From: "Nikunj A. Dadhania" <nikunj@amd.com>
To: Borislav Petkov <bp@alien8.de>
Cc: linux-kernel@vger.kernel.org, thomas.lendacky@amd.com,
x86@kernel.org, kvm@vger.kernel.org, mingo@redhat.com,
tglx@linutronix.de, dave.hansen@linux.intel.com,
pgonda@google.com, seanjc@google.com, pbonzini@redhat.com
Subject: Re: [PATCH v8 04/16] virt: sev-guest: Add vmpck_id to snp_guest_dev struct
Date: Wed, 17 Apr 2024 09:48:09 +0530 [thread overview]
Message-ID: <32181e52-da8e-404c-9832-cb29e9e31064@amd.com> (raw)
In-Reply-To: <20240416090658.GBZh4_sj7ursRtzijI@fat_crate.local>
On 4/16/2024 2:36 PM, Borislav Petkov wrote:
> On Tue, Apr 16, 2024 at 11:27:24AM +0530, Nikunj A. Dadhania wrote:
>>> Why does that snp_get_os_area_msg_seqno() returns a pointer when you
>>> deref it here again?
>>>
>>> A function which returns a sequence number should return that number
>>> - not a pointer to it.
>>>
>>> Which then makes that u32 *os_area_msg_seqno redundant and you can use
>>> the function directly.
>>>
>>> IOW:
>>>
>>> static inline u32 snp_get_os_area_msg_seqno(struct snp_guest_dev *snp_dev)
>>> {
>>> return snp_dev->layout->os_area.msg_seqno_0 + snp_dev->vmpck_id;
>>
>> This patch removes setting of layour page in snp_dev structure.
>
> So?
* Instead of using snp_dev->layout, we will need to access it using platform_data->layout structure.
* Below will give incorrect value of sequence number, it will get VMPCK_0's sequence number and will add vmpck_id to that. Will work by fluke for VMPCK=0, but will fail for all other keys.
return snp_dev->layout->os_area.msg_seqno_0 + snp_dev->vmpck_id;
struct secrets_os_area {
...
u32 msg_seqno_0;
u32 msg_seqno_1;
u32 msg_seqno_2;
u32 msg_seqno_3;
...
}
* I am using vmpck_id to index to correct msg_seqno_*
Changing this to
struct secrets_os_area {
...
u32 msg_seqno[VMPCK_MAX_NUM];
...
}
>
>> static inline u32 snp_get_os_area_msg_seqno(struct snp_guest_dev *snp_dev)
>> {
>> if (!platform_data)
>> return NULL;
>>
>> return *(&platform_data->layout->os_area.msg_seqno_0 + vmpck_id);
>> }
>
> What?!
I can change the secrets_os_area like below to simplify things:
struct secrets_os_area {
...
u32 msg_seqno[VMPCK_MAX_NUM];
...
}
static inline u32 snp_get_os_area_msg_seqno(struct snp_guest_dev *snp_dev)
{
if (!platform_data)
return NULL;
return platform_data->layout->os_area.msg_seqno[snp_dev->vmpck_id];
}
>
> This snp_get_os_area_msg_seqno() is a new function added by this patch.
>
>> I had a getter for getting the os_area_msg_seqno pointer, probably not
>> a good function name.
>
> Probably you need to go back to the drawing board and think about how
> this thing should look like.
>
>>> Do you see the imbalance in the APIs?
>>
>> The msg_seqno should only be incremented by 2 (always), that was the reason to avoid a setter.
>
> And what's wrong with the setter doing the incrementation so that
> callers can't even get it wrong?
Are you suggesting that setter should always increment by 2?
static inline u32 snp_set_os_area_msg_seqno(struct snp_guest_dev *snp_dev)
{
...
os_area.msg_seqno[snp_dev->vmpck_id] += 2;
...
}
>
> It sounds to me like you should redesign this sequence number handling
> in a *separate* patch.
Sure, let me rethink and will post it as separate patch.
Regards
Nikunj
next prev parent reply other threads:[~2024-04-17 4:18 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-15 11:31 [PATCH v8 00/16] Add Secure TSC support for SNP guests Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 01/16] virt: sev-guest: Use AES GCM crypto library Nikunj A Dadhania
2024-02-27 18:25 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 02/16] virt: sev-guest: Replace dev_dbg with pr_debug Nikunj A Dadhania
2024-02-27 18:28 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 03/16] virt: sev-guest: Add SNP guest request structure Nikunj A Dadhania
2024-02-27 22:20 ` Tom Lendacky
2024-02-29 9:12 ` Nikunj A. Dadhania
2024-02-28 11:50 ` Borislav Petkov
2024-02-29 9:26 ` Nikunj A. Dadhania
2024-02-15 11:31 ` [PATCH v8 04/16] virt: sev-guest: Add vmpck_id to snp_guest_dev struct Nikunj A Dadhania
2024-04-09 10:23 ` Borislav Petkov
2024-04-16 5:57 ` Nikunj A. Dadhania
2024-04-16 9:06 ` Borislav Petkov
2024-04-17 4:18 ` Nikunj A. Dadhania [this message]
2024-02-15 11:31 ` [PATCH v8 05/16] x86/sev: Cache the secrets page address Nikunj A Dadhania
2024-04-16 14:45 ` Borislav Petkov
2024-04-17 5:27 ` Nikunj A. Dadhania
2024-04-17 7:59 ` Nikunj A. Dadhania
2024-02-15 11:31 ` [PATCH v8 06/16] virt: sev-guest: Move SNP Guest command mutex Nikunj A Dadhania
2024-04-22 13:00 ` Borislav Petkov
2024-04-23 4:22 ` Nikunj A. Dadhania
2024-04-23 10:28 ` Borislav Petkov
2024-04-23 10:42 ` Nikunj A. Dadhania
2024-04-23 11:21 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 07/16] x86/sev: Move and reorganize sev guest request api Nikunj A Dadhania
2024-04-22 13:14 ` Borislav Petkov
2024-04-23 4:26 ` Nikunj A. Dadhania
2024-04-23 13:22 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 08/16] x86/mm: Add generic guest initialization hook Nikunj A Dadhania
2024-04-22 13:20 ` Borislav Petkov
2024-04-23 4:34 ` Nikunj A. Dadhania
2024-02-15 11:31 ` [PATCH v8 09/16] x86/cpufeatures: Add synthetic Secure TSC bit Nikunj A Dadhania
2024-04-22 13:25 ` Borislav Petkov
2024-04-23 4:40 ` Nikunj A. Dadhania
2024-04-23 13:29 ` Borislav Petkov
2024-02-15 11:31 ` [PATCH v8 10/16] x86/sev: Add Secure TSC support for SNP guests Nikunj A Dadhania
2024-04-22 13:50 ` Borislav Petkov
2024-04-23 4:44 ` Nikunj A. Dadhania
2024-02-15 11:31 ` [PATCH v8 11/16] x86/sev: Change TSC MSR behavior for Secure TSC enabled guests Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 12/16] x86/sev: Prevent RDTSC/RDTSCP interception " Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 13/16] x86/kvmclock: Skip kvmclock when Secure TSC is available Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 14/16] x86/sev: Mark Secure TSC as reliable Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 15/16] x86/cpu/amd: Do not print FW_BUG for Secure TSC Nikunj A Dadhania
2024-02-15 11:31 ` [PATCH v8 16/16] x86/sev: Enable Secure TSC for SNP guests Nikunj A Dadhania
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