Re: [PATCH v10 05/39] KVM: x86: hyper-v: Handle HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls gently

Sean Christopherson
2022-09-21T17:01:30Z

On Wed, Sep 21, 2022, Vitaly Kuznetsov wrote:
> void kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
> {
> struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
> struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
> + u64 entries[KVM_HV_TLB_FLUSH_FIFO_SIZE];
> + int i, j, count;
> + gva_t gva;
>
> - kvm_vcpu_flush_tlb_guest(vcpu);
> -
> - if (!hv_vcpu)
> + if (!tdp_enabled || !hv_vcpu) {
> + kvm_vcpu_flush_tlb_guest(vcpu);
> return;
> + }
>
> tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo;
>
> + count = kfifo_out(&tlb_flush_fifo->entries, entries, KVM_HV_TLB_FLUSH_FIFO_SIZE);
> +
> + for (i = 0; i < count; i++) {
> + if (entries[i] == KVM_HV_TLB_FLUSHALL_ENTRY)
> + goto out_flush_all;
> +
> + /*
> + * Lower 12 bits of 'address' encode the number of additional
> + * pages to flush.
> + */
> + gva = entries[i] & PAGE_MASK;
> + for (j = 0; j < (entries[i] & ~PAGE_MASK) + 1; j++)
> + static_call(kvm_x86_flush_tlb_gva)(vcpu, gva + j * PAGE_SIZE);
> +
> + ++vcpu->stat.tlb_flush;
> + }
> + return;
> +
> +out_flush_all:
> + kvm_vcpu_flush_tlb_guest(vcpu);
> kfifo_reset_out(&tlb_flush_fifo->entries);
> }

If kvm_vcpu_flush_tlb_guest() is done as a fallback, then this can use -ENOSPC,
which again I like from a documentation perspective.

out_flush_all:
kfifo_reset_out(&tlb_flush_fifo->entries);
return -ENOSPC;