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authorSean Christopherson <seanjc@google.com>2022-10-13 21:12:29 +0000
committerDavid Woodhouse <dwmw@amazon.co.uk>2022-11-30 19:25:24 +0000
commit9f87791d686d85614584438d4f249eb32ef7964c (patch)
treec2c4a01fd11883c843242ad0a3035fd7754809fa /virt
parent0318f207d1c2e297d1ec1c6e145bb8bd053236f9 (diff)
KVM: Drop KVM's API to allow temporarily unmapping gfn=>pfn cache
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@infradead.org Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/pfncache.c44
1 files changed, 16 insertions, 28 deletions
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 015c5d16948a..5b2512793691 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -333,33 +333,6 @@ out_unlock:
}
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 → 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)
{
@@ -405,6 +378,8 @@ 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) {
/*
@@ -414,13 +389,26 @@ 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 needs to be redone every
+ * time as mmu_notifier protection is lost when the cache is
+ * removed from the VM's gpc_list.
+ */
+ 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);