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Move VMX vpid allocation to fix vpid leak in vmm.
On Sun, Sep 01, 2024 at 09:46:16PM -0400, Dave Voutila wrote:
> I noticed this while Hans-Joerg was working on SEV support for
> vmm(4). Since vpid allocation is in the reset register ioctl handler,
> and we don't free any previous vpid, a program on an Intel host that
> keeps resetting a vcpu via VMM_IOC_RESETCPU will exhaust vpids.
>
> Instead of a check & free dance, this just moves the allocation to the
> vcpu initialization since vmm frees vpids/asids in vcpu de-init. (The
> SEV changes moved the SVM ASID stuff similarly.)
>
> It also removes the DPRINTF (also on the SVM side) since the allocation
> function already has a printf on failure.
>
> Plus, since we're de-coupling allocation from configuration, the VMCS
> reload can be avoided, making this a net-negative diff.
>
> ok?
>
Not sure if that matters, but previously vmm_init_vpx()'s ENOMEM was
always mapped to EINVAL. Now there's a bit of an asymmetry between
vcpu_init_vmx() and vcpu_init_svm() in that regard.
>
> diffstat refs/heads/master refs/heads/vpid-leak
> M sys/arch/amd64/amd64/vmm_machdep.c | 7+ 21-
>
> 1 file changed, 7 insertions(+), 21 deletions(-)
>
> diff refs/heads/master refs/heads/vpid-leak
> commit - 24056440d1d6e8d3aa8785990526387386042fb4
> commit + a01d423d1b92501a0e6b5cc4b9fe22a9e3983795
> blob - c84fbb3273c799116e4628a1097db4eb9f135955
> blob + a472790c5d18da3cc8c7954a2c5006b745009c53
> --- sys/arch/amd64/amd64/vmm_machdep.c
> +++ sys/arch/amd64/amd64/vmm_machdep.c
> @@ -2253,7 +2253,7 @@ vcpu_reset_regs_vmx(struct vcpu *vcpu, struct vcpu_reg
> uint32_t pinbased, procbased, procbased2, exit, entry;
> uint32_t want1, want0;
> uint64_t ctrlval, cr3, msr_misc_enable;
> - uint16_t ctrl, vpid;
> + uint16_t ctrl;
> struct vmx_msr_store *msr_store;
>
> rw_assert_wrlock(&vcpu->vc_lock);
> @@ -2516,30 +2516,12 @@ vcpu_reset_regs_vmx(struct vcpu *vcpu, struct vcpu_reg
> IA32_VMX_ACTIVATE_SECONDARY_CONTROLS, 1)) {
> if (vcpu_vmx_check_cap(vcpu, IA32_VMX_PROCBASED2_CTLS,
> IA32_VMX_ENABLE_VPID, 1)) {
> -
> - /* We may sleep during allocation, so reload VMCS. */
> - vcpu->vc_last_pcpu = curcpu();
> - ret = vmm_alloc_vpid(&vpid);
> - if (vcpu_reload_vmcs_vmx(vcpu)) {
> - printf("%s: failed to reload vmcs\n", __func__);
> - ret = EINVAL;
> - goto exit;
> - }
> - if (ret) {
> - DPRINTF("%s: could not allocate VPID\n",
> - __func__);
> - ret = EINVAL;
> - goto exit;
> - }
> -
> - if (vmwrite(VMCS_GUEST_VPID, vpid)) {
> + if (vmwrite(VMCS_GUEST_VPID, vcpu->vc_vpid)) {
> DPRINTF("%s: error setting guest VPID\n",
> __func__);
> ret = EINVAL;
> goto exit;
> }
> -
> - vcpu->vc_vpid = vpid;
> }
> }
>
> @@ -2832,6 +2814,11 @@ vcpu_init_vmx(struct vcpu *vcpu)
> uint32_t cr0, cr4;
> int ret = 0;
>
> + /* Allocate a VPID early because there's no cleanup to do on failure. */
> + ret = vmm_alloc_vpid(&vcpu->vc_vpid);
> + if (ret)
> + return (ret);
> +
> /* Allocate VMCS VA */
> vcpu->vc_control_va = (vaddr_t)km_alloc(PAGE_SIZE, &kv_page, &kp_zero,
> &kd_waitok);
> @@ -3175,7 +3162,6 @@ vcpu_init_svm(struct vcpu *vcpu, struct vm_create_para
>
> /* Guest VCPU ASID */
> if (vmm_alloc_vpid(&asid)) {
> - DPRINTF("%s: could not allocate asid\n", __func__);
> ret = EINVAL;
> goto exit;
> }
>
Move VMX vpid allocation to fix vpid leak in vmm.