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Message-Id: <20220830195216.964988-1-oliver.upton@linux.dev>
Date: Tue, 30 Aug 2022 19:52:15 +0000
From: Oliver Upton <oliver.upton@...ux.dev>
To: Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Oliver Upton <oliver.upton@...ux.dev>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
kvm@...r.kernel.org, Quentin Perret <qperret@...gle.com>,
Ricardo Koller <ricarkol@...gle.com>,
Reiji Watanabe <reijiw@...gle.com>,
David Matlack <dmatlack@...gle.com>,
Ben Gardon <bgardon@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Gavin Shan <gshan@...hat.com>, Peter Xu <peterx@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH 14/14] KVM: arm64: Handle stage-2 faults in parallel
The stage-2 map walker has been made parallel-aware, and as such can be
called while only holding the read side of the MMU lock. Rip out the
conditional locking in user_mem_abort() and instead grab the read lock.
Continue to take the write lock from other callsites to
kvm_pgtable_stage2_map().
Signed-off-by: Oliver Upton <oliver.upton@...ux.dev>
---
arch/arm64/include/asm/kvm_pgtable.h | 4 +++-
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 2 +-
arch/arm64/kvm/hyp/pgtable.c | 3 ++-
arch/arm64/kvm/mmu.c | 31 ++++++---------------------
4 files changed, 13 insertions(+), 27 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 7d2de0a98ccb..dc839db86a1a 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -355,6 +355,8 @@ void kvm_pgtable_stage2_free_removed(void *pgtable, u32 level, void *arg);
* @prot: Permissions and attributes for the mapping.
* @mc: Cache of pre-allocated and zeroed memory from which to allocate
* page-table pages.
+ * @shared: true if multiple software walkers could be traversing the tables
+ * in parallel
*
* The offset of @addr within a page is ignored, @size is rounded-up to
* the next page boundary and @phys is rounded-down to the previous page
@@ -376,7 +378,7 @@ void kvm_pgtable_stage2_free_removed(void *pgtable, u32 level, void *arg);
*/
int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
u64 phys, enum kvm_pgtable_prot prot,
- void *mc);
+ void *mc, bool shared);
/**
* kvm_pgtable_stage2_set_owner() - Unmap and annotate pages in the IPA space to
diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 61cf223e0796..924d028af447 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -252,7 +252,7 @@ static inline int __host_stage2_idmap(u64 start, u64 end,
enum kvm_pgtable_prot prot)
{
return kvm_pgtable_stage2_map(&host_kvm.pgt, start, end - start, start,
- prot, &host_s2_pool);
+ prot, &host_s2_pool, false);
}
/*
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 92e230e7bf3a..52ecaaa84b22 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -944,7 +944,7 @@ static int stage2_map_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep, kvm_
int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
u64 phys, enum kvm_pgtable_prot prot,
- void *mc)
+ void *mc, bool shared)
{
int ret;
struct stage2_map_data map_data = {
@@ -953,6 +953,7 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
.memcache = mc,
.mm_ops = pgt->mm_ops,
.force_pte = pgt->force_pte_cb && pgt->force_pte_cb(addr, addr + size, prot),
+ .shared = shared,
};
struct kvm_pgtable_walker walker = {
.cb = stage2_map_walker,
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 265951c05879..a73adc35cf41 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -840,7 +840,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
write_lock(&kvm->mmu_lock);
ret = kvm_pgtable_stage2_map(pgt, addr, PAGE_SIZE, pa, prot,
- &cache);
+ &cache, false);
write_unlock(&kvm->mmu_lock);
if (ret)
break;
@@ -1135,7 +1135,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
gfn_t gfn;
kvm_pfn_t pfn;
bool logging_active = memslot_is_logging(memslot);
- bool use_read_lock = false;
unsigned long fault_level = kvm_vcpu_trap_get_fault_level(vcpu);
unsigned long vma_pagesize, fault_granule;
enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
@@ -1170,8 +1169,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (logging_active) {
force_pte = true;
vma_shift = PAGE_SHIFT;
- use_read_lock = (fault_status == FSC_PERM && write_fault &&
- fault_granule == PAGE_SIZE);
} else {
vma_shift = get_vma_page_shift(vma, hva);
}
@@ -1270,15 +1267,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (exec_fault && device)
return -ENOEXEC;
- /*
- * To reduce MMU contentions and enhance concurrency during dirty
- * logging dirty logging, only acquire read lock for permission
- * relaxation.
- */
- if (use_read_lock)
- read_lock(&kvm->mmu_lock);
- else
- write_lock(&kvm->mmu_lock);
+ read_lock(&kvm->mmu_lock);
pgt = vcpu->arch.hw_mmu->pgt;
if (mmu_invalidate_retry(kvm, mmu_seq))
goto out_unlock;
@@ -1322,15 +1311,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
* permissions only if vma_pagesize equals fault_granule. Otherwise,
* kvm_pgtable_stage2_map() should be called to change block size.
*/
- if (fault_status == FSC_PERM && vma_pagesize == fault_granule) {
+ if (fault_status == FSC_PERM && vma_pagesize == fault_granule)
ret = kvm_pgtable_stage2_relax_perms(pgt, fault_ipa, prot);
- } else {
- WARN_ONCE(use_read_lock, "Attempted stage-2 map outside of write lock\n");
-
+ else
ret = kvm_pgtable_stage2_map(pgt, fault_ipa, vma_pagesize,
__pfn_to_phys(pfn), prot,
- memcache);
- }
+ memcache, true);
/* Mark the page dirty only if the fault is handled successfully */
if (writable && !ret) {
@@ -1339,10 +1325,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
}
out_unlock:
- if (use_read_lock)
- read_unlock(&kvm->mmu_lock);
- else
- write_unlock(&kvm->mmu_lock);
+ read_unlock(&kvm->mmu_lock);
kvm_set_pfn_accessed(pfn);
kvm_release_pfn_clean(pfn);
return ret != -EAGAIN ? ret : 0;
@@ -1548,7 +1531,7 @@ bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
*/
kvm_pgtable_stage2_map(kvm->arch.mmu.pgt, range->start << PAGE_SHIFT,
PAGE_SIZE, __pfn_to_phys(pfn),
- KVM_PGTABLE_PROT_R, NULL);
+ KVM_PGTABLE_PROT_R, NULL, false);
return false;
}
--
2.37.2.672.g94769d06f0-goog
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