Messages in this thread | | | Date | Wed, 05 May 2010 11:23:28 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH v2 4/7] export paravirtual cpuid flags in KVM_GET_SUPPORTED_CPUID |
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On 05/03/2010 06:52 PM, Glauber Costa wrote: > Right now, we were using individual KVM_CAP entities to communicate > userspace about which cpuids we support. This is suboptimal, since it > generates a delay between the feature arriving in the host, and > being available at the guest. > > A much better mechanism is to list para features in KVM_GET_SUPPORTED_CPUID. > This makes userspace automatically aware of what we provide. And if we > ever add a new cpuid bit in the future, we have to do that again, > which create some complexity and delay in feature adoption. > > Signed-off-by: Glauber Costa<glommer@redhat.com> > --- > arch/x86/include/asm/kvm_para.h | 4 ++++ > arch/x86/kvm/x86.c | 27 +++++++++++++++++++++++++++ > 2 files changed, 31 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h > index 9734808..f019f8c 100644 > --- a/arch/x86/include/asm/kvm_para.h > +++ b/arch/x86/include/asm/kvm_para.h > @@ -16,6 +16,10 @@ > #define KVM_FEATURE_CLOCKSOURCE 0 > #define KVM_FEATURE_NOP_IO_DELAY 1 > #define KVM_FEATURE_MMU_OP 2 > +/* This indicates that the new set of kvmclock msrs > + * are available. The use of 0x11 and 0x12 is deprecated > + */ > +#define KVM_FEATURE_CLOCKSOURCE2 3 >
Separate patch.
> > #define MSR_KVM_WALL_CLOCK 0x11 > #define MSR_KVM_SYSTEM_TIME 0x12 > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index eb84947..8a7cdda 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1971,6 +1971,20 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > } > break; > } > + case 0x40000000: { >
Use symbolic name, please.
> + char signature[] = "KVMKVMKVM"; > + u32 *sigptr = (u32 *)signature; > + entry->eax = 1; >
Where did this come from?
> + entry->ebx = sigptr[0]; > + entry->ecx = sigptr[1]; > + entry->edx = sigptr[2]; >
Overflow, you're reading 12 bytes from a 10-byte variable.
> + break; > + } > + case 0x40000001: > + entry->eax = (1<< KVM_FEATURE_CLOCKSOURCE) | > + (1<< KVM_FEATURE_NOP_IO_DELAY) | > + (1<< KVM_FEATURE_CLOCKSOURCE2); >
Indentation...
Also, have to initialize all fields, since the real cpu won't initialize them for you.
Sidenote: the real cpu may be a kvm vcpu, so it may in fact support those features.
> + break; > case 0x80000000: > entry->eax = min(entry->eax, 0x8000001a); > break; > @@ -2017,6 +2031,19 @@ static int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid, > for (func = 0x80000001; func<= limit&& nent< cpuid->nent; ++func) > do_cpuid_ent(&cpuid_entries[nent], func, 0, > &nent, cpuid->nent); > + > + > + > + r = -E2BIG; > + if (nent>= cpuid->nent) > + goto out_free; > + > + do_cpuid_ent(&cpuid_entries[nent], 0x40000000, 0,&nent, cpuid->nent); > + limit = cpuid_entries[nent - 1].eax; >
The kvm cpuid does not follow the limit thing.
> + for (func = 0x40000001; func<= limit&& nent< cpuid->nent; ++func) > + do_cpuid_ent(&cpuid_entries[nent], func, 0, > + &nent, cpuid->nent); > + > r = -E2BIG; >
To avoid confusion, please write Documentation/kvm/cpuid.txt based on the current qemu-kvm code, and implement this patch according to the documentation.
-- error compiling committee.c: too many arguments to function
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