From: Tom Lendacky <thomas.lendacky@amd.com>
To: Dave Hansen <dave.hansen@intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
"H. Peter Anvin" <hpa@zytor.com>,
Michael Roth <michael.roth@amd.com>,
Joerg Roedel <jroedel@suse.de>, Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v2 1/2] x86/sev: Put PSC struct on the stack in prep for unaccepted memory support
Date: Mon, 8 Aug 2022 17:18:54 -0500 [thread overview]
Message-ID: <6b615140-4075-4fab-de23-e0c7cd3c64d8@amd.com> (raw)
In-Reply-To: <50599c3c-eacb-7774-746c-021adf3f56e3@intel.com>
On 8/8/22 16:43, Dave Hansen wrote:
> On 8/8/22 10:16, Tom Lendacky wrote:
> ...
>> diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
>> index b8357d6ecd47..6f7268a817fc 100644
>> --- a/arch/x86/include/asm/sev-common.h
>> +++ b/arch/x86/include/asm/sev-common.h
>> @@ -107,7 +107,7 @@ enum psc_op {
>> #define GHCB_HV_FT_SNP_AP_CREATION BIT_ULL(1)
>>
>> /* SNP Page State Change NAE event */
>> -#define VMGEXIT_PSC_MAX_ENTRY 253
>> +#define VMGEXIT_PSC_MAX_ENTRY 64
>
> In general, the stack-based allocation looks fine. It might be worth a
> comment in there to make it clear that this can consume stack space.
I'll add that.
>
>> struct psc_hdr {
>> u16 cur_entry;
>> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
>> index c05f0124c410..275aa890611f 100644
>> --- a/arch/x86/kernel/sev.c
>> +++ b/arch/x86/kernel/sev.c
>> @@ -66,6 +66,9 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
>> */
>> static struct ghcb *boot_ghcb __section(".data");
>>
>> +/* Flag to indicate when the first per-CPU GHCB is registered */
>> +static bool ghcb_percpu_ready __section(".data");
>
> So, there's a code path that can't be entered until this is set? Seems
> like the least we can do it annotate that path with a
> WARN_ON_ONCE(!ghcb_percpu_ready).
Sure, that can be added. Right now the only function that calls
vmgexit_psc() is covered (set_pages_state()/__set_pages_state()) and is
doing the right thing. But I guess if anything is added in the future,
that will provide details on what happened.
>
> Also, how does having _one_ global variable work for indicating the
> state of multiple per-cpu structures? The code doesn't seem to delay
> setting this variable until after _all_ of the per-cpu state is ready.
All of the per-CPU GHCBs are allocated during the BSP boot, before any AP
is started. The APs only ever run the kernel_exc_vmm_communication() #VC
handler and only ever use the per-CPU version of the GHCB, never the early
boot version. This is based on the initial_vc_handler being switched to
the runtime #VC handler, kernel_exc_vmm_communication.
The trigger for the switch over for the BSP from the early boot GHCB to
the per-CPU GHCB is during setup_ghcb() after the initial_vc_handler has
been switched to kernel_exc_vmm_communication, which is just after the
per-CPU allocations. By putting the setting of the ghcb_percpu_ready in
setup_ghcb(), it indicates that the BSP per-CPU GHCB has been registered
and can be used.
>
>> /* Bitmap of SEV features supported by the hypervisor */
>> static u64 sev_hv_features __ro_after_init;
>>
>> @@ -660,7 +663,7 @@ static void pvalidate_pages(unsigned long vaddr, unsigned int npages, bool valid
>> }
>> }
>>
>> -static void __init early_set_pages_state(unsigned long paddr, unsigned int npages, enum psc_op op)
>> +static void early_set_pages_state(unsigned long paddr, unsigned int npages, enum psc_op op)
>> {
>> unsigned long paddr_end;
>> u64 val;
>> @@ -868,11 +871,16 @@ static void __set_pages_state(struct snp_psc_desc *data, unsigned long vaddr,
>> static void set_pages_state(unsigned long vaddr, unsigned int npages, int op)
>> {
>> unsigned long vaddr_end, next_vaddr;
>> - struct snp_psc_desc *desc;
>> + struct snp_psc_desc desc;
>> +
>> + /*
>> + * Use the MSR protocol when the per-CPU GHCBs are not yet registered,
>> + * since vmgexit_psc() uses the per-CPU GHCB.
>> + */
>> + if (!ghcb_percpu_ready)
>> + return early_set_pages_state(__pa(vaddr), npages, op);
>>
>> - desc = kmalloc(sizeof(*desc), GFP_KERNEL_ACCOUNT);
>> - if (!desc)
>> - panic("SNP: failed to allocate memory for PSC descriptor\n");
>> + memset(&desc, 0, sizeof(desc));
>
> Why is this using memset()? The compiler should be smart enough to
> delay initializing 'desc' until after the return with this kind of
> construct:
>
> struct snp_psc_desc desc = {};
> if (foo)
> return;
> // use 'desc' here
>
> The compiler *knows* there is no access to 'desc' before the if().
Yup, I can change that.
Thanks,
Tom
>
>
>> vaddr = vaddr & PAGE_MASK;
>> vaddr_end = vaddr + (npages << PAGE_SHIFT);
>> @@ -882,12 +890,10 @@ static void set_pages_state(unsigned long vaddr, unsigned int npages, int op)
>> next_vaddr = min_t(unsigned long, vaddr_end,
>> (VMGEXIT_PSC_MAX_ENTRY * PAGE_SIZE) + vaddr);
>>
>> - __set_pages_state(desc, vaddr, next_vaddr, op);
>> + __set_pages_state(&desc, vaddr, next_vaddr, op);
>>
>> vaddr = next_vaddr;
>> }
>> -
>> - kfree(desc);
>> }
>>
>> void snp_set_memory_shared(unsigned long vaddr, unsigned int npages)
>> @@ -1254,6 +1260,8 @@ void setup_ghcb(void)
>> if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
>> snp_register_per_cpu_ghcb();
>>
>> + ghcb_percpu_ready = true;
>> +
>> return;
>> }
>>
>
next prev parent reply other threads:[~2022-08-08 22:19 UTC|newest]
Thread overview: 207+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-14 12:02 [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 01/14] x86/boot: Centralize __pa()/__va() definitions Kirill A. Shutemov
2022-06-23 17:37 ` Dave Hansen
2022-06-14 12:02 ` [PATCHv7 02/14] mm: Add support for unaccepted memory Kirill A. Shutemov
2022-06-14 12:57 ` Gupta, Pankaj
2022-06-17 19:28 ` Tom Lendacky
2022-06-17 20:53 ` Tom Lendacky
2022-07-21 15:14 ` Borislav Petkov
2022-07-21 15:49 ` Dave Hansen
2022-07-22 19:18 ` Borislav Petkov
2022-07-22 19:30 ` Dave Hansen
2022-07-25 12:23 ` Borislav Petkov
2022-07-25 12:38 ` David Hildenbrand
2022-07-25 12:53 ` Borislav Petkov
2022-07-26 14:30 ` David Hildenbrand
2022-07-25 13:00 ` Mike Rapoport
2022-07-25 13:05 ` Borislav Petkov
2022-08-05 11:49 ` Vlastimil Babka
2022-08-05 12:09 ` David Hildenbrand
2022-08-05 13:38 ` Vlastimil Babka
2022-08-05 14:22 ` David Hildenbrand
2022-08-05 14:53 ` Dave Hansen
2022-08-05 14:41 ` Dave Hansen
2022-08-05 18:17 ` Vlastimil Babka
2022-08-08 15:55 ` Dave Hansen
2022-08-10 14:19 ` Mel Gorman
2022-08-15 21:08 ` Dionna Amalie Glaze
2022-08-15 22:02 ` Tom Lendacky
2022-08-29 16:02 ` Dionna Amalie Glaze
2022-08-29 16:19 ` Dave Hansen
2022-09-06 17:50 ` Dionna Amalie Glaze
2022-09-08 12:11 ` Mike Rapoport
2022-09-08 16:23 ` Dionna Amalie Glaze
2022-09-08 19:28 ` Mike Rapoport
2022-09-22 14:31 ` Tom Lendacky
2022-09-24 1:03 ` Kirill A. Shutemov
2022-09-24 9:36 ` Mike Rapoport
2022-09-26 12:10 ` Kirill A. Shutemov
2022-09-26 13:38 ` Tom Lendacky
2022-09-26 15:42 ` Kirill A. Shutemov
2022-09-26 15:42 ` Tom Lendacky
2022-06-14 12:02 ` [PATCHv7 03/14] mm: Report unaccepted memory in meminfo Kirill A. Shutemov
2022-07-26 14:33 ` David Hildenbrand
2022-06-14 12:02 ` [PATCHv7 04/14] efi/x86: Get full memory map in allocate_e820() Kirill A. Shutemov
2022-07-25 13:02 ` Borislav Petkov
2022-06-14 12:02 ` [PATCHv7 05/14] x86/boot: Add infrastructure required for unaccepted memory support Kirill A. Shutemov
2022-06-15 10:19 ` Peter Zijlstra
2022-06-15 15:05 ` Kirill A. Shutemov
2022-07-17 17:16 ` Borislav Petkov
2022-07-25 21:33 ` Borislav Petkov
2022-06-14 12:02 ` [PATCHv7 06/14] efi/x86: Implement support for unaccepted memory Kirill A. Shutemov
2022-06-22 19:58 ` Dave Hansen
2022-07-26 8:35 ` Borislav Petkov
2022-06-14 12:02 ` [PATCHv7 07/14] x86/boot/compressed: Handle " Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 08/14] x86/mm: Reserve unaccepted memory bitmap Kirill A. Shutemov
2022-07-26 9:07 ` Borislav Petkov
2022-11-30 1:28 ` Kirill A. Shutemov
2022-12-01 9:37 ` Mike Rapoport
2022-12-01 13:47 ` Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 09/14] x86/mm: Provide helpers for unaccepted memory Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 10/14] x86/mm: Avoid load_unaligned_zeropad() stepping into " Kirill A. Shutemov
2022-06-23 17:19 ` Dave Hansen
2022-07-26 10:21 ` Borislav Petkov
2022-08-02 23:46 ` Dave Hansen
2022-08-03 14:02 ` Dave Hansen
2022-08-11 11:26 ` Borislav Petkov
2022-08-13 16:11 ` Andy Lutomirski
2022-08-13 21:13 ` Kirill A. Shutemov
2022-08-13 16:04 ` Andy Lutomirski
2022-08-13 20:58 ` Kirill A. Shutemov
2022-07-26 17:25 ` Borislav Petkov
2022-07-26 17:46 ` Dave Hansen
2022-07-26 20:17 ` Andy Lutomirski
2022-08-09 11:38 ` Kirill A. Shutemov
2022-08-13 16:03 ` Andy Lutomirski
2022-08-13 21:02 ` Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 11/14] x86: Disable kexec if system has " Kirill A. Shutemov
2022-06-23 17:23 ` Dave Hansen
2022-06-23 17:23 ` Dave Hansen
2022-06-23 21:48 ` Eric W. Biederman
2022-06-23 21:48 ` Eric W. Biederman
2022-06-24 2:00 ` Kirill A. Shutemov
2022-06-24 2:00 ` Kirill A. Shutemov
2022-06-28 23:51 ` Kirill A. Shutemov
2022-06-28 23:51 ` Kirill A. Shutemov
2022-06-29 0:10 ` Dave Hansen
2022-06-29 0:10 ` Dave Hansen
2022-06-29 0:59 ` Kirill A. Shutemov
2022-06-29 0:59 ` Kirill A. Shutemov
2022-07-04 7:18 ` Dave Young
2022-07-04 7:18 ` Dave Young
2022-06-14 12:02 ` [PATCHv7 12/14] x86/tdx: Make _tdx_hypercall() and __tdx_module_call() available in boot stub Kirill A. Shutemov
2022-06-23 17:25 ` Dave Hansen
2022-06-14 12:02 ` [PATCHv7 13/14] x86/tdx: Refactor try_accept_one() Kirill A. Shutemov
2022-06-23 17:31 ` Dave Hansen
2022-07-26 10:58 ` Borislav Petkov
2022-06-14 12:02 ` [PATCHv7 14/14] x86/tdx: Add unaccepted memory support Kirill A. Shutemov
2022-06-24 16:22 ` Dave Hansen
2022-06-27 10:42 ` Kirill A. Shutemov
2022-07-26 14:51 ` Borislav Petkov
2022-08-09 11:45 ` Kirill A. Shutemov
2022-08-10 10:27 ` Borislav Petkov
2022-06-24 16:37 ` [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory Peter Gonda
2022-06-24 16:57 ` Dave Hansen
2022-06-24 17:06 ` Marc Orr
2022-06-24 17:09 ` Dave Hansen
2022-06-24 17:15 ` Peter Gonda
2022-06-24 17:19 ` Marc Orr
2022-06-24 17:21 ` Peter Gonda
2022-06-24 17:47 ` Dave Hansen
2022-06-24 18:10 ` Peter Gonda
2022-06-24 18:13 ` Dave Hansen
2022-06-24 17:40 ` Michael Roth
2022-06-24 17:58 ` Michael Roth
2022-06-24 18:05 ` Peter Gonda
2022-06-27 11:30 ` Kirill A. Shutemov
2022-06-27 11:54 ` Ard Biesheuvel
2022-06-27 12:22 ` Kirill A. Shutemov
2022-06-27 16:17 ` Peter Gonda
2022-06-27 16:33 ` Ard Biesheuvel
2022-06-27 22:38 ` Kirill A. Shutemov
2022-06-28 17:17 ` Ard Biesheuvel
2022-07-18 17:21 ` Kirill A. Shutemov
2022-07-18 23:32 ` Dionna Amalie Glaze
2022-07-19 0:31 ` Dionna Amalie Glaze
2022-07-19 18:29 ` Dionna Amalie Glaze
2022-07-19 19:13 ` Borislav Petkov
2022-07-19 20:45 ` Ard Biesheuvel
2022-07-19 21:23 ` Borislav Petkov
2022-07-19 21:35 ` Dave Hansen
2022-07-19 21:50 ` Borislav Petkov
2022-07-19 22:01 ` Kirill A. Shutemov
2022-07-19 22:02 ` Dave Hansen
2022-07-19 22:08 ` Tom Lendacky
2022-07-20 0:26 ` Marc Orr
2022-07-20 5:44 ` Borislav Petkov
2022-07-20 17:03 ` Marc Orr
2022-07-22 15:07 ` Borislav Petkov
2022-07-21 17:12 ` Dave Hansen
2022-07-23 11:14 ` Ard Biesheuvel
2022-07-28 22:01 ` Dionna Amalie Glaze
2022-08-09 11:14 ` Kirill A. Shutemov
2022-08-09 11:36 ` Ard Biesheuvel
2022-08-09 11:54 ` Kirill A. Shutemov
2022-08-09 21:09 ` Dionna Amalie Glaze
2022-07-19 2:48 ` Yao, Jiewen
2022-07-29 14:01 ` [PATCH v1 0/2] Provide SEV-SNP " Tom Lendacky
2022-07-29 14:01 ` [PATCH v1 1/2] x86/sev: Use per-CPU PSC structure in prep for unaccepted memory support Tom Lendacky
2022-07-29 14:18 ` Dave Hansen
2022-07-29 14:25 ` Tom Lendacky
2022-07-29 19:08 ` Dave Hansen
2022-07-29 19:22 ` Tom Lendacky
2022-07-29 19:28 ` Dave Hansen
2022-07-29 20:12 ` Tom Lendacky
2022-08-03 18:11 ` [PATCH v1.1 0/2] Provide SEV-SNP support for unaccepted memory Tom Lendacky
2022-08-03 18:11 ` [PATCH v1.1 1/2] x86/sev: Use per-CPU PSC structure in prep for unaccepted memory support Tom Lendacky
2022-08-03 18:17 ` Dave Hansen
2022-08-03 18:21 ` Tom Lendacky
2022-08-03 18:24 ` Dave Hansen
2022-08-03 21:03 ` Tom Lendacky
2022-08-03 21:18 ` Dave Hansen
2022-08-03 21:34 ` Tom Lendacky
2022-08-03 21:48 ` Dave Hansen
2022-08-03 22:17 ` Tom Lendacky
2022-08-03 18:18 ` Tom Lendacky
2022-08-03 18:11 ` [PATCH v1.1 2/2] x86/sev: Add SNP-specific " Tom Lendacky
2022-07-29 14:01 ` [PATCH v1 " Tom Lendacky
2022-08-23 0:24 ` Dionna Amalie Glaze
2022-08-23 14:28 ` Tom Lendacky
2022-08-23 23:28 ` Dionna Amalie Glaze
2022-08-08 17:16 ` [PATCH v2 0/2] Provide SEV-SNP support for unaccepted memory Tom Lendacky
2022-08-08 17:16 ` [PATCH v2 1/2] x86/sev: Put PSC struct on the stack in prep for unaccepted memory support Tom Lendacky
2022-08-08 21:43 ` Dave Hansen
2022-08-08 22:18 ` Tom Lendacky [this message]
2022-08-08 22:33 ` Dave Hansen
2022-08-08 22:35 ` Tom Lendacky
2022-08-12 13:03 ` Borislav Petkov
2022-08-12 14:11 ` Tom Lendacky
2022-08-12 14:33 ` Borislav Petkov
2022-08-12 14:51 ` Tom Lendacky
2022-08-13 19:40 ` Borislav Petkov
2022-08-14 13:36 ` Tom Lendacky
2022-08-08 17:16 ` [PATCH v2 2/2] x86/sev: Add SNP-specific " Tom Lendacky
2022-08-15 15:57 ` [PATCH v3 0/2] Provide SEV-SNP support for unaccepted memory Tom Lendacky
2022-08-15 15:57 ` [PATCH v3 1/2] x86/sev: Put PSC struct on the stack in prep for unaccepted memory support Tom Lendacky
2022-08-17 16:08 ` Borislav Petkov
2022-08-17 21:17 ` Tom Lendacky
2022-08-15 15:57 ` [PATCH v3 2/2] x86/sev: Add SNP-specific " Tom Lendacky
2022-08-18 13:39 ` Borislav Petkov
2022-08-25 14:23 ` [PATCH v4 0/4] Provide SEV-SNP support for unaccepted memory Tom Lendacky
2022-08-25 14:23 ` [PATCH v4 1/4] x86/sev: Put PSC struct on the stack in prep for unaccepted memory support Tom Lendacky
2022-09-20 16:15 ` Borislav Petkov
2022-08-25 14:23 ` [PATCH v4 2/4] x86/sev: Allow for use of the early boot GHCB for PSC requests Tom Lendacky
2022-08-25 14:23 ` [PATCH v4 3/4] x86/sev: Use large PSC requests if applicable Tom Lendacky
2022-08-25 14:23 ` [PATCH v4 4/4] x86/sev: Add SNP-specific unaccepted memory support Tom Lendacky
2022-08-25 22:10 ` Dionna Amalie Glaze
2022-08-26 21:29 ` Tom Lendacky
2022-09-27 17:04 ` [PATCH v5 0/6] Provide SEV-SNP support for unaccepted memory Tom Lendacky
2022-09-27 17:04 ` [PATCH v5 1/6] x86/sev: Fix calculation of end address based on number of pages Tom Lendacky
2022-09-27 17:10 ` Dave Hansen
2022-09-27 20:45 ` Tom Lendacky
2022-09-27 19:04 ` Dionna Amalie Glaze
2022-09-27 17:04 ` [PATCH v5 2/6] " Tom Lendacky
2022-09-27 17:04 ` [PATCH v5 3/6] x86/sev: Put PSC struct on the stack in prep for unaccepted memory support Tom Lendacky
2022-09-27 17:04 ` [PATCH v5 4/6] x86/sev: Allow for use of the early boot GHCB for PSC requests Tom Lendacky
2022-09-27 17:04 ` [PATCH v5 5/6] x86/sev: Use large PSC requests if applicable Tom Lendacky
2022-09-27 17:04 ` [PATCH v5 6/6] x86/sev: Add SNP-specific unaccepted memory support Tom Lendacky
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