On Sun, Nov 13, 2022 at 05:05:08PM +0000, Shivam Kumar wrote:
> Exit to userspace whenever the dirty quota is exhausted (i.e. dirty count
> equals/exceeds dirty quota) to request more dirty quota.
>
> Suggested-by: Shaju Abraham <shaju.abraham@xxxxxxxxxxx>
> Suggested-by: Manish Mishra <manish.mishra@xxxxxxxxxxx>
> Co-developed-by: Anurag Madnawat <anurag.madnawat@xxxxxxxxxxx>
> Signed-off-by: Anurag Madnawat <anurag.madnawat@xxxxxxxxxxx>
> Signed-off-by: Shivam Kumar <shivam.kumar1@xxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu/spte.c | 4 ++--
> arch/x86/kvm/vmx/vmx.c | 3 +++
> arch/x86/kvm/x86.c | 28 ++++++++++++++++++++++++++++
> 3 files changed, 33 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
> index 2e08b2a45361..c0ed35abbf2d 100644
> --- a/arch/x86/kvm/mmu/spte.c
> +++ b/arch/x86/kvm/mmu/spte.c
> @@ -228,9 +228,9 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> "spte = 0x%llx, level = %d, rsvd bits = 0x%llx", spte, level,
> get_rsvd_bits(&vcpu->arch.mmu->shadow_zero_check, spte, level));
>
> - if ((spte & PT_WRITABLE_MASK) && kvm_slot_dirty_track_enabled(slot)) {
> + if (spte & PT_WRITABLE_MASK) {
> /* Enforced by kvm_mmu_hugepage_adjust. */
> - WARN_ON(level > PG_LEVEL_4K);
> + WARN_ON(level > PG_LEVEL_4K && kvm_slot_dirty_track_enabled(slot));
> mark_page_dirty_in_slot(vcpu->kvm, slot, gfn);
> }
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 63247c57c72c..cc130999eddf 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -5745,6 +5745,9 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
> */
> if (__xfer_to_guest_mode_work_pending())
> return 1;
> +
> + if (kvm_test_request(KVM_REQ_DIRTY_QUOTA_EXIT, vcpu))
> + return 1;
Any reason for this check? Is this quota related to the invalid
guest state? Sorry if I missed anything here.
> }
>
> return 1;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index ecea83f0da49..1a960fbb51f4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10494,6 +10494,30 @@ void __kvm_request_immediate_exit(struct kvm_vcpu *vcpu)
> }
> EXPORT_SYMBOL_GPL(__kvm_request_immediate_exit);
>
> +static inline bool kvm_check_dirty_quota_request(struct kvm_vcpu *vcpu)
> +{
> +#ifdef CONFIG_HAVE_KVM_DIRTY_QUOTA
> + struct kvm_run *run;
> +
> + if (kvm_check_request(KVM_REQ_DIRTY_QUOTA_EXIT, vcpu)) {
> + run = vcpu->run;
> + run->exit_reason = KVM_EXIT_DIRTY_QUOTA_EXHAUSTED;
> + run->dirty_quota_exit.count = vcpu->stat.generic.pages_dirtied;
> + run->dirty_quota_exit.quota = READ_ONCE(run->dirty_quota);
> +
> + /*
> + * Re-check the quota and exit if and only if the vCPU still
> + * exceeds its quota. If userspace increases (or disables
> + * entirely) the quota, then no exit is required as KVM is
> + * still honoring its ABI, e.g. userspace won't even be aware
> + * that KVM temporarily detected an exhausted quota.
> + */
> + return run->dirty_quota_exit.count >= run->dirty_quota_exit.quota;
Would it be better to check before updating the vcpu->run?
