rme
GPC faults
FROM arm-A spec D9.2 GPC faults
If any of the following apply to the PA input to the GPC, the access generates a Granule protection fault at Level 0:
The input is a Secure PA and the Effective value of GPCCR_EL3.SPAD is 1.
The input is a Non-secure PA and the Effective value of GPCCR_EL3.NSPAD is 1.
The input is a Realm PA and the Effective value of GPCCR_EL3.RLPAD is 1.
...
An access is not permitted by the GPT if it is made to a PA space not permitted according to the Granule Protection Information (GPI) value returned by the GPT lookup.
If an access is not permitted by the GPT, then the access generates a Granule protection fault at Level x, where x is the level of the GPT entry that the access was checked against.
如果一次访问所对应的物理地址空间（PA space）不被 GPT 查找返回的粒度保护信息 （GPI）允许，则该访问不被 GPT 允许。
如果某次访问不被 GPT 允许，那么该访问会在第 x 层产生 GPF（Granule protection fault），其中 x 是检查该访问所对应的 GPT 表项的层级。
GPCCR_EL3
FROM arm-A spec: "D24.2.50 GPCCR_EL3, Granule Protection Check Control Register (EL3)"
L0GPTSZ, bits [23:20]
Level 0 GPT entry size.
This field advertises the number of least-significant address bits protected by each entry in the level 0 GPT.
0b0000 30-bits. Each entry covers 1GB of address space.
0b0100 34-bits. Each entry covers 16GB of address space.
0b0110 36-bits. Each entry covers 64GB of address space.
0b1001 39-bits. Each entry covers 512GB of address space.
GPC, bit [16]
Granule Protection Check Enable.
0b0: Granule protection checks are disabled. Accesses are not prevented by this mechanism.
0b1: All accesses to physical address spaces are subject to granule protection checks, except for fetches of GPT information and accesses governed by the GPCCR_EL3.GPCP control.
所有对物理地址的访问都受限于
granule protection checks, 除了 fetch GPT information 和 访问 受 GPCCR_EL3.GPCP 管理的字段.
If any stage of translation is enabled, this bit is permitted to be cached in a TLB.
GPCP, bit [17]
0b0: GPC faults are all reported with a priority that is consistent with the GPC being performed on any access to physical address space.
GPC（Granule Protection Check）故障的报告优先级，与对所有物理地址空间访问执行 GPC 时保持一致。
0b1: A GPC fault for the fetch of a Table descriptor for a stage 2 translation table walk might not be generated or reported.
All other GPC faults are reported with a priority consistent with the GPC being performed on all accesses to physical address spaces.
当进行二级页表遍历（stage 2 translation table walk）时，如果是获取表描述符 （Table descriptor）的操作，可能不会生成或报告 GPC 故障。但其它所有类型的 GPC 故障，仍然会按照对所有物理地址空间访问执行 GPC 时的优先级进行报告。
PGS, bits [15:14]: Physical Granule size.
0b00: 4KB
0b01: 64KB
0b10: 16KB
SH, bits [13:12]
GPT fetch Shareability attribute
0b00 Non-shareable.
0b10 Outer Shareable.
0b11 Inner Shareable.
SPAD, bit [7]: Secure PA space Disable. This field controls access to the Secure PA space.
0b0: This control has no effect on accesses.
0b1: When granule protection checks are enabled, access to the Secure Physical Address space generates a Granule Protection fault.
NSPAD, bit [6]
Non-secure PA space Disable. This field controls access to the Non-secure PA space.
0b0: This control has no effect on accesses.
0b1: When granule protection checks are enabled, access to the Non-secure Physical Address space generates a Granule Protection fault.
RLPAD, bit [5]
Realm PA space Disable. This field controls access to the Realm PA space.
0b0 This control has no effect on accesses.
0b1 When granule protection checks are enabled, access to the Realm Physical Address space generates a Granule Protection fault.
PPS, bits [2:0]: Protected Physical Address Size.
The size of the memory region protected by GPTBR_EL3, in terms of the number of least-significant address bits.
PPS Meaning
0b000 32 bits, 4GB protected address space.
0b001 36 bits, 64GB protected address space.
0b010 40 bits, 1TB protected address space.
0b011 42 bits, 4TB protected address space.
0b100 44 bits, 16TB protected address space.
0b101 48 bits, 256TB protected address space.
0b110 52 bits, 4PB protected address space.
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