[edk2-devel] [PATCH RFC v2 04/28] MdePkg: Define the Page State Change VMGEXIT structures
Laszlo Ersek
lersek at redhat.com
Tue May 4 18:07:24 UTC 2021
On 05/04/21 16:48, Tom Lendacky wrote:
>
>
> On 5/4/21 8:59 AM, Laszlo Ersek wrote:
>> On 05/04/21 14:33, Laszlo Ersek wrote:
>>> On 04/30/21 13:51, Brijesh Singh wrote:
>>>> BZ: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D3275&data=04%7C01%7Cthomas.lendacky%40amd.com%7Cf400bca14b6f4f138a1908d90f05090f%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637557336582189771%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=bjXNVWGpurRGUZkjemvDQR%2FYnEQRG9ENN22jUjtkNP0%3D&reserved=0
>>>>
>>>> The Page State Change NAE exit will be used by the SEV-SNP guest to
>>>> request a page state change using the GHCB protocol. See the GHCB
>>>> spec section 4.1.6 and 2.3.1 for more detail on the structure
>>>> definitions.
>>>>
>>>> Cc: James Bottomley <jejb at linux.ibm.com>
>>>> Cc: Min Xu <min.m.xu at intel.com>
>>>> Cc: Jiewen Yao <jiewen.yao at intel.com>
>>>> Cc: Tom Lendacky <thomas.lendacky at amd.com>
>>>> Cc: Jordan Justen <jordan.l.justen at intel.com>
>>>> Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
>>>> Cc: Laszlo Ersek <lersek at redhat.com>
>>>> Cc: Erdem Aktas <erdemaktas at google.com>
>>>> Signed-off-by: Brijesh Singh <brijesh.singh at amd.com>
>>>> ---
>>>> MdePkg/Include/Register/Amd/Fam17Msr.h | 15 ++++++++++
>>>> MdePkg/Include/Register/Amd/Ghcb.h | 29 ++++++++++++++++++++
>>>> 2 files changed, 44 insertions(+)
>>>>
>>>> diff --git a/MdePkg/Include/Register/Amd/Fam17Msr.h b/MdePkg/Include/Register/Amd/Fam17Msr.h
>>>> index e19bd04b6c..432cee2feb 100644
>>>> --- a/MdePkg/Include/Register/Amd/Fam17Msr.h
>>>> +++ b/MdePkg/Include/Register/Amd/Fam17Msr.h
>>>> @@ -58,6 +58,19 @@ typedef union {
>>>> UINT64 GuestFrameNumber:52;
>>>> } GhcbGpaRegister;
>>>>
>>>> + struct {
>>>> + UINT64 Function:12;
>>>> + UINT64 GuestFrameNumber:40;
>>>> + UINT64 Operation:4;
>>>> + UINT64 Reserved:8;
>>>> + } SnpPageStateChangeRequest;
>>>> +
>>>> + struct {
>>>> + UINT32 Function:12;
>>>> + UINT32 Reserved:20;
>>>> + UINT32 ErrorCode;
>>>> + } SnpPageStateChangeResponse;
>>>> +
>>>> VOID *Ghcb;
>>>>
>>> This matches section 2.3.1 in rev 2.00.
>>>
>>>> UINT64 GhcbPhysicalAddress;
>>>> @@ -69,6 +82,8 @@ typedef union {
>>>> #define GHCB_INFO_CPUID_RESPONSE 5
>>>> #define GHCB_INFO_GHCB_GPA_REGISTER_REQUEST 18
>>>> #define GHCB_INFO_GHCB_GPA_REGISTER_RESPONSE 19
>>>> +#define GHCB_INFO_SNP_PAGE_STATE_CHANGE_REQUEST 20
>>>> +#define GHCB_INFO_SNP_PAGE_STATE_CHANGE_RESPONSE 21
>>>> #define GHCB_HYPERVISOR_FEATURES_REQUEST 128
>>>> #define GHCB_HYPERVISOR_FEATURES_RESPONSE 129
>>>> #define GHCB_INFO_TERMINATE_REQUEST 256
>>>
>>> Matches section 2.3.1.
>>>
>>>> diff --git a/MdePkg/Include/Register/Amd/Ghcb.h b/MdePkg/Include/Register/Amd/Ghcb.h
>>>> index 2d64a4c28f..1e7c0daed3 100644
>>>> --- a/MdePkg/Include/Register/Amd/Ghcb.h
>>>> +++ b/MdePkg/Include/Register/Amd/Ghcb.h
>>>> @@ -54,6 +54,7 @@
>>>> #define SVM_EXIT_NMI_COMPLETE 0x80000003ULL
>>>> #define SVM_EXIT_AP_RESET_HOLD 0x80000004ULL
>>>> #define SVM_EXIT_AP_JUMP_TABLE 0x80000005ULL
>>>> +#define SVM_EXIT_SNP_PAGE_STATE_CHANGE 0x80000010ULL
>>>> #define SVM_EXIT_HYPERVISOR_FEATURES 0x8000FFFDULL
>>>> #define SVM_EXIT_UNSUPPORTED 0x8000FFFFULL
>>>>
>>>
>>> Matches "Table 5. List of Supported Non-Automatic Events".
>>>
>>>> @@ -160,4 +161,32 @@ typedef union {
>>>> #define GHCB_HV_FEATURES_SNP_AP_CREATE (GHCB_HV_FEATURES_SNP | BIT1)
>>>> #define GHCB_HV_FEATURES_SNP_RESTRICTED_INJECTION (GHCB_HV_FEATURES_SNP_AP_CREATE | BIT2)
>>>> #define GHCB_HV_FEATURES_SNP_RESTRICTED_INJECTION_TIMER (GHCB_HV_FEATURES_SNP_RESTRICTED_INJECTION | BIT3)
>>>> +
>>>> +// SNP Page State Change
>>>
>>> (1) Comment style.
>>>
>>>> +#define SNP_PAGE_STATE_MAX_NPAGES 4095
>>>> +#define SNP_PAGE_STATE_MAX_ENTRY 253
>>>> +#define SNP_PAGE_STATE_PRIVATE 1
>>>> +#define SNP_PAGE_STATE_SHARED 2
>>>> +#define SNP_PAGE_STATE_PSMASH 3
>>>> +#define SNP_PAGE_STATE_UNSMASH 4
>>>
>>> (2) The PSMASH and UNSMASH operations are not documented in the rev 2.00
>>> spec, in the GHCB MSR protocol. That's probably because PSMASH and
>>> UNSMASH can only be defined in terms of 2MB pages, and
>>> GHCB_INFO_SNP_PAGE_STATE_CHANGE_REQUEST is suitable only for individual,
>>> 4KB pages. I think it would be useful to point out somehow here that
>>> PSMASH and UNSMASH are restricted to the GHCB shared area protocol
>>> (perhaps extend the leading comment on this block of macros).
>>>
>>> (3) I don't understand what "MAX_NPAGES" stands for (4095). The rest of
>>> the series never uses the macro, and I can't associate it with anything
>>> from the spec. If the macro is supposed to relate to the 4KB / 2MB page
>>> smashing / splitting, then its replacement text should be 512. Unless
>>> the macro corresponds to a definition in the spec, I think we should
>>> drop it.
>>>
>>>> +
>>>> +typedef PACKED struct {
>>>> + UINT64 CurrentPage:12;
>>>> + UINT64 GuestFrameNumber:40;
>>>> + UINT64 Op:4;
>>>> + UINT64 PageSize:1;
>>>> + UINT64 Rsvd: 7;
>>>> +} SNP_PAGE_STATE_ENTRY;
>>>> +
>>>> +typedef PACKED struct {
>>>> + UINT16 CurrentEntry;
>>>> + UINT16 EndEntry;
>>>> + UINT32 Rsvd;
>>>> +} SNP_PAGE_STATE_HEADER;
>>>
>>> (4) We tend to write
>>>
>>> #pragma pack (1)
>>> ...
>>> #pragma pack ()
>>>
>>> rather than PACKED -- but anyway, is packing really necessary? "Natural
>>> alignment" is required in edk2. I'm OK with packing, but I think the
>>> pragma is the preferred form.
>>>
>>> (5) Please spell out both "Rsvd" fields above as "Reserved".
>>>
>>> (6) Stray space character in "Rsvd: 7".
>>>
>>> (7) The field name "Op" is inconsistent with the other field name
>>> "Operation".
>>>
>>> (8) I think there is a bug (typo) in the rev 2.00 spec, in 4.1.6 "SNP
>>> Page State Change": it says
>>>
>>> ... calculated from the supplied guest physical frame number (GFN) for
>>> the requested page size (GPA = GFN << 12).
>>>
>>> But, if you can choose 2MB page size in the request, then the (GPA = GFN
>>> << 12) formula is not g
>>
>> Sorry, unfinished sentence: I meant that the formula was not generally
>> correct.
>
> Actually, for any page size, the GPA for any GFN is GFN << 12.
>
> For the SNP Page State Change NAE event, it is up to the hypervisor to
> ensure that the GFN/GPA supplied is aligned appropriately for the
> requested page size (see 4.1.6 of the GHCB spec where the page operations
> are defined). A GFN is naturally 4K aligned, so only a 2MB page size needs
> GFN/GPA alignment validation.
Thanks. I guess I was confused by the term "for the requested page size".
> For the SNP Page State Change MSR protocol, only a 4K page size is supported.
Yes, that's clear.
Thanks!
Laszlo
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