diff options
| -rw-r--r-- | arch/x86/kvm/cpuid.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 67e9f79fe059..e961e9a05847 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -11,6 +11,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/kvm_host.h> +#include "linux/lockdep.h" #include <linux/export.h> #include <linux/vmalloc.h> #include <linux/uaccess.h> @@ -84,6 +85,18 @@ static inline struct kvm_cpuid_entry2 *cpuid_entry2_find( struct kvm_cpuid_entry2 *e; int i; + /* + * KVM has a semi-arbitrary rule that querying the guest's CPUID model + * with IRQs disabled is disallowed. The CPUID model can legitimately + * have over one hundred entries, i.e. the lookup is slow, and IRQs are + * typically disabled in KVM only when KVM is in a performance critical + * path, e.g. the core VM-Enter/VM-Exit run loop. Nothing will break + * if this rule is violated, this assertion is purely to flag potential + * performance issues. If this fires, consider moving the lookup out + * of the hotpath, e.g. by caching information during CPUID updates. + */ + lockdep_assert_irqs_enabled(); + for (i = 0; i < nent; i++) { e = &entries[i]; |