Re: [PATCH v5 07/13] KVM/nVMX: Use kvm_vcpu_map when mapping the virtual APIC page

[Konrad Rzeszutek Wilk]

On Wed, Jan 09, 2019 at 10:42:07AM +0100, KarimAllah Ahmed wrote:
> Use kvm_vcpu_map when mapping the virtual APIC page since using
> kvm_vcpu_gpa_to_page() and kmap() will only work for guest memory that has
> a "struct page".
> 
> One additional semantic change is that the virtual host mapping lifecycle
> has changed a bit. It now has the same lifetime of the pinning of the
> virtual APIC page on the host side.

Could you expand a bit on the 'same lifetime .. on the host side'  to be
obvious for folks what exactly the semantic is?

And how does this ring with this comment:
> 
> Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
> ---
> v4 -> v5:
> - unmap with dirty flag
> 
> v1 -> v2:
> - Do not change the lifecycle of the mapping (pbonzini)

.. Where Paolo does not want the semantics of the mapping to be changed?

Code wise feel free to smack my Reviewed-by on it, but obviously the
question on the above comment needs to be resolved.

Thank you.

> - Use pfn_to_hpa instead of gfn_to_gpa
> ---
>  arch/x86/kvm/vmx/nested.c | 32 +++++++++++---------------------
>  arch/x86/kvm/vmx/vmx.c    |  5 ++---
>  arch/x86/kvm/vmx/vmx.h    |  2 +-
>  3 files changed, 14 insertions(+), 25 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 4127ad9..dcff99d 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -229,10 +229,7 @@ static void free_nested(struct kvm_vcpu *vcpu)
>  		kvm_release_page_dirty(vmx->nested.apic_access_page);
>  		vmx->nested.apic_access_page = NULL;
>  	}
> -	if (vmx->nested.virtual_apic_page) {
> -		kvm_release_page_dirty(vmx->nested.virtual_apic_page);
> -		vmx->nested.virtual_apic_page = NULL;
> -	}
> +	kvm_vcpu_unmap(&vmx->nested.virtual_apic_map, true);
>  	if (vmx->nested.pi_desc_page) {
>  		kunmap(vmx->nested.pi_desc_page);
>  		kvm_release_page_dirty(vmx->nested.pi_desc_page);
> @@ -2817,6 +2814,7 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
>  {
>  	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
> +	struct kvm_host_map *map;
>  	struct page *page;
>  	u64 hpa;
>  
> @@ -2849,11 +2847,7 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
>  	}
>  
>  	if (nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW)) {
> -		if (vmx->nested.virtual_apic_page) { /* shouldn't happen */
> -			kvm_release_page_dirty(vmx->nested.virtual_apic_page);
> -			vmx->nested.virtual_apic_page = NULL;
> -		}
> -		page = kvm_vcpu_gpa_to_page(vcpu, vmcs12->virtual_apic_page_addr);
> +		map = &vmx->nested.virtual_apic_map;
>  
>  		/*
>  		 * If translation failed, VM entry will fail because
> @@ -2868,11 +2862,9 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
>  		 * control.  But such a configuration is useless, so
>  		 * let's keep the code simple.
>  		 */
> -		if (!is_error_page(page)) {
> -			vmx->nested.virtual_apic_page = page;
> -			hpa = page_to_phys(vmx->nested.virtual_apic_page);
> -			vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, hpa);
> -		}
> +		if (!kvm_vcpu_map(vcpu, gpa_to_gfn(vmcs12->virtual_apic_page_addr), map))
> +			vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, pfn_to_hpa(map->pfn));
> +
>  	}
>  
>  	if (nested_cpu_has_posted_intr(vmcs12)) {
> @@ -3279,11 +3271,12 @@ static void vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
>  
>  	max_irr = find_last_bit((unsigned long *)vmx->nested.pi_desc->pir, 256);
>  	if (max_irr != 256) {
> -		vapic_page = kmap(vmx->nested.virtual_apic_page);
> +		vapic_page = vmx->nested.virtual_apic_map.hva;
> +		if (!vapic_page)
> +			return;
> +
>  		__kvm_apic_update_irr(vmx->nested.pi_desc->pir,
>  			vapic_page, &max_irr);
> -		kunmap(vmx->nested.virtual_apic_page);
> -
>  		status = vmcs_read16(GUEST_INTR_STATUS);
>  		if ((u8)max_irr > ((u8)status & 0xff)) {
>  			status &= ~0xff;
> @@ -3917,10 +3910,7 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
>  		kvm_release_page_dirty(vmx->nested.apic_access_page);
>  		vmx->nested.apic_access_page = NULL;
>  	}
> -	if (vmx->nested.virtual_apic_page) {
> -		kvm_release_page_dirty(vmx->nested.virtual_apic_page);
> -		vmx->nested.virtual_apic_page = NULL;
> -	}
> +	kvm_vcpu_unmap(&vmx->nested.virtual_apic_map, true);
>  	if (vmx->nested.pi_desc_page) {
>  		kunmap(vmx->nested.pi_desc_page);
>  		kvm_release_page_dirty(vmx->nested.pi_desc_page);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 71d88df..e13308e 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -3627,14 +3627,13 @@ static bool vmx_guest_apic_has_interrupt(struct kvm_vcpu *vcpu)
>  
>  	if (WARN_ON_ONCE(!is_guest_mode(vcpu)) ||
>  		!nested_cpu_has_vid(get_vmcs12(vcpu)) ||
> -		WARN_ON_ONCE(!vmx->nested.virtual_apic_page))
> +		WARN_ON_ONCE(!vmx->nested.virtual_apic_map.gfn))
>  		return false;
>  
>  	rvi = vmx_get_rvi();
>  
> -	vapic_page = kmap(vmx->nested.virtual_apic_page);
> +	vapic_page = vmx->nested.virtual_apic_map.hva;
>  	vppr = *((u32 *)(vapic_page + APIC_PROCPRI));
> -	kunmap(vmx->nested.virtual_apic_page);
>  
>  	return ((rvi & 0xf0) > (vppr & 0xf0));
>  }
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 6fb69d8..f618f52 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -142,7 +142,7 @@ struct nested_vmx {
>  	 * pointers, so we must keep them pinned while L2 runs.
>  	 */
>  	struct page *apic_access_page;
> -	struct page *virtual_apic_page;
> +	struct kvm_host_map virtual_apic_map;
>  	struct page *pi_desc_page;
>  
>  	struct kvm_host_map msr_bitmap_map;
> -- 
> 2.7.4
>