Thread (42 messages) 42 messages, 3 authors, 2021-07-21

Re: [PATCH 12/14] KVM: arm64: Refactor pkvm_pgtable locking

From: Fuad Tabba <hidden>
Date: 2021-07-21 08:42:31
Also in: kvmarm, lkml

Hi Quentin,

On Mon, Jul 19, 2021 at 11:48 AM Quentin Perret [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Refactor the hypervisor stage-1 locking in nVHE protected mode to expose
a new pkvm_create_mappings_locked() function. This will be used in later
patches to allow walking and changing the hypervisor stage-1 without
releasing the lock.

Signed-off-by: Quentin Perret <redacted>
---
 arch/arm64/kvm/hyp/include/nvhe/mm.h |  1 +
 arch/arm64/kvm/hyp/nvhe/mm.c         | 16 ++++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kvm/hyp/include/nvhe/mm.h b/arch/arm64/kvm/hyp/include/nvhe/mm.h
index 8ec3a5a7744b..c76d7136ed9b 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mm.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mm.h
@@ -23,6 +23,7 @@ int hyp_map_vectors(void);
 int hyp_back_vmemmap(phys_addr_t phys, unsigned long size, phys_addr_t back);
 int pkvm_cpu_set_vector(enum arm64_hyp_spectre_vector slot);
 int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot);
+int pkvm_create_mappings_locked(void *from, void *to, enum kvm_pgtable_prot prot);
 int __pkvm_create_mappings(unsigned long start, unsigned long size,
                           unsigned long phys, enum kvm_pgtable_prot prot);
 unsigned long __pkvm_create_private_mapping(phys_addr_t phys, size_t size,
The locking logic seems to be consistent, with pkvm_create_mappings()
holding the lock for the whole duration of the operation rather than
per-iteration.

It would be nice though to document which lock should be held for the
_locked versions.

Thanks,
/fuad



quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kvm/hyp/nvhe/mm.c b/arch/arm64/kvm/hyp/nvhe/mm.c
index a8efdf0f9003..dde22e2a322a 100644
--- a/arch/arm64/kvm/hyp/nvhe/mm.c
+++ b/arch/arm64/kvm/hyp/nvhe/mm.c
@@ -67,7 +67,7 @@ unsigned long __pkvm_create_private_mapping(phys_addr_t phys, size_t size,
        return addr;
 }

-int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
+int pkvm_create_mappings_locked(void *from, void *to, enum kvm_pgtable_prot prot)
 {
        unsigned long start = (unsigned long)from;
        unsigned long end = (unsigned long)to;
@@ -81,7 +81,8 @@ int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
                int err;

                phys = hyp_virt_to_phys((void *)virt_addr);
-               err = __pkvm_create_mappings(virt_addr, PAGE_SIZE, phys, prot);
+               err = kvm_pgtable_hyp_map(&pkvm_pgtable, virt_addr, PAGE_SIZE,
+                                         phys, prot);
                if (err)
                        return err;
        }
@@ -89,6 +90,17 @@ int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
        return 0;
 }

+int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
+{
+       int ret;
+
+       hyp_spin_lock(&pkvm_pgd_lock);
+       ret = pkvm_create_mappings_locked(from, to, prot);
+       hyp_spin_unlock(&pkvm_pgd_lock);
+
+       return ret;
+}
+
 int hyp_back_vmemmap(phys_addr_t phys, unsigned long size, phys_addr_t back)
 {
        unsigned long start, end;
--
2.32.0.402.g57bb445576-goog
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