| Message ID | 1356719854-16401-3-git-send-email-ehabkost@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Fri, 28 Dec 2012 16:37:34 -0200 Eduardo Habkost <ehabkost@redhat.com> wrote: > When using -cpu host, we don't need to use the kvm_default_features > variable, as the user is explicitly asking QEMU to enable all feature > supported by the host. > > This changes the kvm_cpu_fill_host() code to use GET_SUPPORTED_CPUID to > initialize the kvm_features field, so we get all host KVM features > enabled. 1_2 and 1_3 compat machines diff on pv_eoi flag, with this patch 1_2 might have it set. Is it ok from compat machines pov? > > This will also allow use to properly check/enforce KVM features inside > kvm_check_features_against_host() later. For example, we will be able to > make this: > > $ qemu-system-x86_64 -cpu ...,+kvm_pv_eoi,enforce > > refuse to start if kvm_pv_eoi is not supported by the host (after we fix > kvm_check_features_against_host() to check KVM flags as well). It would be nice to have kvm_check_features_against_host() patch in this series to verify that this patch and previous patch works as expected. > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> > --- > target-i386/cpu.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > index 6e2d32d..76f19f0 100644 > --- a/target-i386/cpu.c > +++ b/target-i386/cpu.c > @@ -900,6 +900,8 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def) > /* Other KVM-specific feature fields: */ > x86_cpu_def->svm_features = > kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX); > + x86_cpu_def->kvm_features = > + kvm_arch_get_supported_cpuid(s, KVM_CPUID_FEATURES, 0, > R_EAX); > #endif /* CONFIG_KVM */ > }
On Wed, Jan 02, 2013 at 03:52:45PM +0100, Igor Mammedov wrote: > On Fri, 28 Dec 2012 16:37:34 -0200 > Eduardo Habkost <ehabkost@redhat.com> wrote: > > > When using -cpu host, we don't need to use the kvm_default_features > > variable, as the user is explicitly asking QEMU to enable all feature > > supported by the host. > > > > This changes the kvm_cpu_fill_host() code to use GET_SUPPORTED_CPUID to > > initialize the kvm_features field, so we get all host KVM features > > enabled. > > 1_2 and 1_3 compat machines diff on pv_eoi flag, with this patch 1_2 might > have it set. > Is it ok from compat machines pov? -cpu host is completely dependent on host hardware and kernel version, there are no compatibility expectations. > > > > > This will also allow use to properly check/enforce KVM features inside > > kvm_check_features_against_host() later. For example, we will be able to > > make this: > > > > $ qemu-system-x86_64 -cpu ...,+kvm_pv_eoi,enforce > > > > refuse to start if kvm_pv_eoi is not supported by the host (after we fix > > kvm_check_features_against_host() to check KVM flags as well). > It would be nice to have kvm_check_features_against_host() patch in this > series to verify that this patch and previous patch works as expected. The kvm_check_features_against_host() change would be a user-visible behavior change, and I wanted to keep the changes minimal by now. (the main reason I submitted this earlier is to make it easier to clean up the init code for CPU subclasses) I was planning to introduce those behavior changes only after introducing the feature-word array, so the kvm_check_features_against_host() code can become simpler and easier to review (instead of adding 4 additional items to the messy struct model_features_t array). But if you think we can introduce those changes now, I will be happy to send a series that changes that code as well. > > > > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> > > --- > > target-i386/cpu.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > index 6e2d32d..76f19f0 100644 > > --- a/target-i386/cpu.c > > +++ b/target-i386/cpu.c > > @@ -900,6 +900,8 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def) > > /* Other KVM-specific feature fields: */ > > x86_cpu_def->svm_features = > > kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX); > > + x86_cpu_def->kvm_features = > > + kvm_arch_get_supported_cpuid(s, KVM_CPUID_FEATURES, 0, > > R_EAX); > > #endif /* CONFIG_KVM */ > > } >
On Wed, 2 Jan 2013 13:29:10 -0200 Eduardo Habkost <ehabkost@redhat.com> wrote: > On Wed, Jan 02, 2013 at 03:52:45PM +0100, Igor Mammedov wrote: > > On Fri, 28 Dec 2012 16:37:34 -0200 > > Eduardo Habkost <ehabkost@redhat.com> wrote: > > > > > When using -cpu host, we don't need to use the kvm_default_features > > > variable, as the user is explicitly asking QEMU to enable all feature > > > supported by the host. > > > > > > This changes the kvm_cpu_fill_host() code to use GET_SUPPORTED_CPUID to > > > initialize the kvm_features field, so we get all host KVM features > > > enabled. > > > > 1_2 and 1_3 compat machines diff on pv_eoi flag, with this patch 1_2 might > > have it set. > > Is it ok from compat machines pov? > > -cpu host is completely dependent on host hardware and kernel version, > there are no compatibility expectations. It's still kind of unpleasant surprise if on the same host "qemu-1.3 -cpu host -machine pc-1.2" and "qemu-1.3+ -cpu host -machine pc-1.2" would give different pv_eoi feature default, where pv-eoi should be available after -machine pc-1.2 by default. > > > > > > > > > This will also allow use to properly check/enforce KVM features inside > > > kvm_check_features_against_host() later. For example, we will be able to > > > make this: > > > > > > $ qemu-system-x86_64 -cpu ...,+kvm_pv_eoi,enforce > > > > > > refuse to start if kvm_pv_eoi is not supported by the host (after we fix > > > kvm_check_features_against_host() to check KVM flags as well). > > It would be nice to have kvm_check_features_against_host() patch in this > > series to verify that this patch and previous patch works as expected. > > The kvm_check_features_against_host() change would be a user-visible > behavior change, and I wanted to keep the changes minimal by now. (the > main reason I submitted this earlier is to make it easier to clean up > the init code for CPU subclasses) > > I was planning to introduce those behavior changes only after > introducing the feature-word array, so the kvm_check_features_against_host() > code can become simpler and easier to review (instead of adding 4 > additional items to the messy struct model_features_t array). But if you > think we can introduce those changes now, I will be happy to send a > series that changes that code as well. It would be better if it and simplifying kvm_check_features_against_host() were in here together. > > > > > > > > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> > > > --- > > > target-i386/cpu.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > > index 6e2d32d..76f19f0 100644 > > > --- a/target-i386/cpu.c > > > +++ b/target-i386/cpu.c > > > @@ -900,6 +900,8 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def) > > > /* Other KVM-specific feature fields: */ > > > x86_cpu_def->svm_features = > > > kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX); > > > + x86_cpu_def->kvm_features = > > > + kvm_arch_get_supported_cpuid(s, KVM_CPUID_FEATURES, 0, > > > R_EAX); > > > #endif /* CONFIG_KVM */ > > > } > > > > -- > Eduardo >
On Wed, Jan 02, 2013 at 09:30:20PM +0100, Igor Mammedov wrote: > On Wed, 2 Jan 2013 13:29:10 -0200 > Eduardo Habkost <ehabkost@redhat.com> wrote: > > > On Wed, Jan 02, 2013 at 03:52:45PM +0100, Igor Mammedov wrote: > > > On Fri, 28 Dec 2012 16:37:34 -0200 > > > Eduardo Habkost <ehabkost@redhat.com> wrote: > > > > > > > When using -cpu host, we don't need to use the kvm_default_features > > > > variable, as the user is explicitly asking QEMU to enable all feature > > > > supported by the host. > > > > > > > > This changes the kvm_cpu_fill_host() code to use GET_SUPPORTED_CPUID to > > > > initialize the kvm_features field, so we get all host KVM features > > > > enabled. > > > > > > 1_2 and 1_3 compat machines diff on pv_eoi flag, with this patch 1_2 might > > > have it set. > > > Is it ok from compat machines pov? > > > > -cpu host is completely dependent on host hardware and kernel version, > > there are no compatibility expectations. > > It's still kind of unpleasant surprise if on the same host > "qemu-1.3 -cpu host -machine pc-1.2" and "qemu-1.3+ -cpu host -machine pc-1.2" > would give different pv_eoi feature default, where pv-eoi should be > available after -machine pc-1.2 by default. Just like you may end up getting new features enabled by -cpu host after upgrading the kernel, you may end up getting new features enabled by -cpu host after upgrading qemu. If you don't like surprises, don't use -cpu host. ;-) I don't think machine-types exist to avoid user surprise, they exist to keep compatibility (which is not expected to happen when using -cpu host). Keeping compatibility is hard enough in the cases where we really need it, I don't think it is worth the extra work and complexity for an use case where compatibility is not expected. > > > > > > > > > > > > > > This will also allow use to properly check/enforce KVM features inside > > > > kvm_check_features_against_host() later. For example, we will be able to > > > > make this: > > > > > > > > $ qemu-system-x86_64 -cpu ...,+kvm_pv_eoi,enforce > > > > > > > > refuse to start if kvm_pv_eoi is not supported by the host (after we fix > > > > kvm_check_features_against_host() to check KVM flags as well). > > > It would be nice to have kvm_check_features_against_host() patch in this > > > series to verify that this patch and previous patch works as expected. > > > > The kvm_check_features_against_host() change would be a user-visible > > behavior change, and I wanted to keep the changes minimal by now. (the > > main reason I submitted this earlier is to make it easier to clean up > > the init code for CPU subclasses) > > > > I was planning to introduce those behavior changes only after > > introducing the feature-word array, so the kvm_check_features_against_host() > > code can become simpler and easier to review (instead of adding 4 > > additional items to the messy struct model_features_t array). But if you > > think we can introduce those changes now, I will be happy to send a > > series that changes that code as well. > It would be better if it and simplifying kvm_check_features_against_host() > were in here together. The best way I see to simplify kvm_check_features_against_host() requires the feature words array patch, that touches _lots_ of code. I wanted to avoid adding such an intrusive patch as a dependency. > > > > > > > > > > > > > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> > > > > --- > > > > target-i386/cpu.c | 2 ++ > > > > 1 file changed, 2 insertions(+) > > > > > > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > > > index 6e2d32d..76f19f0 100644 > > > > --- a/target-i386/cpu.c > > > > +++ b/target-i386/cpu.c > > > > @@ -900,6 +900,8 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def) > > > > /* Other KVM-specific feature fields: */ > > > > x86_cpu_def->svm_features = > > > > kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX); > > > > + x86_cpu_def->kvm_features = > > > > + kvm_arch_get_supported_cpuid(s, KVM_CPUID_FEATURES, 0, > > > > R_EAX); > > > > #endif /* CONFIG_KVM */ > > > > } > > > > > > > -- > > Eduardo > > > > > -- > Regards, > Igor
diff --git a/target-i386/cpu.c b/target-i386/cpu.c index 6e2d32d..76f19f0 100644 --- a/target-i386/cpu.c +++ b/target-i386/cpu.c @@ -900,6 +900,8 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def) /* Other KVM-specific feature fields: */ x86_cpu_def->svm_features = kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX); + x86_cpu_def->kvm_features = + kvm_arch_get_supported_cpuid(s, KVM_CPUID_FEATURES, 0, R_EAX); #endif /* CONFIG_KVM */ }
When using -cpu host, we don't need to use the kvm_default_features variable, as the user is explicitly asking QEMU to enable all feature supported by the host. This changes the kvm_cpu_fill_host() code to use GET_SUPPORTED_CPUID to initialize the kvm_features field, so we get all host KVM features enabled. This will also allow use to properly check/enforce KVM features inside kvm_check_features_against_host() later. For example, we will be able to make this: $ qemu-system-x86_64 -cpu ...,+kvm_pv_eoi,enforce refuse to start if kvm_pv_eoi is not supported by the host (after we fix kvm_check_features_against_host() to check KVM flags as well). Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> --- target-i386/cpu.c | 2 ++ 1 file changed, 2 insertions(+)