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

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Message-ID: <65c09963-2027-22c1-e04d-4c8c3658b2c3@oracle.com>
Date:   Mon, 6 Apr 2020 11:52:59 -0700
From:   Krish Sadhukhan <krish.sadhukhan@...cle.com>
To:     Ashish Kalra <ashish.kalra@....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 4/3/20 2:45 PM, Ashish Kalra wrote:
> 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 ?


Correct. Although, I see that 'nested_enable_evmcs' is explicitly 
initialized. We should maintain the convention, perhaps.

>
>>>    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>