From: Krish Sadhukhan <krish.sadhukhan@oracle.com>
To: Ashish Kalra <ashish.kalra@amd.com>
Cc: pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com,
hpa@zytor.com, joro@8bytes.org, bp@suse.de,
thomas.lendacky@amd.com, x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, rientjes@google.com,
srutherford@google.com, luto@kernel.org, brijesh.singh@amd.com
Subject: Re: [PATCH v6 09/14] KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl
Date: Mon, 6 Apr 2020 15:07:51 -0700 [thread overview]
Message-ID: <82adee80-5322-5992-0efa-94c5ce16a9af@oracle.com> (raw)
In-Reply-To: <20200403204734.GA28542@ashkalra_ubuntu_server>
On 4/3/20 1:47 PM, Ashish Kalra wrote:
> On Fri, Apr 03, 2020 at 01:18:52PM -0700, Krish Sadhukhan wrote:
>> On 3/29/20 11:22 PM, Ashish Kalra wrote:
>>> From: Brijesh Singh <Brijesh.Singh@amd.com>
>>>
>>> The ioctl can be used to retrieve page encryption bitmap for a given
>>> gfn range.
>>>
>>> Return the correct bitmap as per the number of pages being requested
>>> by the user. Ensure that we only copy bmap->num_pages bytes in the
>>> userspace buffer, if bmap->num_pages is not byte aligned we read
>>> the trailing bits from the userspace and copy those bits as is.
>>>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: Ingo Molnar <mingo@redhat.com>
>>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>>> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
>>> Cc: Joerg Roedel <joro@8bytes.org>
>>> Cc: Borislav Petkov <bp@suse.de>
>>> Cc: Tom Lendacky <thomas.lendacky@amd.com>
>>> Cc: x86@kernel.org
>>> Cc: kvm@vger.kernel.org
>>> Cc: linux-kernel@vger.kernel.org
>>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>>> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
>>> ---
>>> Documentation/virt/kvm/api.rst | 27 +++++++++++++
>>> arch/x86/include/asm/kvm_host.h | 2 +
>>> arch/x86/kvm/svm.c | 71 +++++++++++++++++++++++++++++++++
>>> arch/x86/kvm/x86.c | 12 ++++++
>>> include/uapi/linux/kvm.h | 12 ++++++
>>> 5 files changed, 124 insertions(+)
>>>
>>> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
>>> index ebd383fba939..8ad800ebb54f 100644
>>> --- a/Documentation/virt/kvm/api.rst
>>> +++ b/Documentation/virt/kvm/api.rst
>>> @@ -4648,6 +4648,33 @@ This ioctl resets VCPU registers and control structures according to
>>> the clear cpu reset definition in the POP. However, the cpu is not put
>>> into ESA mode. This reset is a superset of the initial reset.
>>> +4.125 KVM_GET_PAGE_ENC_BITMAP (vm ioctl)
>>> +---------------------------------------
>>> +
>>> +:Capability: basic
>>> +:Architectures: x86
>>> +:Type: vm ioctl
>>> +:Parameters: struct kvm_page_enc_bitmap (in/out)
>>> +:Returns: 0 on success, -1 on error
>>> +
>>> +/* for KVM_GET_PAGE_ENC_BITMAP */
>>> +struct kvm_page_enc_bitmap {
>>> + __u64 start_gfn;
>>> + __u64 num_pages;
>>> + union {
>>> + void __user *enc_bitmap; /* one bit per page */
>>> + __u64 padding2;
>>> + };
>>> +};
>>> +
>>> +The encrypted VMs have concept of private and shared pages. The private
>>> +page is encrypted with the guest-specific key, while shared page may
>>> +be encrypted with the hypervisor key. The KVM_GET_PAGE_ENC_BITMAP can
>>> +be used to get the bitmap indicating whether the guest page is private
>>> +or shared. The bitmap can be used during the guest migration, if the page
>>> +is private then userspace need to use SEV migration commands to transmit
>>> +the page.
>>> +
>>> 5. The kvm_run structure
>>> ========================
>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>>> index 90718fa3db47..27e43e3ec9d8 100644
>>> --- a/arch/x86/include/asm/kvm_host.h
>>> +++ b/arch/x86/include/asm/kvm_host.h
>>> @@ -1269,6 +1269,8 @@ struct kvm_x86_ops {
>>> int (*enable_direct_tlbflush)(struct kvm_vcpu *vcpu);
>>> int (*page_enc_status_hc)(struct kvm *kvm, unsigned long gpa,
>>> unsigned long sz, unsigned long mode);
>>> + int (*get_page_enc_bitmap)(struct kvm *kvm,
>>> + struct kvm_page_enc_bitmap *bmap);
>>
>> Looking back at the previous patch, it seems that these two are basically
>> the setter/getter action for page encryption, though one is implemented as a
>> hypercall while the other as an ioctl. If we consider the setter/getter
>> aspect, isn't it better to have some sort of symmetry in the naming of the
>> ops ? For example,
>>
>> set_page_enc_hc
>>
>> get_page_enc_ioctl
>>
>>> };
> These are named as per their usage. While the page_enc_status_hc is a
> hypercall used by a guest to mark the page encryption bitmap, the other
> ones are ioctl interfaces used by Qemu (or Qemu alternative) to get/set
> the page encryption bitmaps, so these are named accordingly.
OK.
Please rename 'set_page_enc_hc' to 'set_page_enc_hypercall' to match
'patch_hypercall'.
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
>
>>> struct kvm_arch_async_pf {
>>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>>> index 1d8beaf1bceb..bae783cd396a 100644
>>> --- a/arch/x86/kvm/svm.c
>>> +++ b/arch/x86/kvm/svm.c
>>> @@ -7686,6 +7686,76 @@ static int svm_page_enc_status_hc(struct kvm *kvm, unsigned long gpa,
>>> return ret;
>>> }
>>> +static int svm_get_page_enc_bitmap(struct kvm *kvm,
>>> + struct kvm_page_enc_bitmap *bmap)
>>> +{
>>> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
>>> + unsigned long gfn_start, gfn_end;
>>> + unsigned long sz, i, sz_bytes;
>>> + unsigned long *bitmap;
>>> + int ret, n;
>>> +
>>> + if (!sev_guest(kvm))
>>> + return -ENOTTY;
>>> +
>>> + gfn_start = bmap->start_gfn;
>>
>> What if bmap->start_gfn is junk ?
>>
>>> + gfn_end = gfn_start + bmap->num_pages;
>>> +
>>> + sz = ALIGN(bmap->num_pages, BITS_PER_LONG) / BITS_PER_BYTE;
>>> + bitmap = kmalloc(sz, GFP_KERNEL);
>>> + if (!bitmap)
>>> + return -ENOMEM;
>>> +
>>> + /* by default all pages are marked encrypted */
>>> + memset(bitmap, 0xff, sz);
>>> +
>>> + mutex_lock(&kvm->lock);
>>> + if (sev->page_enc_bmap) {
>>> + i = gfn_start;
>>> + for_each_clear_bit_from(i, sev->page_enc_bmap,
>>> + min(sev->page_enc_bmap_size, gfn_end))
>>> + clear_bit(i - gfn_start, bitmap);
>>> + }
>>> + mutex_unlock(&kvm->lock);
>>> +
>>> + ret = -EFAULT;
>>> +
>>> + n = bmap->num_pages % BITS_PER_BYTE;
>>> + sz_bytes = ALIGN(bmap->num_pages, BITS_PER_BYTE) / BITS_PER_BYTE;
>>> +
>>> + /*
>>> + * Return the correct bitmap as per the number of pages being
>>> + * requested by the user. Ensure that we only copy bmap->num_pages
>>> + * bytes in the userspace buffer, if bmap->num_pages is not byte
>>> + * aligned we read the trailing bits from the userspace and copy
>>> + * those bits as is.
>>> + */
>>> +
>>> + if (n) {
>>
>> Is it better to check for 'num_pages' at the beginning of the function
>> rather than coming this far if bmap->num_pages is zero ?
>>
> This is not checking for "num_pages", this is basically checking if
> bmap->num_pages is not byte aligned.
>
>>> + unsigned char *bitmap_kernel = (unsigned char *)bitmap;
>>
>> Just trying to understand why you need this extra variable instead of using
>> 'bitmap' directly.
>>
> Makes the code much more readable/understandable.
>
>>> + unsigned char bitmap_user;
>>> + unsigned long offset, mask;
>>> +
>>> + offset = bmap->num_pages / BITS_PER_BYTE;
>>> + if (copy_from_user(&bitmap_user, bmap->enc_bitmap + offset,
>>> + sizeof(unsigned char)))
>>> + goto out;
>>> +
>>> + mask = GENMASK(n - 1, 0);
>>> + bitmap_user &= ~mask;
>>> + bitmap_kernel[offset] &= mask;
>>> + bitmap_kernel[offset] |= bitmap_user;
>>> + }
>>> +
>>> + if (copy_to_user(bmap->enc_bitmap, bitmap, sz_bytes))
>>
>> If 'n' is zero, we are still copying stuff back to the user. Is that what is
>> expected from userland ?
>>
>> Another point. Since copy_from_user() was done in the caller, isn't it
>> better to move this to the caller to keep a symmetry ?
>>
> As per the comments above, please note if n is not zero that means
> bmap->num_pages is not byte aligned so we read the trailing bits
> from the userspace and copy those bits as is. If n is zero, then
> bmap->num_pages is correctly aligned and we copy all the bytes back.
>
> Thanks,
> Ashish
>
>>> + goto out;
>>> +
>>> + ret = 0;
>>> +out:
>>> + kfree(bitmap);
>>> + return ret;
>>> +}
>>> +
>>> static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>>> {
>>> struct kvm_sev_cmd sev_cmd;
>>> @@ -8090,6 +8160,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
>>> .apic_init_signal_blocked = svm_apic_init_signal_blocked,
>>> .page_enc_status_hc = svm_page_enc_status_hc,
>>> + .get_page_enc_bitmap = svm_get_page_enc_bitmap,
>>> };
>>> static int __init svm_init(void)
>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>>> index 68428eef2dde..3c3fea4e20b5 100644
>>> --- a/arch/x86/kvm/x86.c
>>> +++ b/arch/x86/kvm/x86.c
>>> @@ -5226,6 +5226,18 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>> case KVM_SET_PMU_EVENT_FILTER:
>>> r = kvm_vm_ioctl_set_pmu_event_filter(kvm, argp);
>>> break;
>>> + case KVM_GET_PAGE_ENC_BITMAP: {
>>> + struct kvm_page_enc_bitmap bitmap;
>>> +
>>> + r = -EFAULT;
>>> + if (copy_from_user(&bitmap, argp, sizeof(bitmap)))
>>> + goto out;
>>> +
>>> + r = -ENOTTY;
>>> + if (kvm_x86_ops->get_page_enc_bitmap)
>>> + r = kvm_x86_ops->get_page_enc_bitmap(kvm, &bitmap);
>>> + break;
>>> + }
>>> default:
>>> r = -ENOTTY;
>>> }
>>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>>> index 4e80c57a3182..db1ebf85e177 100644
>>> --- a/include/uapi/linux/kvm.h
>>> +++ b/include/uapi/linux/kvm.h
>>> @@ -500,6 +500,16 @@ struct kvm_dirty_log {
>>> };
>>> };
>>> +/* for KVM_GET_PAGE_ENC_BITMAP */
>>> +struct kvm_page_enc_bitmap {
>>> + __u64 start_gfn;
>>> + __u64 num_pages;
>>> + union {
>>> + void __user *enc_bitmap; /* one bit per page */
>>> + __u64 padding2;
>>> + };
>>> +};
>>> +
>>> /* for KVM_CLEAR_DIRTY_LOG */
>>> struct kvm_clear_dirty_log {
>>> __u32 slot;
>>> @@ -1478,6 +1488,8 @@ struct kvm_enc_region {
>>> #define KVM_S390_NORMAL_RESET _IO(KVMIO, 0xc3)
>>> #define KVM_S390_CLEAR_RESET _IO(KVMIO, 0xc4)
>>> +#define KVM_GET_PAGE_ENC_BITMAP _IOW(KVMIO, 0xc5, struct kvm_page_enc_bitmap)
>>> +
>>> /* Secure Encrypted Virtualization command */
>>> enum sev_cmd_id {
>>> /* Guest initialization commands */
next prev parent reply other threads:[~2020-04-06 22:08 UTC|newest]
Thread overview: 107+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 6:19 [PATCH v6 00/14] Add AMD SEV guest live migration support Ashish Kalra
2020-03-30 6:19 ` [PATCH v6 01/14] KVM: SVM: Add KVM_SEV SEND_START command Ashish Kalra
2020-04-02 6:27 ` Venu Busireddy
2020-04-02 12:59 ` Brijesh Singh
2020-04-02 16:37 ` Venu Busireddy
2020-04-02 18:04 ` Brijesh Singh
2020-04-02 18:57 ` Venu Busireddy
2020-04-02 19:17 ` Brijesh Singh
2020-04-02 19:43 ` Venu Busireddy
2020-04-02 20:04 ` Brijesh Singh
2020-04-02 20:19 ` Venu Busireddy
2020-04-02 17:51 ` Krish Sadhukhan
2020-04-02 18:38 ` Brijesh Singh
2020-03-30 6:20 ` [PATCH v6 02/14] KVM: SVM: Add KVM_SEND_UPDATE_DATA command Ashish Kalra
2020-04-02 17:55 ` Venu Busireddy
2020-04-02 20:13 ` Krish Sadhukhan
2020-03-30 6:20 ` [PATCH v6 03/14] KVM: SVM: Add KVM_SEV_SEND_FINISH command Ashish Kalra
2020-04-02 18:17 ` Venu Busireddy
2020-04-02 20:15 ` Krish Sadhukhan
2020-03-30 6:21 ` [PATCH v6 04/14] KVM: SVM: Add support for KVM_SEV_RECEIVE_START command Ashish Kalra
2020-04-02 21:35 ` Venu Busireddy
2020-04-02 22:09 ` Krish Sadhukhan
2020-03-30 6:21 ` [PATCH v6 05/14] KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command Ashish Kalra
2020-04-02 22:25 ` Krish Sadhukhan
2020-04-02 22:29 ` Venu Busireddy
2020-04-07 0:49 ` Steve Rutherford
2020-03-30 6:21 ` [PATCH v6 06/14] KVM: SVM: Add KVM_SEV_RECEIVE_FINISH command Ashish Kalra
2020-04-02 22:24 ` Venu Busireddy
2020-04-02 22:27 ` Krish Sadhukhan
2020-04-07 0:57 ` Steve Rutherford
2020-03-30 6:21 ` [PATCH v6 07/14] KVM: x86: Add AMD SEV specific Hypercall3 Ashish Kalra
2020-04-02 22:36 ` Venu Busireddy
2020-04-02 23:54 ` Krish Sadhukhan
2020-04-07 1:22 ` Steve Rutherford
2020-03-30 6:22 ` [PATCH v6 08/14] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall Ashish Kalra
2020-04-03 0:00 ` Venu Busireddy
2020-04-03 1:31 ` Krish Sadhukhan
2020-04-03 1:57 ` Ashish Kalra
2020-04-03 2:58 ` Ashish Kalra
2020-04-06 22:27 ` Krish Sadhukhan
2020-04-07 2:17 ` Steve Rutherford
2020-04-07 5:27 ` Ashish Kalra
2020-04-08 0:01 ` Steve Rutherford
2020-04-08 0:29 ` Brijesh Singh
2020-04-08 0:35 ` Steve Rutherford
2020-04-08 1:17 ` Ashish Kalra
2020-04-08 1:38 ` Steve Rutherford
2020-04-08 2:34 ` Brijesh Singh
2020-04-08 3:18 ` Ashish Kalra
2020-04-09 16:18 ` Ashish Kalra
2020-04-09 20:41 ` Steve Rutherford
2020-03-30 6:22 ` [PATCH v6 09/14] KVM: x86: Introduce KVM_GET_PAGE_ENC_BITMAP ioctl Ashish Kalra
2020-04-03 18:30 ` Venu Busireddy
2020-04-03 20:18 ` Krish Sadhukhan
2020-04-03 20:47 ` Ashish Kalra
2020-04-06 22:07 ` Krish Sadhukhan [this message]
2020-04-03 20:55 ` Venu Busireddy
2020-04-03 21:01 ` Ashish Kalra
2020-03-30 6:22 ` [PATCH v6 10/14] mm: x86: Invoke hypercall when page encryption status is changed Ashish Kalra
2020-04-03 21:07 ` Krish Sadhukhan
2020-04-03 21:30 ` Ashish Kalra
2020-04-03 21:36 ` Venu Busireddy
2020-03-30 6:22 ` [PATCH v6 11/14] KVM: x86: Introduce KVM_SET_PAGE_ENC_BITMAP ioctl Ashish Kalra
2020-04-03 21:10 ` Krish Sadhukhan
2020-04-03 21:46 ` Venu Busireddy
2020-04-08 0:26 ` Steve Rutherford
2020-04-08 1:48 ` Ashish Kalra
2020-04-10 0:06 ` Steve Rutherford
2020-04-10 1:23 ` Ashish Kalra
2020-04-10 18:08 ` Steve Rutherford
2020-03-30 6:23 ` [PATCH v6 12/14] KVM: x86: Introduce KVM_PAGE_ENC_BITMAP_RESET ioctl Ashish Kalra
2020-04-03 21:14 ` Krish Sadhukhan
2020-04-03 21:45 ` Ashish Kalra
2020-04-06 18:52 ` Krish Sadhukhan
2020-04-08 1:25 ` Steve Rutherford
2020-04-08 1:52 ` Ashish Kalra
2020-04-10 0:59 ` Steve Rutherford
2020-04-10 1:34 ` Ashish Kalra
2020-04-10 18:14 ` Steve Rutherford
2020-04-10 20:16 ` Steve Rutherford
2020-04-10 20:18 ` Steve Rutherford
2020-04-10 20:55 ` Kalra, Ashish
2020-04-10 21:42 ` Brijesh Singh
2020-04-10 21:46 ` Sean Christopherson
2020-04-10 21:58 ` Brijesh Singh
2020-04-10 22:02 ` Brijesh Singh
2020-04-11 0:35 ` Ashish Kalra
2020-04-03 22:01 ` Venu Busireddy
2020-03-30 6:23 ` [PATCH v6 13/14] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR Ashish Kalra
2020-03-30 15:52 ` Brijesh Singh
2020-03-30 16:42 ` Ashish Kalra
[not found] ` <20200330162730.GA21567@ashkalra_ubuntu_server>
[not found] ` <1de5e95f-4485-f2ff-aba8-aa8b15564796@amd.com>
[not found] ` <20200331171336.GA24050@ashkalra_ubuntu_server>
[not found] ` <20200401070931.GA8562@ashkalra_ubuntu_server>
2020-04-02 23:29 ` Ashish Kalra
2020-04-03 23:46 ` Krish Sadhukhan
2020-03-30 6:23 ` [PATCH v6 14/14] KVM: x86: Add kexec support for SEV Live Migration Ashish Kalra
2020-03-30 16:00 ` Brijesh Singh
2020-03-30 16:45 ` Ashish Kalra
2020-03-31 14:26 ` Brijesh Singh
2020-04-02 23:34 ` Ashish Kalra
2020-04-03 12:57 ` Dave Young
2020-04-04 0:55 ` Krish Sadhukhan
2020-04-04 21:57 ` Ashish Kalra
2020-04-06 18:37 ` Krish Sadhukhan
2020-03-30 17:24 ` [PATCH v6 00/14] Add AMD SEV guest live migration support Venu Busireddy
2020-03-30 18:28 ` Ashish Kalra
2020-03-30 19:13 ` Venu Busireddy
2020-03-30 21:52 ` Ashish Kalra
2020-03-31 14:42 ` Venu Busireddy
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