linux-kernel - Re: [PATCH v6 12/14] KVM: x86: Introduce KVM_PAGE_ENC_BITMAP

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Message-ID: <20200403214559.GB28747@ashkalra_ubuntu_server>
Date:   Fri, 3 Apr 2020 21:45:59 +0000
From:   Ashish Kalra <ashish.kalra@....com>
To:     Krish Sadhukhan <krish.sadhukhan@...cle.com>
Cc:     pbonzini@...hat.com, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, joro@...tes.org, bp@...e.de,
        thomas.lendacky@....com, x86@...nel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, rientjes@...gle.com,
        srutherford@...gle.com, luto@...nel.org, brijesh.singh@....com
Subject: Re: [PATCH v6 12/14] KVM: x86: Introduce KVM_PAGE_ENC_BITMAP_RESET
 ioctl

On Fri, Apr 03, 2020 at 02:14:23PM -0700, Krish Sadhukhan wrote:
> 
> On 3/29/20 11:23 PM, Ashish Kalra wrote:
> > From: Ashish Kalra <ashish.kalra@....com>
> > 
> > This ioctl can be used by the application to reset the page
> > encryption bitmap managed by the KVM driver. A typical usage
> > for this ioctl is on VM reboot, on reboot, we must reinitialize
> > the bitmap.
> > 
> > Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> > ---
> >   Documentation/virt/kvm/api.rst  | 13 +++++++++++++
> >   arch/x86/include/asm/kvm_host.h |  1 +
> >   arch/x86/kvm/svm.c              | 16 ++++++++++++++++
> >   arch/x86/kvm/x86.c              |  6 ++++++
> >   include/uapi/linux/kvm.h        |  1 +
> >   5 files changed, 37 insertions(+)
> > 
> > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> > index 4d1004a154f6..a11326ccc51d 100644
> > --- a/Documentation/virt/kvm/api.rst
> > +++ b/Documentation/virt/kvm/api.rst
> > @@ -4698,6 +4698,19 @@ During the guest live migration the outgoing guest exports its page encryption
> >   bitmap, the KVM_SET_PAGE_ENC_BITMAP can be used to build the page encryption
> >   bitmap for an incoming guest.
> > +4.127 KVM_PAGE_ENC_BITMAP_RESET (vm ioctl)
> > +-----------------------------------------
> > +
> > +:Capability: basic
> > +:Architectures: x86
> > +:Type: vm ioctl
> > +:Parameters: none
> > +:Returns: 0 on success, -1 on error
> > +
> > +The KVM_PAGE_ENC_BITMAP_RESET is used to reset the guest's page encryption
> > +bitmap during guest reboot and this is only done on the guest's boot vCPU.
> > +
> > +
> >   5. The kvm_run structure
> >   ========================
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index d30f770aaaea..a96ef6338cd2 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1273,6 +1273,7 @@ struct kvm_x86_ops {
> >   				struct kvm_page_enc_bitmap *bmap);
> >   	int (*set_page_enc_bitmap)(struct kvm *kvm,
> >   				struct kvm_page_enc_bitmap *bmap);
> > +	int (*reset_page_enc_bitmap)(struct kvm *kvm);
> >   };
> >   struct kvm_arch_async_pf {
> > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> > index 313343a43045..c99b0207a443 100644
> > --- a/arch/x86/kvm/svm.c
> > +++ b/arch/x86/kvm/svm.c
> > @@ -7797,6 +7797,21 @@ static int svm_set_page_enc_bitmap(struct kvm *kvm,
> >   	return ret;
> >   }
> > +static int svm_reset_page_enc_bitmap(struct kvm *kvm)
> > +{
> > +	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> > +
> > +	if (!sev_guest(kvm))
> > +		return -ENOTTY;
> > +
> > +	mutex_lock(&kvm->lock);
> > +	/* by default all pages should be marked encrypted */
> > +	if (sev->page_enc_bmap_size)
> > +		bitmap_fill(sev->page_enc_bmap, sev->page_enc_bmap_size);
> > +	mutex_unlock(&kvm->lock);
> > +	return 0;
> > +}
> > +
> >   static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
> >   {
> >   	struct kvm_sev_cmd sev_cmd;
> > @@ -8203,6 +8218,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
> >   	.page_enc_status_hc = svm_page_enc_status_hc,
> >   	.get_page_enc_bitmap = svm_get_page_enc_bitmap,
> >   	.set_page_enc_bitmap = svm_set_page_enc_bitmap,
> > +	.reset_page_enc_bitmap = svm_reset_page_enc_bitmap,
> 
> 
> We don't need to initialize the intel ops to NULL ? It's not initialized in
> the previous patch either.
> 
> >   };

This struct is declared as "static storage", so won't the non-initialized
members be 0 ?

> >   static int __init svm_init(void)
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 05e953b2ec61..2127ed937f53 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -5250,6 +5250,12 @@ long kvm_arch_vm_ioctl(struct file *filp,
> >   			r = kvm_x86_ops->set_page_enc_bitmap(kvm, &bitmap);
> >   		break;
> >   	}
> > +	case KVM_PAGE_ENC_BITMAP_RESET: {
> > +		r = -ENOTTY;
> > +		if (kvm_x86_ops->reset_page_enc_bitmap)
> > +			r = kvm_x86_ops->reset_page_enc_bitmap(kvm);
> > +		break;
> > +	}
> >   	default:
> >   		r = -ENOTTY;
> >   	}
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index b4b01d47e568..0884a581fc37 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -1490,6 +1490,7 @@ struct kvm_enc_region {
> >   #define KVM_GET_PAGE_ENC_BITMAP	_IOW(KVMIO, 0xc5, struct kvm_page_enc_bitmap)
> >   #define KVM_SET_PAGE_ENC_BITMAP	_IOW(KVMIO, 0xc6, struct kvm_page_enc_bitmap)
> > +#define KVM_PAGE_ENC_BITMAP_RESET	_IO(KVMIO, 0xc7)
> >   /* Secure Encrypted Virtualization command */
> >   enum sev_cmd_id {
> Reviewed-by: Krish Sadhukhan <krish.sadhukhan@...cle.com>