Re: [PATCH v4 1/2] KVM: nVMX: enhance allocate/free_vpid to handle shadow vpid

From: Jan Kiszka
Date: Wed Sep 16 2015 - 05:12:09 EST


On 2015-09-16 09:19, Wanpeng Li wrote:
> Enhance allocate/free_vid to handle shadow vpid.
>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> arch/x86/kvm/vmx.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 9ff6a3f..c5222b8 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4155,29 +4155,28 @@ static int alloc_identity_pagetable(struct kvm *kvm)
> return r;
> }
>
> -static void allocate_vpid(struct vcpu_vmx *vmx)
> +static int allocate_vpid(void)
> {
> int vpid;
>
> - vmx->vpid = 0;
> if (!enable_vpid)
> - return;
> + return 0;
> spin_lock(&vmx_vpid_lock);
> vpid = find_first_zero_bit(vmx_vpid_bitmap, VMX_NR_VPIDS);
> - if (vpid < VMX_NR_VPIDS) {
> - vmx->vpid = vpid;
> + if (vpid < VMX_NR_VPIDS)
> __set_bit(vpid, vmx_vpid_bitmap);
> - }
> + else
> + vpid = 0;
> spin_unlock(&vmx_vpid_lock);
> + return vpid;
> }
>
> -static void free_vpid(struct vcpu_vmx *vmx)
> +static void free_vpid(int vpid)
> {
> if (!enable_vpid)

|| vpid == 0

Otherwise you clear bit zero and cause the next allocate_vpid return 0 -
from the bitmap.

Jan

> return;
> spin_lock(&vmx_vpid_lock);
> - if (vmx->vpid != 0)
> - __clear_bit(vmx->vpid, vmx_vpid_bitmap);
> + __clear_bit(vpid, vmx_vpid_bitmap);
> spin_unlock(&vmx_vpid_lock);
> }
>
> @@ -8482,7 +8481,7 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
>
> if (enable_pml)
> vmx_disable_pml(vmx);
> - free_vpid(vmx);
> + free_vpid(vmx->vpid);
> leave_guest_mode(vcpu);
> vmx_load_vmcs01(vcpu);
> free_nested(vmx);
> @@ -8501,7 +8500,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> if (!vmx)
> return ERR_PTR(-ENOMEM);
>
> - allocate_vpid(vmx);
> + vmx->vpid = allocate_vpid();
>
> err = kvm_vcpu_init(&vmx->vcpu, kvm, id);
> if (err)
> @@ -8577,7 +8576,7 @@ free_msrs:
> uninit_vcpu:
> kvm_vcpu_uninit(&vmx->vcpu);
> free_vcpu:
> - free_vpid(vmx);
> + free_vpid(vmx->vpid);
> kmem_cache_free(kvm_vcpu_cache, vmx);
> return ERR_PTR(err);
> }
>

--
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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