] nVMX: TRUE* MSRs unnecessary
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=54471
--- Comment #1 from Anonymous Emailer <[email protected]> 2013-02-25 14:29:08 ---
Reply-To: [email protected]
Quoted 17 lines · On 2013-02-25 15:04, [email protected] wrote:
https://bugzilla.kernel.org/show_bug.cgi?id=54471
Summary: nVMX: TRUE* MSRs unnecessary
Product: Virtualization
Version: unspecified
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: enhancement
Priority: P1
Component: kvm
AssignedTo: [email protected]
ReportedBy: [email protected]
Regression: No
Quoted 3 lines
According to the spec, the TRUE* MSRs are only necessary if bit 55 of
VMX_BASICis on. Since we don't set this bit, we don't need to provide these MSRs... So probably we shouldn't.
I tend to say we should (i.e. set bit 55) as there is the risk that buggy guests could needlessly get confused when we expose very recent features (like EPT) and do not provide such "old-fashioned" stuff.
Jan
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Quoted 17 lines · On 2013-02-25 15:04, [email protected] wrote:
https://bugzilla.kernel.org/show_bug.cgi?id=54471
Summary: nVMX: TRUE* MSRs unnecessary
Product: Virtualization
Version: unspecified
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: enhancement
Priority: P1
Component: kvm
AssignedTo: [email protected]
ReportedBy: [email protected]
Regression: No
Quoted 3 lines
According to the spec, the TRUE* MSRs are only necessary if bit 55 of
VMX_BASICis on. Since we don't set this bit, we don't need to provide these MSRs... So probably we shouldn't.
I tend to say we should (i.e. set bit 55) as there is the risk that buggy guests could needlessly get confused when we expose very recent features (like EPT) and do not provide such "old-fashioned" stuff.
Jan
Signature · 2 lines
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux
[Bug 54471] nVMX: TRUE* MSRs unnecessary
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=54471
Bandan Das <[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |94971
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[Bug 54471] nVMX: TRUE* MSRs unnecessary
In reply to [email protected]https://bugzilla.kernel.org/show_bug.cgi?id=54471
Paolo Bonzini <[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |[email protected]
Kernel Version| |3.19
Resolution|--- |INVALID--- Comment #2 from Paolo Bonzini <[email protected]> ---
TRUE_* is needed to tell the guest that it can disable CR3 load/store exits. We were enabling this control by exposing a broken MSR_IA32_VMX_PROCBASED_CTLS value, but commit 560b7ee12ca5 (KVM: nVMX: Fix returned value of MSR_IA32_VMX_PROCBASED_CTLS, 2014-06-16). So we can no longer remove the TRUE_* MSRs.
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