path: root/arch/x86/include/asm
diff options
authorSean Christopherson <>2019-02-05 13:01:22 -0800
committerPaolo Bonzini <>2019-02-20 22:48:39 +0100
commita592a3b8fc62af25a6e76aebde97a5d5f6f13e0f (patch)
treec01ed8c513f9a5df6d3665cf57b85032b663babd /arch/x86/include/asm
parent4e103134b862314dc2f2f18f2fb0ab972adc3f5f (diff)
Revert "KVM: MMU: document fast invalidate all pages"
Remove x86 KVM's fast invalidate mechanism, i.e. revert all patches from the original series[1]. Though not explicitly stated, for all intents and purposes the fast invalidate mechanism was added to speed up the scenario where removing a memslot, e.g. as part of accessing reading PCI ROM, caused KVM to flush all shadow entries[1]. Now that the memslot case flushes only shadow entries belonging to the memslot, i.e. doesn't use the fast invalidate mechanism, the only remaining usage of the mechanism are when the VM is being destroyed and when the MMIO generation rolls over. When a VM is being destroyed, either there are no active vcpus, i.e. there's no lock contention, or the VM has ungracefully terminated, in which case we want to reclaim its pages as quickly as possible, i.e. not release the MMU lock if there are still CPUs executing in the VM. The MMIO generation scenario is almost literally a one-in-a-million occurrence, i.e. is not a performance sensitive scenario. Given that lock-breaking is not desirable (VM teardown) or irrelevant (MMIO generation overflow), remove the fast invalidate mechanism to simplify the code (a small amount) and to discourage future code from zapping all pages as using such a big hammer should be a last restort. This reverts commit f6f8adeef542a18b1cb26a0b772c9781a10bb477. [1] Cc: Xiao Guangrong <> Signed-off-by: Sean Christopherson <> Signed-off-by: Paolo Bonzini <>
Diffstat (limited to 'arch/x86/include/asm')
1 files changed, 0 insertions, 3 deletions
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c4758e1a8843..69daa57b08a7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -333,10 +333,7 @@ struct kvm_mmu_page {
int root_count; /* Currently serving as active root */
unsigned int unsync_children;
struct kvm_rmap_head parent_ptes; /* rmap pointers to parent sptes */
- /* The page is obsolete if mmu_valid_gen != kvm->arch.mmu_valid_gen. */
unsigned long mmu_valid_gen;
DECLARE_BITMAP(unsync_child_bitmap, 512);
#ifdef CONFIG_X86_32