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ANDROID: KVM: arm64: Avoid switching to guest context if guest is already loaded

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Typically, TLB invalidation of guest stage-2 mappings using nVHE is
performed by a hypercall originating from the host. For the invalidation
instruction to be effective, therefore, __tlb_switch_to_{guest,host}()
swizzle the active stage-2 context around the TLBI instruction.

With guest-to-host memory sharing hypercalls originating from the guest
under pKVM, there is no need to change the context when invalidating the
TLB and restoring the host context is, in fact, harmful.

Check the currently running vCPU in __tlb_switch_to_{guest,host}() and
avoid switching the context if a vCPU is already loaded.

Signed-off-by: Will Deacon <will@kernel.org>
Bug: 209580772
Change-Id: I4cfb36f0f88a2d50d50ea85a0d84e3e8191152a3
Signed-off-by: Will Deacon <willdeacon@google.com>
This commit is contained in:
Will Deacon
2021-11-08 17:27:41 +00:00
committed by Will Deacon
parent 94391c57a5
commit ecf2308ee8
1 changed files with 17 additions and 0 deletions
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17
arch/arm64/kvm/hyp/nvhe/tlb.c
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@@ -17,6 +17,17 @@ struct tlb_inv_context {
static void __tlb_switch_to_guest(struct kvm_s2_mmu *mmu,
struct tlb_inv_context *cxt)
{
struct kvm_cpu_context *host_ctxt;
struct kvm_vcpu *vcpu;
host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
vcpu = host_ctxt->__hyp_running_vcpu;
if (vcpu) {
WARN_ON(vcpu->arch.hw_mmu->vmid.vmid != mmu->vmid.vmid);
return;
}
if (cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT)) {
u64 val;
@@ -45,6 +56,12 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu *mmu,
static void __tlb_switch_to_host(struct tlb_inv_context *cxt)
{
struct kvm_cpu_context *host_ctxt;
host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
if (host_ctxt->__hyp_running_vcpu)
return;
__load_host_stage2();
if (cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT)) {