Re: [PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-29 Thread Jim Mattson
On Sun, Jan 28, 2018 at 4:58 PM, KarimAllah Ahmed wrote: > Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for > guests that will only mitigate Spectre V2 through IBRS+IBPB and will not > be using a retpoline+IBPB based approach. > > To avoid the overhead of

Re: [PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-29 Thread Jim Mattson
On Sun, Jan 28, 2018 at 4:58 PM, KarimAllah Ahmed wrote: > Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for > guests that will only mitigate Spectre V2 through IBRS+IBPB and will not > be using a retpoline+IBPB based approach. > > To avoid the overhead of atomically saving

Re: [PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-29 Thread KarimAllah Ahmed
On 01/29/2018 11:44 AM, Paolo Bonzini wrote: On 29/01/2018 01:58, KarimAllah Ahmed wrote: Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for guests that will only mitigate Spectre V2 through IBRS+IBPB and will not be using a retpoline+IBPB based approach. To avoid the

Re: [PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-29 Thread KarimAllah Ahmed
On 01/29/2018 11:44 AM, Paolo Bonzini wrote: On 29/01/2018 01:58, KarimAllah Ahmed wrote: Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for guests that will only mitigate Spectre V2 through IBRS+IBPB and will not be using a retpoline+IBPB based approach. To avoid the

Re: [PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-29 Thread Paolo Bonzini
On 29/01/2018 01:58, KarimAllah Ahmed wrote: > Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for > guests that will only mitigate Spectre V2 through IBRS+IBPB and will not > be using a retpoline+IBPB based approach. > > To avoid the overhead of atomically saving and restoring

Re: [PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-29 Thread Paolo Bonzini
On 29/01/2018 01:58, KarimAllah Ahmed wrote: > Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for > guests that will only mitigate Spectre V2 through IBRS+IBPB and will not > be using a retpoline+IBPB based approach. > > To avoid the overhead of atomically saving and restoring

Re: [PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-29 Thread David Woodhouse
On Mon, 2018-01-29 at 01:58 +0100, KarimAllah Ahmed wrote: > Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for > guests that will only mitigate Spectre V2 through IBRS+IBPB and will not > be using a retpoline+IBPB based approach. > > To avoid the overhead of atomically saving

Re: [PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-29 Thread David Woodhouse
On Mon, 2018-01-29 at 01:58 +0100, KarimAllah Ahmed wrote: > Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for > guests that will only mitigate Spectre V2 through IBRS+IBPB and will not > be using a retpoline+IBPB based approach. > > To avoid the overhead of atomically saving

[PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-28 Thread KarimAllah Ahmed
Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for guests that will only mitigate Spectre V2 through IBRS+IBPB and will not be using a retpoline+IBPB based approach. To avoid the overhead of atomically saving and restoring the MSR_IA32_SPEC_CTRL for guests that do not actually

[PATCH v2 2/4] x86: vmx: Allow direct access to MSR_IA32_SPEC_CTRL

2018-01-28 Thread KarimAllah Ahmed
Add direct access to MSR_IA32_SPEC_CTRL for guests. This is needed for guests that will only mitigate Spectre V2 through IBRS+IBPB and will not be using a retpoline+IBPB based approach. To avoid the overhead of atomically saving and restoring the MSR_IA32_SPEC_CTRL for guests that do not actually