diff options
| -rw-r--r-- | arch/x86/kvm/mmu.c | 86 |
1 files changed, 71 insertions, 15 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 982718f..a22b5fe 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -259,26 +259,82 @@ static gfn_t pse36_gfn_delta(u32 gpte) return (gpte & PT32_DIR_PSE36_MASK) << shift; } +#ifdef CONFIG_X86_64 static void __set_spte(u64 *sptep, u64 spte) { - set_64bit(sptep, spte); + *sptep = spte; } -static u64 __xchg_spte(u64 *sptep, u64 new_spte) +static void __update_clear_spte_fast(u64 *sptep, u64 spte) { -#ifdef CONFIG_X86_64 - return xchg(sptep, new_spte); + *sptep = spte; +} + +static u64 __update_clear_spte_slow(u64 *sptep, u64 spte) +{ + return xchg(sptep, spte); +} #else - u64 old_spte; +union split_spte { + struct { + u32 spte_low; + u32 spte_high; + }; + u64 spte; +}; - do { - old_spte = *sptep; - } while (cmpxchg64(sptep, old_spte, new_spte) != old_spte); +static void __set_spte(u64 *sptep, u64 spte) +{ + union split_spte *ssptep, sspte; - return old_spte; -#endif + ssptep = (union split_spte *)sptep; + sspte = (union split_spte)spte; + + ssptep->spte_high = sspte.spte_high; + + /* + * If we map the spte from nonpresent to present, We should store + * the high bits firstly, then set present bit, so cpu can not + * fetch this spte while we are setting the spte. + */ + smp_wmb(); + + ssptep->spte_low = sspte.spte_low; } +static void __update_clear_spte_fast(u64 *sptep, u64 spte) +{ + union split_spte *ssptep, sspte; + + ssptep = (union split_spte *)sptep; + sspte = (union split_spte)spte; + + ssptep->spte_low = sspte.spte_low; + + /* + * If we map the spte from present to nonpresent, we should clear + * present bit firstly to avoid vcpu fetch the old high bits. + */ + smp_wmb(); + + ssptep->spte_high = sspte.spte_high; +} + +static u64 __update_clear_spte_slow(u64 *sptep, u64 spte) +{ + union split_spte *ssptep, sspte, orig; + + ssptep = (union split_spte *)sptep; + sspte = (union split_spte)spte; + + /* xchg acts as a barrier before the setting of the high bits */ + orig.spte_low = xchg(&ssptep->spte_low, sspte.spte_low); + orig.spte_high = ssptep->spte_high = sspte.spte_high; + + return orig.spte; +} +#endif + static bool spte_has_volatile_bits(u64 spte) { if (!shadow_accessed_mask) @@ -330,9 +386,9 @@ static void mmu_spte_update(u64 *sptep, u64 new_spte) mask |= shadow_dirty_mask; if (!spte_has_volatile_bits(old_spte) || (new_spte & mask) == mask) - __set_spte(sptep, new_spte); + __update_clear_spte_fast(sptep, new_spte); else - old_spte = __xchg_spte(sptep, new_spte); + old_spte = __update_clear_spte_slow(sptep, new_spte); if (!shadow_accessed_mask) return; @@ -354,9 +410,9 @@ static int mmu_spte_clear_track_bits(u64 *sptep) u64 old_spte = *sptep; if (!spte_has_volatile_bits(old_spte)) - __set_spte(sptep, 0ull); + __update_clear_spte_fast(sptep, 0ull); else - old_spte = __xchg_spte(sptep, 0ull); + old_spte = __update_clear_spte_slow(sptep, 0ull); if (!is_rmap_spte(old_spte)) return 0; @@ -376,7 +432,7 @@ static int mmu_spte_clear_track_bits(u64 *sptep) */ static void mmu_spte_clear_no_track(u64 *sptep) { - __set_spte(sptep, 0ull); + __update_clear_spte_fast(sptep, 0ull); } static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache, |