Re: [PATCH 2/3] KVM: x86: hyper-v: set NoNonArchitecturalCoreSharing CPUID bit when SMT is impossible

2019-09-23 Thread Paolo Bonzini
On 23/09/19 17:37, Peter Zijlstra wrote: >> This patch reports NoNonArchitecturalCoreSharing bit in to userspace in the >> first case. The second case is outside of KVM's domain of responsibility >> (as vCPU pinning is actually done by someone who manages KVM's userspace - >> e.g. libvirt pinning

Re: [PATCH 2/3] KVM: x86: hyper-v: set NoNonArchitecturalCoreSharing CPUID bit when SMT is impossible

2019-09-23 Thread Peter Zijlstra
On Mon, Sep 16, 2019 at 06:22:57PM +0200, Vitaly Kuznetsov wrote: > Hyper-V 2019 doesn't expose MD_CLEAR CPUID bit to guests when it cannot > guarantee that two virtual processors won't end up running on sibling SMT > threads without knowing about it. This is done as an optimization as in > this

Re: [PATCH 2/3] KVM: x86: hyper-v: set NoNonArchitecturalCoreSharing CPUID bit when SMT is impossible

2019-09-17 Thread Paolo Bonzini
On 17/09/19 11:33, Vitaly Kuznetsov wrote: > Jim Mattson writes: > >> On Mon, Sep 16, 2019 at 9:23 AM Vitaly Kuznetsov wrote: >>> >>> Hyper-V 2019 doesn't expose MD_CLEAR CPUID bit to guests when it cannot >>> guarantee that two virtual processors won't end up running on sibling SMT >>> threads

Re: [PATCH 2/3] KVM: x86: hyper-v: set NoNonArchitecturalCoreSharing CPUID bit when SMT is impossible

2019-09-17 Thread Vitaly Kuznetsov
Jim Mattson writes: > On Mon, Sep 16, 2019 at 9:23 AM Vitaly Kuznetsov wrote: >> >> Hyper-V 2019 doesn't expose MD_CLEAR CPUID bit to guests when it cannot >> guarantee that two virtual processors won't end up running on sibling SMT >> threads without knowing about it. This is done as an

Re: [PATCH 2/3] KVM: x86: hyper-v: set NoNonArchitecturalCoreSharing CPUID bit when SMT is impossible

2019-09-16 Thread Jim Mattson
On Mon, Sep 16, 2019 at 9:23 AM Vitaly Kuznetsov wrote: > > Hyper-V 2019 doesn't expose MD_CLEAR CPUID bit to guests when it cannot > guarantee that two virtual processors won't end up running on sibling SMT > threads without knowing about it. This is done as an optimization as in > this case

[PATCH 2/3] KVM: x86: hyper-v: set NoNonArchitecturalCoreSharing CPUID bit when SMT is impossible

2019-09-16 Thread Vitaly Kuznetsov
Hyper-V 2019 doesn't expose MD_CLEAR CPUID bit to guests when it cannot guarantee that two virtual processors won't end up running on sibling SMT threads without knowing about it. This is done as an optimization as in this case there is nothing the guest can do to protect itself against MDS and