| Message ID | 1344505734-16005-1-git-send-email-stefan.bader@canonical.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Aug 09, 2012 at 11:48:54AM +0200, Stefan Bader wrote: > Since adding the RDPMC feature in kernels after 3.3, a guest > running a v3.3+ kernel on a host running 3.2 cannot load the > kvm-intel module (Intel CPU obviously). The reason is a check > made on module load time for that feature being present in the > MSRs passed to the guest. > Upstreams reasoning is that no real CPU ever had this flag so > they do not want to change the check in newer kernels (while > kvm-amd is not so tight). I thought it was that no real CPU didn't have this feature, so they could rely on its existance. But anyhow... > So from the patch that added support for RDPMC based exiting, > only the bit that adds the feature to the nested MSR is taken. > > I tested this and could load the module, bring up a nested guest > and also ran "perf test" which on newer versions does a RDPMC > test that fails gracefully enough to seem ok (syscall returns > error). > > This was proposed for stable and I just saw the emails being > sent but since it has some impact on Quantal testing I want > to make sure this gets in as soon as possible. > > -Stefan > > From b79a5f03b4d9a1a56949d6ef38fd4879ff1b8aee Mon Sep 17 00:00:00 2001 > From: Stefan Bader <stefan.bader@canonical.com> > Date: Thu, 10 Nov 2011 14:57:25 +0200 > Subject: [PATCH] UBUNTU: (pre-stable) KVM: VMX: Set CPU_BASED_RDPMC_EXITING for nested > > Based on commit fee84b079d5ddee2247b5c1f53162c330c622902 upstream. > > Intercept RDPMC and forward it to the PMU emulation code. > > Newer vmx support will only allow to load the kvm_intel module > if RDPMC_EXITING is supported. Even without the actual support > this part of the change is required on 3.2 hosts. > > BugLink: http://bugs.launchpad.net/bugs/1031090 > Signed-off-by: Stefan Bader <stefan.bader@canonical.com> > --- > arch/x86/kvm/vmx.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 114fe29..94e6749 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -1957,6 +1957,7 @@ static __init void nested_vmx_setup_ctls_msrs(void) > #endif > CPU_BASED_MOV_DR_EXITING | CPU_BASED_UNCOND_IO_EXITING | > CPU_BASED_USE_IO_BITMAPS | CPU_BASED_MONITOR_EXITING | > + CPU_BASED_RDPMC_EXITING | > CPU_BASED_ACTIVATE_SECONDARY_CONTROLS; > /* > * We can allow some features even when not supported by the Having followed the development of this patch I believe this is the minimum needed to get nested VMs startable on Intel. The testing I have seen looks good. Acked-by: Andy Whitcroft <apw@canonical.com> -apw
On 09.08.2012 11:48, Stefan Bader wrote: > Since adding the RDPMC feature in kernels after 3.3, a guest > running a v3.3+ kernel on a host running 3.2 cannot load the > kvm-intel module (Intel CPU obviously). The reason is a check > made on module load time for that feature being present in the > MSRs passed to the guest. > Upstreams reasoning is that no real CPU ever had this flag so > they do not want to change the check in newer kernels (while > kvm-amd is not so tight). Of course the reason was that every real CPU *has* the feature (at least the one doing virt). Lost in negations. Doh! > > So from the patch that added support for RDPMC based exiting, > only the bit that adds the feature to the nested MSR is taken. > > I tested this and could load the module, bring up a nested guest > and also ran "perf test" which on newer versions does a RDPMC > test that fails gracefully enough to seem ok (syscall returns > error). > > This was proposed for stable and I just saw the emails being > sent but since it has some impact on Quantal testing I want > to make sure this gets in as soon as possible. > > -Stefan > > From b79a5f03b4d9a1a56949d6ef38fd4879ff1b8aee Mon Sep 17 00:00:00 2001 > From: Stefan Bader <stefan.bader@canonical.com> > Date: Thu, 10 Nov 2011 14:57:25 +0200 > Subject: [PATCH] UBUNTU: (pre-stable) KVM: VMX: Set CPU_BASED_RDPMC_EXITING for nested > > Based on commit fee84b079d5ddee2247b5c1f53162c330c622902 upstream. > > Intercept RDPMC and forward it to the PMU emulation code. > > Newer vmx support will only allow to load the kvm_intel module > if RDPMC_EXITING is supported. Even without the actual support > this part of the change is required on 3.2 hosts. > > BugLink: http://bugs.launchpad.net/bugs/1031090 > Signed-off-by: Stefan Bader <stefan.bader@canonical.com> > --- > arch/x86/kvm/vmx.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 114fe29..94e6749 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -1957,6 +1957,7 @@ static __init void nested_vmx_setup_ctls_msrs(void) > #endif > CPU_BASED_MOV_DR_EXITING | CPU_BASED_UNCOND_IO_EXITING | > CPU_BASED_USE_IO_BITMAPS | CPU_BASED_MONITOR_EXITING | > + CPU_BASED_RDPMC_EXITING | > CPU_BASED_ACTIVATE_SECONDARY_CONTROLS; > /* > * We can allow some features even when not supported by the >
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 114fe29..94e6749 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1957,6 +1957,7 @@ static __init void nested_vmx_setup_ctls_msrs(void) #endif CPU_BASED_MOV_DR_EXITING | CPU_BASED_UNCOND_IO_EXITING | CPU_BASED_USE_IO_BITMAPS | CPU_BASED_MONITOR_EXITING | + CPU_BASED_RDPMC_EXITING | CPU_BASED_ACTIVATE_SECONDARY_CONTROLS; /* * We can allow some features even when not supported by the