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KVM: MMU: introduce the rules to modify shadow page table 

Introduce some interfaces to modify spte as linux kernel does:
- mmu_spte_clear_track_bits, it set the spte from present to nonpresent, and
  track the stat bits(accessed/dirty) of spte
- mmu_spte_clear_no_track, the same as mmu_spte_clear_track_bits except
  tracking the stat bits
- mmu_spte_set, set spte from nonpresent to present
- mmu_spte_update, only update the stat bits

Now, it does not allowed to set spte from present to present, later, we can
drop the atomicly opration for X86_32 host, and it is the preparing work to
get spte on X86_32 host out of the mmu lock

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
hifive-unleashed-5.1
Xiao Guangrong 2011-07-12 03:30:35 +08:00 committed by Avi Kivity
parent d7c55201e6
commit 1df9f2dc39
1 changed files with 69 additions and 34 deletions
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103
arch/x86/kvm/mmu.c
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@ -299,12 +299,30 @@ static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask)
return (old_spte & bit_mask) && !(new_spte & bit_mask);
}
static void update_spte(u64 *sptep, u64 new_spte)
/* Rules for using mmu_spte_set:
* Set the sptep from nonpresent to present.
* Note: the sptep being assigned *must* be either not present
* or in a state where the hardware will not attempt to update
* the spte.
*/
static void mmu_spte_set(u64 *sptep, u64 new_spte)
{
WARN_ON(is_shadow_present_pte(*sptep));
__set_spte(sptep, new_spte);
}
/* Rules for using mmu_spte_update:
* Update the state bits, it means the mapped pfn is not changged.
*/
static void mmu_spte_update(u64 *sptep, u64 new_spte)
{
u64 mask, old_spte = *sptep;
WARN_ON(!is_rmap_spte(new_spte));
if (!is_shadow_present_pte(old_spte))
return mmu_spte_set(sptep, new_spte);
new_spte |= old_spte & shadow_dirty_mask;
mask = shadow_accessed_mask;
@ -325,6 +343,42 @@ static void update_spte(u64 *sptep, u64 new_spte)
kvm_set_pfn_dirty(spte_to_pfn(old_spte));
}
/*
* Rules for using mmu_spte_clear_track_bits:
* It sets the sptep from present to nonpresent, and track the
* state bits, it is used to clear the last level sptep.
*/
static int mmu_spte_clear_track_bits(u64 *sptep)
{
pfn_t pfn;
u64 old_spte = *sptep;
if (!spte_has_volatile_bits(old_spte))
__set_spte(sptep, 0ull);
else
old_spte = __xchg_spte(sptep, 0ull);
if (!is_rmap_spte(old_spte))
return 0;
pfn = spte_to_pfn(old_spte);
if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
kvm_set_pfn_accessed(pfn);
if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask))
kvm_set_pfn_dirty(pfn);
return 1;
}
/*
* Rules for using mmu_spte_clear_no_track:
* Directly clear spte without caring the state bits of sptep,
* it is used to set the upper level spte.
*/
static void mmu_spte_clear_no_track(u64 *sptep)
{
__set_spte(sptep, 0ull);
}
static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
struct kmem_cache *base_cache, int min)
{
@ -746,30 +800,9 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
pte_list_remove(spte, rmapp);
}
static int set_spte_track_bits(u64 *sptep, u64 new_spte)
{
pfn_t pfn;
u64 old_spte = *sptep;
if (!spte_has_volatile_bits(old_spte))
__set_spte(sptep, new_spte);
else
old_spte = __xchg_spte(sptep, new_spte);
if (!is_rmap_spte(old_spte))
return 0;
pfn = spte_to_pfn(old_spte);
if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
kvm_set_pfn_accessed(pfn);
if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask))
kvm_set_pfn_dirty(pfn);
return 1;
}
static void drop_spte(struct kvm *kvm, u64 *sptep)
{
if (set_spte_track_bits(sptep, 0ull))
if (mmu_spte_clear_track_bits(sptep))
rmap_remove(kvm, sptep);
}
@ -787,7 +820,7 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn)
BUG_ON(!(*spte & PT_PRESENT_MASK));
rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
if (is_writable_pte(*spte)) {
update_spte(spte, *spte & ~PT_WRITABLE_MASK);
mmu_spte_update(spte, *spte & ~PT_WRITABLE_MASK);
write_protected = 1;
}
spte = rmap_next(kvm, rmapp, spte);
@ -856,7 +889,8 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
new_spte &= ~PT_WRITABLE_MASK;
new_spte &= ~SPTE_HOST_WRITEABLE;
new_spte &= ~shadow_accessed_mask;
set_spte_track_bits(spte, new_spte);
mmu_spte_clear_track_bits(spte);
mmu_spte_set(spte, new_spte);
spte = rmap_next(kvm, rmapp, spte);
}
}
@ -1077,7 +1111,7 @@ static void drop_parent_pte(struct kvm_mmu_page *sp,
u64 *parent_pte)
{
mmu_page_remove_parent_pte(sp, parent_pte);
__set_spte(parent_pte, 0ull);
mmu_spte_clear_no_track(parent_pte);
}
static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
@ -1525,7 +1559,7 @@ static void link_shadow_page(u64 *sptep, struct kvm_mmu_page *sp)
spte = __pa(sp->spt)
| PT_PRESENT_MASK | PT_ACCESSED_MASK
| PT_WRITABLE_MASK | PT_USER_MASK;
__set_spte(sptep, spte);
mmu_spte_set(sptep, spte);
}
static void drop_large_spte(struct kvm_vcpu *vcpu, u64 *sptep)
@ -1992,7 +2026,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
mark_page_dirty(vcpu->kvm, gfn);
set_pte:
update_spte(sptep, spte);
mmu_spte_update(sptep, spte);
/*
* If we overwrite a writable spte with a read-only one we
* should flush remote TLBs. Otherwise rmap_write_protect
@ -2198,11 +2232,11 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
return -ENOMEM;
}
__set_spte(iterator.sptep,
__pa(sp->spt)
| PT_PRESENT_MASK | PT_WRITABLE_MASK
| shadow_user_mask | shadow_x_mask
| shadow_accessed_mask);
mmu_spte_set(iterator.sptep,
__pa(sp->spt)
| PT_PRESENT_MASK | PT_WRITABLE_MASK
| shadow_user_mask | shadow_x_mask
| shadow_accessed_mask);
}
}
return emulate;
@ -3439,7 +3473,8 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
/* avoid RMW */
if (is_writable_pte(pt[i]))
update_spte(&pt[i], pt[i] & ~PT_WRITABLE_MASK);
mmu_spte_update(&pt[i],
pt[i] & ~PT_WRITABLE_MASK);
}
}
kvm_flush_remote_tlbs(kvm);