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Subject[PATCH AUTOSEL 5.3 25/68] kvm: x86: Fix a spurious -E2BIG in __do_cpuid_func
Date
From: Jim Mattson <jmattson@google.com>

[ Upstream commit a1a640b8c0cd8a2a7f84ab694f04bc64dc6988af ]

Don't return -E2BIG from __do_cpuid_func when processing function 0BH
or 1FH and the last interesting subleaf occupies the last allocated
entry in the result array.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Fixes: 831bf664e9c1fc ("KVM: Refactor and simplify kvm_dev_ioctl_get_supported_cpuid")
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/cpuid.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e7d25f4364664..429648ae5653f 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -612,16 +612,20 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
*/
case 0x1f:
case 0xb: {
- int i, level_type;
+ int i;

- /* read more entries until level_type is zero */
- for (i = 1; ; ++i) {
+ /*
+ * We filled in entry[0] for CPUID(EAX=<function>,
+ * ECX=00H) above. If its level type (ECX[15:8]) is
+ * zero, then the leaf is unimplemented, and we're
+ * done. Otherwise, continue to populate entries
+ * until the level type (ECX[15:8]) of the previously
+ * added entry is zero.
+ */
+ for (i = 1; entry[i - 1].ecx & 0xff00; ++i) {
if (*nent >= maxnent)
goto out;

- level_type = entry[i - 1].ecx & 0xff00;
- if (!level_type)
- break;
do_host_cpuid(&entry[i], function, i);
++*nent;
}
--
2.20.1
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