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| author | Junaid Shahid <junaids@google.com> | 2018-06-28 00:59:06 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-08-06 18:58:51 +0300 |
| commit | 7c390d350f8b677df3236afef4ced80dba6c3201 (patch) | |
| tree | 8853310526d28d88ed66aace7e035f3a09791bc0 /arch/x86/kvm/x86.c | |
| parent | 578e1c4db22135d91bad6c79585c4d19252b8d81 (diff) | |
| download | linux-7c390d350f8b677df3236afef4ced80dba6c3201.tar.xz | |
kvm: x86: Add fast CR3 switch code path
When using shadow paging, a CR3 switch in the guest results in a VM Exit.
In the common case, that VM exit doesn't require much processing by KVM.
However, it does acquire the MMU lock, which can start showing signs of
contention under some workloads even on a 2 VCPU VM when the guest is
using KPTI. Therefore, we add a fast path that avoids acquiring the MMU
lock in the most common cases e.g. when switching back and forth between
the kernel and user mode CR3s used by KPTI with no guest page table
changes in between.
For now, this fast path is implemented only for 64-bit guests and hosts
to avoid the handling of PDPTEs, but it can be extended later to 32-bit
guests and/or hosts as well.
Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1b14c4a654c3..5a1e4f79398f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -867,9 +867,10 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) return 1; + kvm_mmu_new_cr3(vcpu, cr3); vcpu->arch.cr3 = cr3; __set_bit(VCPU_EXREG_CR3, (ulong *)&vcpu->arch.regs_avail); - kvm_mmu_new_cr3(vcpu); + return 0; } EXPORT_SYMBOL_GPL(kvm_set_cr3); |