From: "Wu, Jiaxin" <jiaxin.wu@intel.com>
To: Laszlo Ersek <lersek@redhat.com>, "Ni, Ray" <ray.ni@intel.com>,
"Gerd Hoffmann" <kraxel@redhat.com>
Cc: "devel@edk2.groups.io" <devel@edk2.groups.io>,
"Dong, Eric" <eric.dong@intel.com>,
"Zeng, Star" <star.zeng@intel.com>,
"Kumar, Rahul R" <rahul.r.kumar@intel.com>,
"Kinney, Michael D" <michael.d.kinney@intel.com>,
"Zimmer, Vincent" <vincent.zimmer@intel.com>
Subject: Re: [PATCH v3 1/5] UefiCpuPkg/SmmBaseHob.h: Add SMM Base HOB Data
Date: Sun, 29 Jan 2023 05:24:31 +0000 [thread overview]
Message-ID: <MN0PR11MB61589152D34C9566C7F16D53FED29@MN0PR11MB6158.namprd11.prod.outlook.com> (raw)
In-Reply-To: <8142cc40-ca21-2748-a3de-d0432ccbdc07@redhat.com>
Thanks Gerd raise this open -- how to support more processors due to hob size limitation.
Looks multiple hobs is the only way since we have to store each cpu's info? Sorry, allow me ask a stupid question: why DataLength in hob defined as UINT16 causing the hob size limitation? Any design background here?
For smbase case:
I doubt CpuIndex is really required, because we can't avoid define another hob, and we can't avoid add statement for each hob cpu ranges (0 - 8191, 8192 - 16382,...), then what's meaning for the CpuIndex, we don't expect hob producer create smaller granularity CPU ranges that one hob CpuIndex associate with previous NumberOfCpus. With above consideration, I prefer keep existing patch as is, but only add statement gSmmBaseHobGuid only support max 8191 processes (which means to fix the CPU range for each hob)?
Thanks,
Jiaxin
> -----Original Message-----
> From: Laszlo Ersek <lersek@redhat.com>
> Sent: Friday, January 20, 2023 4:21 PM
> To: Ni, Ray <ray.ni@intel.com>; Gerd Hoffmann <kraxel@redhat.com>; Wu,
> Jiaxin <jiaxin.wu@intel.com>
> Cc: devel@edk2.groups.io; Dong, Eric <eric.dong@intel.com>; Zeng, Star
> <star.zeng@intel.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>; Kinney,
> Michael D <michael.d.kinney@intel.com>; Zimmer, Vincent
> <vincent.zimmer@intel.com>
> Subject: Re: [PATCH v3 1/5] UefiCpuPkg/SmmBaseHob.h: Add SMM Base
> HOB Data
>
> On 1/18/23 16:06, Ni, Ray wrote:
>
> > #pragma pack(1)
> > typedef struct {
> > UINT32 CpuIndex;
> > UINT32 NumberOfCpus; // align to
> EFI_SEC_PLATFORM_INFORMATION_RECORD2.NumberOfCpus
> > UINT64 SmBase[];
> > } SMM_BASE_HOB_DATA;
> > #pragma pack()
> >
> > For system with less than 8K CPUs, one HOB is produced. CpuIndex is set to
> 0 indicating
> > the HOB describes the CPU from 0 to NumberOfCpus-1.
> >
> > The HOB list may contains multiple such HOB instances each describing the
> information for
> > CPU from CpuIndex to CpuIndex + NumberOfCpus - 1.
> > The instance order in the HOB list is random so consumer cannot assume
> the CpuIndex
> > of first instance is 0.
>
> When using discontiguous blocks that are limited to ~64KB each:
>
> - The consumer won't be able to access elements of the "conceptual" big
> array in a truly random (= random-access) fashion. There won't be a
> single contiguous domain of valid subscripts. It's "bank switching", and
> switching banks should be avoided IMO. It effectively replaces the
> vector data structure with a linked list. The consequence is that the
> consumer will have to either (a) build a new (temporary, or permanent)
> index table of sorts, for implementing the "conceptual" big array as a
> factual contiguous array, or (b) traverse the HOB list multiple times.
>
> - If the element size of the array increases (which is otherwise
> possible to do compatibly, e.g. by placing a GUID and/or revision# in
> the HOB), the number of elements that fit in a single HOB decreases. I
> think that's an artifact that needlessly complicates debugging, and
> maybe performance too (it might increase the number of full-list
> traversals).
>
> - With relatively many elements fitting into a single HOB, on most
> platforms, just one HOB is going to be used. While that may be good for
> performance, it is not good for code coverage (testing). The quirky
> indexing method will not be exercised by most platforms.
>
> What's wrong with:
>
> - restricting the creation of all such HOBs after
> "gEfiPeiMemoryDiscoveredPpiGuid"
>
> - using a page allocation, for representing the array contiguously
>
> - in the HOB, only storing the address of the page allocation.
>
> Page allocations performed after gEfiPeiMemoryDiscoveredPpiGuid will not
> be moved, so the address in the HOB would be stable.
>
> Laszlo
next prev parent reply other threads:[~2023-01-29 5:24 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-18 9:56 [PATCH v3 0/5] Simplify SMM Relocation Process Wu, Jiaxin
2023-01-18 9:56 ` [PATCH v3 1/5] UefiCpuPkg/SmmBaseHob.h: Add SMM Base HOB Data Wu, Jiaxin
2023-01-18 11:19 ` Gerd Hoffmann
2023-01-18 15:06 ` Ni, Ray
2023-01-19 7:13 ` Gerd Hoffmann
2023-01-29 5:08 ` Wu, Jiaxin
2023-02-01 13:02 ` Gerd Hoffmann
2023-01-20 8:21 ` Laszlo Ersek
2023-01-29 5:24 ` Wu, Jiaxin [this message]
2023-02-01 13:14 ` Gerd Hoffmann
2023-02-02 0:44 ` Wu, Jiaxin
2023-02-02 3:54 ` [edk2-devel] " Ni, Ray
2023-02-02 3:52 ` Ni, Ray
2023-02-02 12:51 ` Gerd Hoffmann
2023-02-02 22:29 ` [edk2-devel] " Brian J. Johnson
2023-02-03 3:14 ` Ni, Ray
2023-02-03 7:54 ` Gerd Hoffmann
2023-02-03 13:22 ` Wu, Jiaxin
2023-02-03 13:31 ` Ni, Ray
2023-02-03 15:00 ` Gerd Hoffmann
2023-01-18 9:56 ` [PATCH v3 2/5] UefiCpuPkg/PiSmmCpuDxeSmm: Fix invalid InitializeMpSyncData call Wu, Jiaxin
2023-01-18 9:56 ` [PATCH v3 3/5] UefiCpuPkg/PiSmmCpuDxeSmm: Consume SMM Base Hob for SmBase info Wu, Jiaxin
2023-01-18 12:02 ` Gerd Hoffmann
2023-01-29 6:14 ` [edk2-devel] " Wu, Jiaxin
2023-01-18 9:56 ` [PATCH v3 4/5] UefiCpuPkg/SmmCpuFeaturesLib: Skip SMBASE configuration Wu, Jiaxin
2023-01-18 9:56 ` [PATCH v3 5/5] OvmfPkg/SmmCpuFeaturesLib: " Wu, Jiaxin
2023-01-18 12:19 ` Gerd Hoffmann
2023-01-18 14:37 ` Ni, Ray
2023-01-19 7:53 ` Gerd Hoffmann
2023-01-29 5:47 ` Wu, Jiaxin
2023-02-01 13:40 ` Gerd Hoffmann
2023-02-02 1:41 ` Wu, Jiaxin
2023-02-02 9:00 ` Gerd Hoffmann
2023-02-02 11:47 ` Laszlo Ersek
2023-02-02 12:24 ` Gerd Hoffmann
2023-02-03 3:05 ` Wu, Jiaxin
2023-02-03 2:47 ` Wu, Jiaxin
2023-02-03 3:45 ` Ni, Ray
2023-02-03 7:31 ` Gerd Hoffmann
2023-02-03 7:43 ` Ni, Ray
2023-02-03 8:49 ` Gerd Hoffmann
2023-02-03 11:18 ` Wu, Jiaxin
[not found] ` <173B5EAF72B992BD.14781@groups.io>
2023-02-03 8:59 ` [edk2-devel] " Wu, Jiaxin
2023-02-03 9:04 ` Gerd Hoffmann
2023-02-03 11:15 ` Wu, Jiaxin
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