On Wed, Jan 02, 2013 at 03:39:03PM +0100, Andreas Färber wrote: > Am 28.12.2012 19:37, schrieb Eduardo Habkost: > > The existing -cpu host code simply set every bit inside svm_features > > (initializing it to -1), and that makes it impossible to make the > > enforce/check options work properly when the user asks for SVM features > > explicitly in the command-line. > > > > So, instead of initializing svm_features to -1, use GET_SUPPORTED_CPUID > > to fill only the bits that are supported by the host (just like we do > > for all other CPUID feature words inside kvm_cpu_fill_host()). > > > > This will keep the existing behavior (as filter_features_for_kvm() > > already uses GET_SUPPORTED_CPUID to filter svm_features), but will allow > > us to properly check for KVM features inside > > kvm_check_features_against_host() later. > > > > For example, we will be able to make this: > > > > $ qemu-system-x86_64 -cpu ...,+pfthreshold,enforce > > > > refuse to start if the SVM "pfthreshold" feature is not supported by the > > host (after we fix kvm_check_features_against_host() to check SVM flags > > as well). > > > > Signed-off-by: Eduardo Habkost <ehabkost@xxxxxxxxxx> > > --- > > target-i386/cpu.c | 11 ++++------- > > 1 file changed, 4 insertions(+), 7 deletions(-) > > > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > > index 3cd1cee..6e2d32d 100644 > > --- a/target-i386/cpu.c > > +++ b/target-i386/cpu.c > > @@ -897,13 +897,10 @@ static void kvm_cpu_fill_host(x86_def_t *x86_cpu_def) > > } > > } > > > > - /* > > - * Every SVM feature requires emulation support in KVM - so we can't just > > - * read the host features here. KVM might even support SVM features not > > - * available on the host hardware. Just set all bits and mask out the > > - * unsupported ones later. > > - */ > > - x86_cpu_def->svm_features = -1; > > + /* Other KVM-specific feature fields: */ > > + x86_cpu_def->svm_features = > > + kvm_arch_get_supported_cpuid(s, 0x8000000A, 0, R_EDX); > > Is there no #define for this, similar to KVM_CPUID_FEATURES in 2/2? I believve KVM_CPUID_FEATURES is the exception, all other leaves have their own numbers hardcoded in the code. (The way I plan to fix this is to introduce the feature-array and a CPUID leaf/register table for the feature-array, so kvm_cpu_fill_host(), filter_features_for_kvm(), kvm_check_features_against_host() & similar functions would always handle exactly the same set of CPUID leaves, by simply looking at the table). > FWIW indentation looks odd. Oops, I intended to follow the existing style used for ext2_features and ext3_features and use 8 spaces instead of 12. I will resubmit. -- Eduardo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
