[PATCH v2 16/22] powerpc/kvm/book3s: Avoid using rmap to protect parallel page table update.

From: Aneesh Kumar K.V
Date: Wed Mar 18 2020 - 23:57:43 EST


We now depend on kvm->mmu_lock

Cc: Alexey Kardashevskiy <aik@xxxxxxxxx>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
arch/powerpc/kvm/book3s_64_vio_hv.c | 38 +++++++----------------------
1 file changed, 9 insertions(+), 29 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
index 8a6bf12d2e88..2176d0d225d2 100644
--- a/arch/powerpc/kvm/book3s_64_vio_hv.c
+++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
@@ -75,8 +75,8 @@ struct kvmppc_spapr_tce_table *kvmppc_find_table(struct kvm *kvm,
EXPORT_SYMBOL_GPL(kvmppc_find_table);

#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
-static long kvmppc_rm_tce_to_ua(struct kvm *kvm, unsigned long tce,
- unsigned long *ua, unsigned long **prmap)
+static long kvmppc_rm_tce_to_ua(struct kvm *kvm,
+ unsigned long tce, unsigned long *ua)
{
unsigned long gfn = tce >> PAGE_SHIFT;
struct kvm_memory_slot *memslot;
@@ -88,9 +88,6 @@ static long kvmppc_rm_tce_to_ua(struct kvm *kvm, unsigned long tce,
*ua = __gfn_to_hva_memslot(memslot, gfn) |
(tce & ~(PAGE_MASK | TCE_PCI_READ | TCE_PCI_WRITE));

- if (prmap)
- *prmap = &memslot->arch.rmap[gfn - memslot->base_gfn];
-
return 0;
}

@@ -117,7 +114,7 @@ static long kvmppc_rm_tce_validate(struct kvmppc_spapr_tce_table *stt,
if (iommu_tce_check_gpa(stt->page_shift, gpa))
return H_PARAMETER;

- if (kvmppc_rm_tce_to_ua(stt->kvm, tce, &ua, NULL))
+ if (kvmppc_rm_tce_to_ua(stt->kvm, tce, &ua))
return H_TOO_HARD;

list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
@@ -412,7 +409,7 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
return ret;

dir = iommu_tce_direction(tce);
- if ((dir != DMA_NONE) && kvmppc_rm_tce_to_ua(vcpu->kvm, tce, &ua, NULL))
+ if ((dir != DMA_NONE) && kvmppc_rm_tce_to_ua(vcpu->kvm, tce, &ua))
return H_PARAMETER;

entry = ioba >> stt->page_shift;
@@ -489,7 +486,6 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
struct kvmppc_spapr_tce_table *stt;
long i, ret = H_SUCCESS;
unsigned long tces, entry, ua = 0;
- unsigned long *rmap = NULL;
unsigned long mmu_seq;
bool prereg = false;
struct kvmppc_spapr_tce_iommu_table *stit;
@@ -531,7 +527,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
*/
struct mm_iommu_table_group_mem_t *mem;

- if (kvmppc_rm_tce_to_ua(vcpu->kvm, tce_list, &ua, NULL))
+ if (kvmppc_rm_tce_to_ua(vcpu->kvm, tce_list, &ua))
return H_TOO_HARD;

mem = mm_iommu_lookup_rm(vcpu->kvm->mm, ua, IOMMU_PAGE_SIZE_4K);
@@ -547,23 +543,9 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
* We do not require memory to be preregistered in this case
* so lock rmap and do __find_linux_pte_or_hugepte().
*/
- if (kvmppc_rm_tce_to_ua(vcpu->kvm, tce_list, &ua, &rmap))
- return H_TOO_HARD;
-
- rmap = (void *) vmalloc_to_phys(rmap);
- if (WARN_ON_ONCE_RM(!rmap))
+ if (kvmppc_rm_tce_to_ua(vcpu->kvm, tce_list, &ua))
return H_TOO_HARD;

- /*
- * Synchronize with the MMU notifier callbacks in
- * book3s_64_mmu_hv.c (kvm_unmap_hva_range_hv etc.).
- * While we have the rmap lock, code running on other CPUs
- * cannot finish unmapping the host real page that backs
- * this guest real page, so we are OK to access the host
- * real page.
- */
- lock_rmap(rmap);
-
arch_spin_lock(&kvm->mmu_lock.rlock.raw_lock);
if (kvmppc_rm_ua_to_hpa(vcpu, mmu_seq, ua, &tces)) {
ret = H_TOO_HARD;
@@ -583,7 +565,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
unsigned long tce = be64_to_cpu(((u64 *)tces)[i]);

ua = 0;
- if (kvmppc_rm_tce_to_ua(vcpu->kvm, tce, &ua, NULL)) {
+ if (kvmppc_rm_tce_to_ua(vcpu->kvm, tce, &ua)) {
ret = H_PARAMETER;
goto invalidate_exit;
}
@@ -608,10 +590,8 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
iommu_tce_kill_rm(stit->tbl, entry, npages);

unlock_exit:
- if (rmap)
- unlock_rmap(rmap);
-
- arch_spin_unlock(&kvm->mmu_lock.rlock.raw_lock);
+ if (!prereg)
+ arch_spin_unlock(&kvm->mmu_lock.rlock.raw_lock);
return ret;
}

--
2.24.1