From: Brijesh Singh <brijesh.singh@amd.com>
To: Borislav Petkov <bp@alien8.de>
Cc: brijesh.singh@amd.com, x86@kernel.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
linux-coco@lists.linux.dev, linux-mm@kvack.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Ard Biesheuvel <ardb@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Dov Murik <dovmurik@linux.ibm.com>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
Michael Roth <michael.roth@amd.com>,
Vlastimil Babka <vbabka@suse.cz>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Andi Kleen <ak@linux.intel.com>,
tony.luck@intel.com, marcorr@google.com,
sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH Part1 v5 34/38] x86/sev: Add snp_msg_seqno() helper
Date: Mon, 30 Aug 2021 10:07:39 -0500 [thread overview]
Message-ID: <9e0e734d-7d2f-4703-b9ce-8362f0c740f4@amd.com> (raw)
In-Reply-To: <YSkxxkVdupkyxAJi@zn.tnic>
On 8/27/21 1:41 PM, Borislav Petkov wrote:
> On Fri, Aug 20, 2021 at 10:19:29AM -0500, Brijesh Singh wrote:
>> The SNP guest request message header contains a message count. The
>> message count is used while building the IV. The PSP firmware increments
>> the message count by 1, and expects that next message will be using the
>> incremented count. The snp_msg_seqno() helper will be used by driver to
>> get the message sequence counter used in the request message header,
>> and it will be automatically incremented after the request is successful.
>> The incremented value is saved in the secrets page so that the kexec'ed
>> kernel knows from where to begin.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>> ---
>> arch/x86/kernel/sev.c | 79 +++++++++++++++++++++++++++++++++++++++
>> include/linux/sev-guest.h | 37 ++++++++++++++++++
>> 2 files changed, 116 insertions(+)
>>
>> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
>> index 319a40fc57ce..f42cd5a8e7bb 100644
>> --- a/arch/x86/kernel/sev.c
>> +++ b/arch/x86/kernel/sev.c
>> @@ -51,6 +51,8 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
>> */
>> static struct ghcb __initdata *boot_ghcb;
>>
>
> Explain what that is in a comment above it.
>
>> +static u64 snp_secrets_phys;
>
> snp_secrets_pa;
>
> is the usual convention when a variable is supposed to contain a
> physical address.
>
Noted.
>> +
>> /* #VC handler runtime per-CPU data */
>> struct sev_es_runtime_data {
>> struct ghcb ghcb_page;
>> @@ -2030,6 +2032,80 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
>> halt();
>> }
>>
>> +static struct snp_secrets_page_layout *snp_map_secrets_page(void)
>> +{
>> + u16 __iomem *secrets;
>> +
>> + if (!snp_secrets_phys || !sev_feature_enabled(SEV_SNP))
>> + return NULL;
>> +
>> + secrets = ioremap_encrypted(snp_secrets_phys, PAGE_SIZE);
>> + if (!secrets)
>> + return NULL;
>> +
>> + return (struct snp_secrets_page_layout *)secrets;
>> +}
>
> Or simply:
>
> static struct snp_secrets_page_layout *map_secrets_page(void)
> {
> if (!snp_secrets_phys || !sev_feature_enabled(SEV_SNP))
> return NULL;
>
> return ioremap_encrypted(snp_secrets_phys, PAGE_SIZE);
> }
>
> ?
>
Yes that also works.
>> +
>> +static inline u64 snp_read_msg_seqno(void)
>
> Drop that "snp_" prefix from all those static function names. This one
> is even inline, which means its name doesn't matter at all.
>
>> +{
>> + struct snp_secrets_page_layout *layout;
>> + u64 count;
>> +
>> + layout = snp_map_secrets_page();
>> + if (!layout)
>> + return 0;
>> +
>> + /* Read the current message sequence counter from secrets pages */
>> + count = readl(&layout->os_area.msg_seqno_0);
>> +
>> + iounmap(layout);
>> +
>> + /* The sequence counter must begin with 1 */
>
> That sounds weird. Why? 0 is special?
The SNP firmware spec says that counter must begin with the 1.
>
>> + if (!count)
>> + return 1;
>> +
>> + return count + 1;
>> +}
>> +
>> +u64 snp_msg_seqno(void)
>
> Function name needs a verb. I.e.,
>
> snp_get_msg_seqno()
>
Ok.
>> +{
>> + u64 count = snp_read_msg_seqno();
>> +
>> + if (unlikely(!count))
>
> That looks like a left-over from a previous version as it can't happen.
>
> Or are you handling the case where the u64 count will wraparound to 0?
>
> But "The sequence counter must begin with 1" so that read function above
> needs more love.
>
Yes, I will cleanup a bit more.
>> + return 0;
>
>
>> +
>> + /*
>> + * The message sequence counter for the SNP guest request is a
>> + * 64-bit value but the version 2 of GHCB specification defines a
>> + * 32-bit storage for the it.
>> + */
>> + if (count >= UINT_MAX)
>> + return 0;
>
> Huh, WTF? So when the internal counter goes over u32, this function will
> return 0 only? More weird.
>
During the GHCB writing the seqno use to be 32-bit value and hence the
GHCB spec choose the 32-bit value but recently the SNP firmware changed
it from the 32 to 64. So, now we are left with the option of limiting
the sequence number to 32-bit. If we go beyond 32-bit then all we can do
is fail the call. If we pass the value of zero then FW will fail the call.
>> +
>> + return count;
>> +}
>> +EXPORT_SYMBOL_GPL(snp_msg_seqno);
>> +
>> +static void snp_gen_msg_seqno(void)
>
> That's not "gen" - that's "inc" what this function does. IOW,
>
> snp_inc_msg_seqno
>
I agree. I will update it.
>> +{
>> + struct snp_secrets_page_layout *layout;
>> + u64 count;
>> +
>> + layout = snp_map_secrets_page();
>> + if (!layout)
>> + return;
>> +
>> + /*
>> + * The counter is also incremented by the PSP, so increment it by 2
>> + * and save in secrets page.
>> + */
>> + count = readl(&layout->os_area.msg_seqno_0);
>> + count += 2;
>> +
>> + writel(count, &layout->os_area.msg_seqno_0);
>> + iounmap(layout);
>
> Why does this need to constantly map and unmap the secrets page? Why
> don't you map it once on init and unmap it on exit?
>
Yes, I can remove that with:
secrets_va = (__force void *)ioremap_encrypted(pa...)
And then use secrets_va instead of doing readl/writel.
>> +}
>> +
>> int snp_issue_guest_request(int type, struct snp_guest_request_data *input, unsigned long *fw_err)
>> {
>> struct ghcb_state state;
>> @@ -2077,6 +2153,9 @@ int snp_issue_guest_request(int type, struct snp_guest_request_data *input, unsi
>> ret = -EIO;
>> }
>>
>> + /* The command was successful, increment the sequence counter */
>> + snp_gen_msg_seqno();
>> +
>> e_put:
>> __sev_put_ghcb(&state);
>> e_restore_irq:
>> diff --git a/include/linux/sev-guest.h b/include/linux/sev-guest.h
>> index 24dd17507789..16b6af24fda7 100644
>> --- a/include/linux/sev-guest.h
>> +++ b/include/linux/sev-guest.h
>> @@ -20,6 +20,41 @@ enum vmgexit_type {
>> GUEST_REQUEST_MAX
>> };
>>
>> +/*
>> + * The secrets page contains 96-bytes of reserved field that can be used by
>> + * the guest OS. The guest OS uses the area to save the message sequence
>> + * number for each VMPCK.
>> + *
>> + * See the GHCB spec section Secret page layout for the format for this area.
>> + */
>> +struct secrets_os_area {
>> + u32 msg_seqno_0;
>> + u32 msg_seqno_1;
>> + u32 msg_seqno_2;
>> + u32 msg_seqno_3;
>> + u64 ap_jump_table_pa;
>> + u8 rsvd[40];
>> + u8 guest_usage[32];
>> +} __packed;
>
> So those are differently named there:
>
> struct secrets_page_os_area {
> uint32 vmpl0_message_seq_num;
> uint32 vmpl1_message_seq_num;
> ...
>
> and they have "vmpl" in there which makes a lot more sense for that
> they're used than msg_seqno_* does.
>
I just choose the smaller name but I have no issues matching with the
spec. Also those keys does not have anything to do with the VMPL level.
The secrets page provides 4 different keys and they are referred as
vmpck0..3 and each of them have a sequence numbers associated with it.
In GHCB v3 we probably need to rework the structure name.
>> +
>> +#define VMPCK_KEY_LEN 32
>> +
>> +/* See the SNP spec for secrets page format */
>> +struct snp_secrets_page_layout {
>
> Simply
>
> struct snp_secrets
>
> That name says all you need to know about what that struct represents.
>
>> + u32 version;
>> + u32 imien : 1,
>> + rsvd1 : 31;
>> + u32 fms;
>> + u32 rsvd2;
>> + u8 gosvw[16];
>> + u8 vmpck0[VMPCK_KEY_LEN];
>> + u8 vmpck1[VMPCK_KEY_LEN];
>> + u8 vmpck2[VMPCK_KEY_LEN];
>> + u8 vmpck3[VMPCK_KEY_LEN];
>> + struct secrets_os_area os_area;
>
> My SNP spec copy has here
>
> 0A0h–FFFh Reserved.
>
> and no os area. I guess
>
> SEV Secure Nested Paging Firmware ABI Specification 56860 Rev. 0.8 August 2020
>
> needs updating...
The latest SNP spec here:
https://www.amd.com/system/files/TechDocs/56860.pdf
We are at spec 0.9.
>
>> + u8 rsvd3[3840];
>> +} __packed;
>> +
>> /*
>> * The error code when the data_npages is too small. The error code
>> * is defined in the GHCB specification.
>> @@ -36,6 +71,7 @@ struct snp_guest_request_data {
>> #ifdef CONFIG_AMD_MEM_ENCRYPT
>> int snp_issue_guest_request(int vmgexit_type, struct snp_guest_request_data *input,
>> unsigned long *fw_err);
>> +u64 snp_msg_seqno(void);
>> #else
>>
>> static inline int snp_issue_guest_request(int type, struct snp_guest_request_data *input,
>> @@ -43,6 +79,7 @@ static inline int snp_issue_guest_request(int type, struct snp_guest_request_dat
>> {
>> return -ENODEV;
>> }
>> +static inline u64 snp_msg_seqno(void) { return 0; }
>>
>> #endif /* CONFIG_AMD_MEM_ENCRYPT */
>> #endif /* __LINUX_SEV_GUEST_H__ */
>> --
>> 2.17.1
>>
>
next prev parent reply other threads:[~2021-08-30 15:07 UTC|newest]
Thread overview: 123+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-20 15:18 [PATCH Part1 v5 00/38] Add AMD Secure Nested Paging (SEV-SNP) Guest Support Brijesh Singh
2021-08-20 15:18 ` [PATCH Part1 v5 01/38] x86/mm: Add sev_feature_enabled() helper Brijesh Singh
2021-08-20 15:18 ` [PATCH Part1 v5 02/38] x86/sev: Shorten GHCB terminate macro names Brijesh Singh
2021-08-20 15:18 ` [PATCH Part1 v5 03/38] x86/sev: Get rid of excessive use of defines Brijesh Singh
2021-08-20 15:18 ` [PATCH Part1 v5 04/38] x86/head64: Carve out the guest encryption postprocessing into a helper Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 05/38] x86/sev: Define the Linux specific guest termination reasons Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 06/38] x86/sev: Save the negotiated GHCB version Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 07/38] x86/sev: Add support for hypervisor feature VMGEXIT Brijesh Singh
2021-08-23 9:47 ` Borislav Petkov
2021-08-23 18:25 ` Brijesh Singh
2021-08-23 18:34 ` Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 08/38] x86/sev: Check SEV-SNP features support Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 09/38] x86/sev: Add a helper for the PVALIDATE instruction Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 10/38] x86/sev: Check the vmpl level Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 11/38] x86/compressed: Add helper for validating pages in the decompression stage Brijesh Singh
2021-08-23 14:16 ` Borislav Petkov
2021-08-23 18:55 ` Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 12/38] x86/compressed: Register GHCB memory when SEV-SNP is active Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 13/38] x86/sev: " Brijesh Singh
2021-08-23 17:35 ` Borislav Petkov
2021-08-23 18:56 ` Brijesh Singh
2021-08-23 19:45 ` [PATCH] x86/sev: Remove do_early_exception() forward declarations Borislav Petkov
2021-08-23 20:06 ` Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 14/38] x86/sev: Add helper for validating pages in early enc attribute changes Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 15/38] x86/kernel: Make the bss.decrypted section shared in RMP table Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 16/38] x86/kernel: Validate rom memory before accessing when SEV-SNP is active Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 17/38] x86/mm: Add support to validate memory when changing C-bit Brijesh Singh
2021-08-25 11:06 ` Borislav Petkov
2021-08-25 13:54 ` Brijesh Singh
2021-08-25 14:00 ` Borislav Petkov
2021-08-27 17:09 ` Borislav Petkov
2021-08-20 15:19 ` [PATCH Part1 v5 18/38] KVM: SVM: Define sev_features and vmpl field in the VMSA Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 19/38] KVM: SVM: Create a separate mapping for the SEV-ES save area Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 20/38] KVM: SVM: Create a separate mapping for the GHCB " Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 21/38] KVM: SVM: Update the SEV-ES save area mapping Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 22/38] x86/sev: Use SEV-SNP AP creation to start secondary CPUs Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 23/38] x86/head/64: set up a startup %gs for stack protector Brijesh Singh
2021-08-25 14:29 ` Borislav Petkov
2021-08-25 15:18 ` Michael Roth
2021-08-25 16:29 ` Borislav Petkov
2021-08-27 13:38 ` Michael Roth
2021-08-31 8:03 ` Borislav Petkov
2021-08-31 23:30 ` Michael Roth
2021-08-25 15:07 ` Joerg Roedel
2021-08-25 17:07 ` Michael Roth
2021-08-20 15:19 ` [PATCH Part1 v5 24/38] x86/sev: move MSR-based VMGEXITs for CPUID to helper Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 25/38] KVM: x86: move lookup of indexed CPUID leafs " Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 26/38] x86/compressed/acpi: move EFI config table access to common code Brijesh Singh
2021-08-25 15:18 ` Borislav Petkov
2021-08-25 17:14 ` Michael Roth
2021-08-20 15:19 ` [PATCH Part1 v5 27/38] x86/boot: Add Confidential Computing type to setup_data Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 28/38] x86/compressed/64: enable SEV-SNP-validated CPUID in #VC handler Brijesh Singh
2021-08-25 19:19 ` Borislav Petkov
2021-08-27 16:46 ` Michael Roth
2021-08-31 10:04 ` Borislav Petkov
2021-09-01 1:03 ` Michael Roth
2021-09-02 10:53 ` Borislav Petkov
2021-08-20 15:19 ` [PATCH Part1 v5 29/38] x86/boot: add a pointer to Confidential Computing blob in bootparams Brijesh Singh
2021-08-27 13:51 ` Borislav Petkov
2021-08-27 18:48 ` Michael Roth
2021-08-20 15:19 ` [PATCH Part1 v5 30/38] x86/compressed/64: store Confidential Computing blob address " Brijesh Singh
2021-08-27 14:15 ` Borislav Petkov
2021-08-27 19:09 ` Michael Roth
2021-08-31 10:26 ` Borislav Petkov
2021-08-20 15:19 ` [PATCH Part1 v5 31/38] x86/compressed/64: add identity mapping for Confidential Computing blob Brijesh Singh
2021-08-27 14:43 ` Borislav Petkov
2021-08-20 15:19 ` [PATCH Part1 v5 32/38] x86/sev: enable SEV-SNP-validated CPUID in #VC handlers Brijesh Singh
2021-08-27 15:18 ` Borislav Petkov
2021-08-27 15:47 ` Brijesh Singh
2021-08-27 16:56 ` Borislav Petkov
2021-08-27 18:39 ` Michael Roth
2021-08-27 18:32 ` Michael Roth
2021-08-30 16:03 ` Michael Roth
2021-08-31 16:22 ` Borislav Petkov
2021-09-01 1:16 ` Michael Roth
2021-09-02 11:05 ` Borislav Petkov
2021-08-20 15:19 ` [PATCH Part1 v5 33/38] x86/sev: Provide support for SNP guest request NAEs Brijesh Singh
2021-08-27 17:44 ` Borislav Petkov
2021-08-27 18:07 ` Brijesh Singh
2021-08-27 18:13 ` Borislav Petkov
2021-08-27 18:27 ` Brijesh Singh
2021-08-27 18:38 ` Borislav Petkov
2021-08-27 19:57 ` Tom Lendacky
2021-08-27 20:17 ` Borislav Petkov
2021-08-27 20:31 ` Tom Lendacky
2021-08-20 15:19 ` [PATCH Part1 v5 34/38] x86/sev: Add snp_msg_seqno() helper Brijesh Singh
2021-08-27 18:41 ` Borislav Petkov
2021-08-30 15:07 ` Brijesh Singh [this message]
2021-09-02 11:26 ` Borislav Petkov
2021-09-02 15:27 ` Brijesh Singh
2021-08-31 20:46 ` Dov Murik
2021-08-31 21:13 ` Brijesh Singh
2021-09-09 14:54 ` Peter Gonda
2021-09-09 15:26 ` Brijesh Singh
2021-09-09 15:43 ` Peter Gonda
2021-09-09 16:17 ` Brijesh Singh
2021-09-09 16:21 ` Peter Gonda
2021-09-09 19:26 ` Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 35/38] x86/sev: Register SNP guest request platform device Brijesh Singh
2021-08-31 11:37 ` Dov Murik
2021-08-31 16:03 ` Brijesh Singh
2021-09-02 16:40 ` Borislav Petkov
2021-09-02 19:58 ` Brijesh Singh
2021-09-03 8:15 ` Dov Murik
2021-09-03 12:08 ` Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 36/38] virt: Add SEV-SNP guest driver Brijesh Singh
2021-09-06 17:38 ` Borislav Petkov
2021-09-07 13:35 ` Brijesh Singh
2021-09-08 13:44 ` Borislav Petkov
2021-08-20 15:19 ` [PATCH Part1 v5 37/38] virt: sevguest: Add support to derive key Brijesh Singh
2021-08-31 18:59 ` Dov Murik
2021-08-31 21:04 ` Brijesh Singh
2021-09-01 5:33 ` Dov Murik
2021-09-08 14:00 ` Borislav Petkov
2021-09-08 21:44 ` Brijesh Singh
2021-08-20 15:19 ` [PATCH Part1 v5 38/38] virt: sevguest: Add support to get extended report Brijesh Singh
2021-08-31 20:22 ` Dov Murik
2021-08-31 21:11 ` Brijesh Singh
2021-09-01 8:32 ` Dov Murik
2021-09-08 17:53 ` Borislav Petkov
2021-09-15 11:46 ` Brijesh Singh
2021-09-15 10:02 ` Dr. David Alan Gilbert
2021-09-15 11:53 ` Brijesh Singh
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