[PATCH] KVM: fix XSAVE bit scanning (now properly)

[PATCH] KVM: fix XSAVE bit scanning (now properly)

[Andre Przywara]

commit 123108f1c1aafd51d6a5c79cc04d7999dd88a930 tried to fix KVMs
XSAVE valid feature scanning, but it was wrong. It was not considering
the sparse nature of this bitfield, instead reading values from
uninitialized members of the entries array.
This patch now separates subleaf indicies from KVM's array indicies
and fills the entry before querying it's value.
This fixes AVX support in KVM guests.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
---
 arch/x86/kvm/x86.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 694538a..2a52e69 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2418,16 +2418,17 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 		break;
 	}
 	case 0xd: {
-		int i;
+		int idx, i;
 
 		entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
-		for (i = 1; *nent < maxnent && i < 64; ++i) {
-			if (entry[i].eax == 0 || !supported_xcr0_bit(i))
+		for (idx = 1, i = 1; *nent < maxnent && idx < 64; ++idx) {
+			do_cpuid_1_ent(&entry[i], function, idx);
+			if (entry[i].eax == 0 || !supported_xcr0_bit(idx))
 				continue;
-			do_cpuid_1_ent(&entry[i], function, i);
 			entry[i].flags |=
 			       KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
 			++*nent;
+			++i;
 		}
 		break;
 	}
-- 
1.6.4

Re: [PATCH] KVM: fix XSAVE bit scanning (now properly)

[Avi Kivity]

On 06/10/2011 12:35 PM, Andre Przywara wrote:
> commit 123108f1c1aafd51d6a5c79cc04d7999dd88a930 tried to fix KVMs
> XSAVE valid feature scanning, but it was wrong. It was not considering
> the sparse nature of this bitfield, instead reading values from
> uninitialized members of the entries array.
> This patch now separates subleaf indicies from KVM's array indicies
> and fills the entry before querying it's value.
> This fixes AVX support in KVM guests.

Applied, thanks.

-- 
error compiling committee.c: too many arguments to function