On 05/04/21 14:33, Laszlo Ersek wrote:
> On 04/30/21 13:51, Brijesh Singh wrote:
>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
>>
>> 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 <j...@linux.ibm.com>
>> Cc: Min Xu <min.m...@intel.com>
>> Cc: Jiewen Yao <jiewen....@intel.com>
>> Cc: Tom Lendacky <thomas.lenda...@amd.com>
>> Cc: Jordan Justen <jordan.l.jus...@intel.com>
>> Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org>
>> Cc: Laszlo Ersek <ler...@redhat.com>
>> Cc: Erdem Aktas <erdemak...@google.com>
>> Signed-off-by: Brijesh Singh <brijesh.si...@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.
Thanks
Laszlo
>
> (9) If my understanding of the spec is correct, "EndEntry" has
> *inclusive* meaning. That's unusual. Any particular reason for not
> making "EndEntry" exclusive (in the spec)?
>
>> +
>> +typedef struct {
>> + SNP_PAGE_STATE_HEADER Header;
>> + SNP_PAGE_STATE_ENTRY Entry[SNP_PAGE_STATE_MAX_ENTRY];
>> +} SNP_PAGE_STATE_CHANGE_INFO;
>> +
>> #endif
>>
>
> Yes, this looks OK. Size is 2+2+4+253*8 = 2032 bytes, which matches the
> size of GHCB.SharedBuffer.
>
> (10) However, *if* you decide to declare SNP_PAGE_STATE_ENTRY and
> SNP_PAGE_STATE_HEADER explicitly as packed, then you should do the same
> for SNP_PAGE_STATE_CHANGE_INFO.
>
> (11) Like I mentioned earlier, it's probably helpful if you start the
> subject line with
>
> MdePkg/Register/Amd: ...
>
> on all of these MdePkg patches. If that becomes too tight, for some of
> the MdePkg patches, then I suggest "MdePkg/Amd: ..." (i.e., drop
> "Register").
>
> Thanks
> Laszlo
>
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