From: Sean Christopherson <seanjc@xxxxxxxxxx>
Drop kvm_gpc_unmap() as it has no users and unclear requirements. The
API was added as part of the original gfn_to_pfn_cache support, but its
sole usage[*] was never merged. Fold the guts of kvm_gpc_unmap() into
the deactivate path and drop the API. Omit acquiring refresh_lock as
as concurrent calls to kvm_gpc_deactivate() are not allowed (this is
not enforced, e.g. via lockdep. due to it being called during vCPU
destruction).
If/when temporary unmapping makes a comeback, the desirable behavior is
likely to restrict temporary unmapping to vCPU-exclusive mappings and
require the vcpu->mutex be held to serialize unmap. Use of the
refresh_lock to protect unmapping was somewhat specuatively added by
commit 93984f19e7bc ("KVM: Fully serialize gfn=>pfn cache refresh via
mutex") to guard against concurrent unmaps, but the primary use case of
the temporary unmap, nested virtualization[*], doesn't actually need or
want concurrent unmaps.
[*] https://lore.kernel.org/all/20211210163625.2886-7-dwmw2@xxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-Id: <20221013211234.1318131-12-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
include/linux/kvm_host.h | 12 -----------
virt/kvm/pfncache.c | 44 +++++++++++++++-------------------------
2 files changed, 16 insertions(+), 40 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d4a49c89bc08..3847b721e753 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1314,18 +1314,6 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa);
*/
int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa);
-/**
- * kvm_gpc_unmap - temporarily unmap a gfn_to_pfn_cache.
- *
- * @kvm: pointer to kvm instance.
- * @gpc: struct gfn_to_pfn_cache object.
- *
- * This unmaps the referenced page. The cache is left in the invalid state
- * but at least the mapping from GPA to userspace HVA will remain cached
- * and can be reused on a subsequent refresh.
- */
-void kvm_gpc_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc);
-
/**
* kvm_gpc_deactivate - deactivate and unlink a gfn_to_pfn_cache.
*
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index e4ebea75dca9..62429b2a6389 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -335,33 +335,6 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa)
}
EXPORT_SYMBOL_GPL(kvm_gpc_refresh);
-void kvm_gpc_unmap(struct kvm *kvm, struct gfn_to_pfn_cache *gpc)
-{
- void *old_khva;
- kvm_pfn_t old_pfn;
-
- mutex_lock(&gpc->refresh_lock);
- write_lock_irq(&gpc->lock);
-
- gpc->valid = false;
-
- old_khva = gpc->khva - offset_in_page(gpc->khva);
- old_pfn = gpc->pfn;
-
- /*
- * We can leave the GPA â?? uHVA map cache intact but the PFN
- * lookup will need to be redone even for the same page.
- */
- gpc->khva = NULL;
- gpc->pfn = KVM_PFN_ERR_FAULT;
-
- write_unlock_irq(&gpc->lock);
- mutex_unlock(&gpc->refresh_lock);
-
- gpc_unmap_khva(old_pfn, old_khva);
-}
-EXPORT_SYMBOL_GPL(kvm_gpc_unmap);
-
void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm,
struct kvm_vcpu *vcpu, enum pfn_cache_usage usage)
{
@@ -407,6 +380,8 @@ EXPORT_SYMBOL_GPL(kvm_gpc_activate);
void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)
{
struct kvm *kvm = gpc->kvm;
+ kvm_pfn_t old_pfn;
+ void *old_khva;
if (gpc->active) {
/*
@@ -416,13 +391,26 @@ void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)
*/
write_lock_irq(&gpc->lock);
gpc->active = false;
+ gpc->valid = false;
+
+ /*
+ * Leave the GPA => uHVA cache intact, it's protected by the
+ * memslot generation. The PFN lookup however will have to be
+ * redone after the cache is removed from the VM's gpc_list,
+ * as that loses mmu_notifier protection.
+ */
+ old_khva = gpc->khva - offset_in_page(gpc->khva);
+ gpc->khva = NULL;
+
+ old_pfn = gpc->pfn;
+ gpc->pfn = KVM_PFN_ERR_FAULT;
write_unlock_irq(&gpc->lock);
spin_lock(&kvm->gpc_lock);
list_del(&gpc->list);
spin_unlock(&kvm->gpc_lock);
- kvm_gpc_unmap(kvm, gpc);
+ gpc_unmap_khva(old_pfn, old_khva);
}
}
EXPORT_SYMBOL_GPL(kvm_gpc_deactivate);
--
2.31.1
