On Sun, 2008-11-16 at 05:26 -0800, Avi Kivity wrote:
> Kamble, Nitin A wrote:
> >> The capability itself can return the count; for example
> >>
> >> case KVM_CAP_NR_CPUID_LEAVES:
> >> return KVM_MAX_CPUID_ENTRIES;
> >>
> >> which is simpler to use and shorter.
> >>
> >
> > Avi,
> > Yes, it is simpler and shorter, but is returning a constant. It will be
> > wasting space for the unused entries. Also it put's a restriction that the
> > list count can not go more than that.
> > The dynamic size finding, the patch I sent, is not complicated or long
> > to be an issue. Would you like to give another consideration for the same
> > patch (patch-3) I sent earlier?
> >
> >
>
> Oh, I confused the sizing code with something else.
>
> We can add this, but older kernels will still miss the code so we have
> to work around it. I guess userspace can start with a large number, and
> double it each time the ioctl fails.
Avi,
You mean older kernels which does not support the KVM_CAP_CPUID_SIZER
ioctl.
Two ways to handle it:
1. qemu giving error that "-cpu host" option is not supported on this
kernel.
2. or as per your suggestion guess it in userland.
Either way it is code for kvm-userspace.git tree.
I am attaching the patch again. Please apply.
BTW I did not get your opinion for the patch for the kvm-userspace.git
tree. Would you comment on it please?
--
Thanks & Regards,
Nitin
Open Source Technology Center, Intel Corporation
-----------------------------------------------------------------
The mind is like a parachute; it works much better when it's open
commit 70e4e65bc591eb9cf25c1cbc0d16b2cbdb089a6f
Author: Nitin A Kamble <[EMAIL PROTECTED]>
Date: Wed Nov 5 16:17:46 2008 -0800
Change the ioctl KVM_GET_SUPPORTED_CPUID, such that it will return the
no of entries in the list when requested no of entries (nent) is 0.
Also add another KVM_CHECK_EXTENSION, KVM_CAP_CPUID_SIZER to determine
if the running kernel supports the above changed ABI.
Signed-Off-By: Nitin A Kamble <[EMAIL PROTECTED]>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 09e6c56..e50db11 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -86,7 +86,7 @@
#define KVM_NUM_MMU_PAGES (1 << KVM_MMU_HASH_SHIFT)
#define KVM_MIN_FREE_MMU_PAGES 5
#define KVM_REFILL_PAGES 25
-#define KVM_MAX_CPUID_ENTRIES 40
+#define KVM_MAX_CPUID_ENTRIES 100
#define KVM_NR_FIXED_MTRR_REGION 88
#define KVM_NR_VAR_MTRR 8
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bf7461b..52e6207 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -969,6 +969,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_NOP_IO_DELAY:
case KVM_CAP_MP_STATE:
case KVM_CAP_SYNC_MMU:
+ case KVM_CAP_CPUID_SIZER:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -1303,10 +1304,14 @@ static int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
{
struct kvm_cpuid_entry2 *cpuid_entries;
int limit, nent = 0, r = -E2BIG;
+ int sizer = 0;
u32 func;
- if (cpuid->nent < 1)
- goto out;
+ if (cpuid->nent == 0) {
+ sizer = 1;
+ cpuid->nent = KVM_MAX_CPUID_ENTRIES;
+ }
+
r = -ENOMEM;
cpuid_entries = vmalloc(sizeof(struct kvm_cpuid_entry2) * cpuid->nent);
if (!cpuid_entries)
@@ -1327,9 +1332,11 @@ static int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
do_cpuid_ent(&cpuid_entries[nent], func, 0,
&nent, cpuid->nent);
r = -EFAULT;
- if (copy_to_user(entries, cpuid_entries,
+ if (!sizer) {
+ if (copy_to_user(entries, cpuid_entries,
nent * sizeof(struct kvm_cpuid_entry2)))
- goto out_free;
+ goto out_free;
+ }
cpuid->nent = nent;
r = 0;
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 44fd7fa..d4cb8b1 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -392,6 +392,9 @@ struct kvm_trace_rec {
#endif
#define KVM_CAP_IOMMU 18
#define KVM_CAP_NMI 19
+#define KVM_CAP_CPUID_SIZER 20 /* return of 1 means the KVM_GET_SUPPORTED_CPUID */
+ /* ioctl will return the size of list when input */
+ /* list size (nent) is 0 */
/*
* ioctls for VM fds
