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Message-ID: <66416f22-5ae7-7d57-b2d1-8510da00c78a@amd.com>
Date: Wed, 5 Apr 2023 11:48:36 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Tom Lendacky <thomas.lendacky@....com>,
linux-kernel@...r.kernel.org, x86@...nel.org
Cc: bp@...en8.de, dionnaglaze@...gle.com, pgonda@...gle.com,
seanjc@...gle.com, pbonzini@...hat.com, michael.roth@....com,
ketanch@...k.ac.in
Subject: Re: [PATCH v2 04/11] virt: sev-guest: Add simplified helper to assign
vmpck
On 4/4/2023 1:56 AM, Tom Lendacky wrote:
> On 3/26/23 09:46, Nikunj A Dadhania wrote:
>> Simplify get_vmpck and prepare it to be used as an API. Update the
>> snp_guest_dev structure in snp_assign_vmpck(). Added vmpck_id to the
>> snp_guest_dev structure which can be used in SNP guest request API and
>> will remove direct use of vmpck_id command line parameter.
>
> This needs to say more about why you're doing this. The first two
> sentences need more explanation as they don't really stand on their own.
> How about the this:
Add vmpck_id to snp_guest_dev struct instead of directly using vmpck_id
command line parameter. Each SNP guest has four VMPCK, which the firmware
generates and provides to the guest in a special secrets page. Each VMPCK
has a sequence number. Simplify assignment of key and sequence number
instead of using a switch case.
> The last sentence talks about removing direct use of vmpck_id, so you
> should probably do that in this patch since it seems to be the real
> reason for all this.
I did change all places using vmpck_id to snp_dev->vmpck_id. This is the
only place the command line parameter is being used.
+ if (!snp_assign_vmpck(snp_dev, vmpck_id)) {
Regards
Nikunj
>
> Thanks,
> Tom
>
>>
>> Signed-off-by: Nikunj A Dadhania <nikunj@....com>
>> ---
>> drivers/virt/coco/sev-guest/sev-guest.c | 41 ++++++++-----------------
>> 1 file changed, 12 insertions(+), 29 deletions(-)
>>
>> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
>> index ec93dee330f2..4901ebc8fa1a 100644
>> --- a/drivers/virt/coco/sev-guest/sev-guest.c
>> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
>> @@ -45,6 +45,7 @@ struct snp_guest_dev {
>> struct snp_req_data input;
>> u32 *os_area_msg_seqno;
>> u8 *vmpck;
>> + u8 vmpck_id;
>> };
>> static u32 vmpck_id;
>> @@ -80,7 +81,7 @@ static inline unsigned int get_ctx_authsize(struct snp_guest_dev *snp_dev)
>> static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
>> {
>> dev_alert(snp_dev->dev, "Disabling vmpck_id %d to prevent IV reuse.\n",
>> - vmpck_id);
>> + snp_dev->vmpck_id);
>> memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
>> snp_dev->vmpck = NULL;
>> }
>> @@ -339,7 +340,7 @@ static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
>> memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
>> /* Encrypt the userspace provided payload */
>> - rc = enc_payload(snp_dev, seqno, req, vmpck_id);
>> + rc = enc_payload(snp_dev, seqno, req, snp_dev->vmpck_id);
>> if (rc)
>> return rc;
>> @@ -364,7 +365,6 @@ static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
>> return 0;
>> }
>> -
>> static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, u8 msg_version,
>> u8 msg_type, void *req_buf, size_t req_sz, void *resp_buf,
>> u32 resp_sz, __u64 *fw_err)
>> @@ -625,32 +625,16 @@ static const struct file_operations snp_guest_fops = {
>> .unlocked_ioctl = snp_guest_ioctl,
>> };
>> -static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
>> +bool snp_assign_vmpck(struct snp_guest_dev *dev, int vmpck_id)
>> {
>> - u8 *key = NULL;
>> + if (WARN_ON(vmpck_id > 3))
>> + return false;
>> - switch (id) {
>> - case 0:
>> - *seqno = &layout->os_area.msg_seqno_0;
>> - key = layout->vmpck0;
>> - break;
>> - case 1:
>> - *seqno = &layout->os_area.msg_seqno_1;
>> - key = layout->vmpck1;
>> - break;
>> - case 2:
>> - *seqno = &layout->os_area.msg_seqno_2;
>> - key = layout->vmpck2;
>> - break;
>> - case 3:
>> - *seqno = &layout->os_area.msg_seqno_3;
>> - key = layout->vmpck3;
>> - break;
>> - default:
>> - break;
>> - }
>> + dev->vmpck_id = vmpck_id;
>> + dev->vmpck = dev->layout->vmpck0 + vmpck_id * VMPCK_KEY_LEN;
>> + dev->os_area_msg_seqno = &dev->layout->os_area.msg_seqno_0 + vmpck_id;
>> - return key;
>> + return true;
>> }
>> static int __init sev_guest_probe(struct platform_device *pdev)
>> @@ -682,8 +666,8 @@ static int __init sev_guest_probe(struct platform_device *pdev)
>> goto e_unmap;
>> ret = -EINVAL;
>> - snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
>> - if (!snp_dev->vmpck) {
>> + snp_dev->layout = layout;
>> + if (!snp_assign_vmpck(snp_dev, vmpck_id)) {
>> dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
>> goto e_unmap;
>> }
>> @@ -697,7 +681,6 @@ static int __init sev_guest_probe(struct platform_device *pdev)
>> mutex_init(&snp_dev->cmd_mutex);
>> platform_set_drvdata(pdev, snp_dev);
>> snp_dev->dev = dev;
>> - snp_dev->layout = layout;
>> /* Allocate the shared page used for the request and response message. */
>> snp_dev->request = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
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