Re: [PATCH v5 7/7] kvm, mem-hotplug: Unpin and remove nested_vmx->apic_access_page.

Paolo Bonzini
2014-09-11T09:33:51Z

Il 11/09/2014 07:38, Tang Chen ha scritto:
> Just like we removed kvm_arch->apic_access_page, nested_vmx->apic_access_page
> becomes useless for the same reason. This patch removes nested_vmx->apic_access_page,
> and use gfn_to_page() to pin it in memory when we need it, and unpin it after then.
>
> Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
> ---
> arch/x86/kvm/vmx.c | 31 +++++++++----------------------
> 1 file changed, 9 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 058c373..4aa73cb 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -374,11 +374,6 @@ struct nested_vmx {
> u64 vmcs01_tsc_offset;
> /* L2 must run next, and mustn't decide to exit to L1. */
> bool nested_run_pending;
> - /*
> - * Guest pages referred to in vmcs02 with host-physical pointers, so
> - * we must keep them pinned while L2 runs.
> - */
> - struct page *apic_access_page;
> u64 msr_ia32_feature_control;
>
> struct hrtimer preemption_timer;
> @@ -6154,11 +6149,6 @@ static void free_nested(struct vcpu_vmx *vmx)
> nested_release_vmcs12(vmx);
> if (enable_shadow_vmcs)
> free_vmcs(vmx->nested.current_shadow_vmcs);
> - /* Unpin physical memory we referred to in current vmcs02 */
> - if (vmx->nested.apic_access_page) {
> - nested_release_page(vmx->nested.apic_access_page);
> - vmx->nested.apic_access_page = 0;
> - }
>
> nested_free_all_saved_vmcss(vmx);
> }
> @@ -7983,28 +7973,31 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
> exec_control |= vmcs12->secondary_vm_exec_control;
>
> if (exec_control & SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES) {
> + struct page *page;
> /*
> * Translate L1 physical address to host physical
> * address for vmcs02. Keep the page pinned, so this
> * physical address remains valid. We keep a reference
> * to it so we can release it later.
> */
> - if (vmx->nested.apic_access_page) /* shouldn't happen */
> - nested_release_page(vmx->nested.apic_access_page);
> - vmx->nested.apic_access_page =
> - nested_get_page(vcpu, vmcs12->apic_access_addr);
> + page = nested_get_page(vcpu, vmcs12->apic_access_addr);
> /*
> * If translation failed, no matter: This feature asks
> * to exit when accessing the given address, and if it
> * can never be accessed, this feature won't do
> * anything anyway.
> */
> - if (!vmx->nested.apic_access_page)
> + if (!page)
> exec_control &=
> ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
> else
> vmcs_write64(APIC_ACCESS_ADDR,
> - page_to_phys(vmx->nested.apic_access_page));
> + page_to_phys(page));
> + /*
> + * Do not pin nested vm's apic access page in memory so
> + * that memory hotplug process is able to migrate it.
> + */
> + put_page(page);
> } else if (vm_need_virtualize_apic_accesses(vmx->vcpu.kvm)) {
> struct page *page = gfn_to_page(vmx->vcpu.kvm,
> APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
> @@ -8807,12 +8800,6 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
> /* This is needed for same reason as it was needed in prepare_vmcs02 */
> vmx->host_rsp = 0;
>
> - /* Unpin physical memory we referred to in vmcs02 */
> - if (vmx->nested.apic_access_page) {
> - nested_release_page(vmx->nested.apic_access_page);
> - vmx->nested.apic_access_page = 0;
> - }
> -
> /*
> * Do not call kvm_reload_apic_access_page() because we are now
> * running, mmu_notifier will force to reload the page's hpa for L2
>

This patch is not against the latest KVM tree. The call to
nested_get_page is now in nested_get_vmcs12_pages, and you have to
handle virtual_apic_page in a similar manner.

Paolo