On 18/11/2014 10:14, Tiejun Chen wrote:
> Actually MMIO_MAX_GEN is same as MMIO_GEN_MASK, and
> especially in all cases we already AND this so its
> also unnecessary to generate such a WARN_ON().
>
> Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
Good idea, but I actually prefer keeping MMIO_GEN_MASK since it is often
used together with an "&".
Then, the WARN_ON is better written as
- WARN_ON(gen > MMIO_MAX_GEN);
+ WARN_ON(gen & ~MMIO_GEN_MASK);
Paolo
> ---
> arch/x86/kvm/mmu.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index ac1c4de..7712345 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -213,15 +213,12 @@ EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);
> #define MMIO_GEN_SHIFT 20
> #define MMIO_GEN_LOW_SHIFT 10
> #define MMIO_GEN_LOW_MASK ((1 << MMIO_GEN_LOW_SHIFT) - 2)
> -#define MMIO_GEN_MASK ((1 << MMIO_GEN_SHIFT) - 1)
> #define MMIO_MAX_GEN ((1 << MMIO_GEN_SHIFT) - 1)
>
> static u64 generation_mmio_spte_mask(unsigned int gen)
> {
> u64 mask;
>
> - WARN_ON(gen > MMIO_MAX_GEN);
> -
> mask = (gen & MMIO_GEN_LOW_MASK) << MMIO_SPTE_GEN_LOW_SHIFT;
> mask |= ((u64)gen >> MMIO_GEN_LOW_SHIFT) << MMIO_SPTE_GEN_HIGH_SHIFT;
> return mask;
> @@ -240,7 +237,7 @@ static unsigned int get_mmio_spte_generation(u64 spte)
>
> static unsigned int kvm_current_mmio_generation(struct kvm *kvm)
> {
> - return kvm_memslots(kvm)->generation & MMIO_GEN_MASK;
> + return kvm_memslots(kvm)->generation & MMIO_MAX_GEN;
> }
>
> static void mark_mmio_spte(struct kvm *kvm, u64 *sptep, u64 gfn,
>
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