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sync: rvck #267: [Backport] KVM support THP and huge pages spliting for dirty logging #231

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sync: rvck #267: [Backport] KVM support THP and huge pages spliting for dirty logging #231
yechao-w wants to merge 19 commits into
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@yechao-w yechao-w commented May 25, 2026

Sync commits from rvck PR 267.
Source PR: RVCK-Project/rvck#267

补丁冲突:

上游补丁: 03dc00a2b67854604c0aa8cbd32105f8b633451e “riscv: Support huge pfnmaps” 在THP开启的情况下,默认开启ARCH_SUPPORTS_HUGE_PFNMAP配置。此开关和olk版本中的自研功能: https://gitee.com/src-openeuler/kernel/issues/ID4NL4 有冲突,具体表现为 923e224 “mm: introduce remap_pfn_range_try_pmd() for PMD-level hugepage mapping” 引入了pte_clrhuge函数,此函数在riscv架构上缺少定义,导致编译失败。

冲突修改:
参照 cee7684 "pgtable: add pte_clrhuge() implementation for arm64",在riscv下实现pte_clrhuge函数。由于此函数为pte_mkhuge的反向操作,riscv上pte_mkhuge未做任何操作,所以pte_clrhuge实现也是直接返回pte即可。参见补丁集中第13个补丁:
riscv: pgtable: add pte_clrhuge() implementation for riscv

avpatel and others added 19 commits May 25, 2026 16:16
mainline inclusion
from mainline-6.17-rc1
commit 4a50578
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The kvm_riscv_vcpu_alloc_vector_context() does return an error code
upon failure so don't ignore this in kvm_arch_vcpu_create().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-2-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit 7c67de2
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The kvm_riscv_vcpu_aia_init() does not return any failure so drop
the return value which is always zero.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-3-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit b79bf20
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The kvm_riscv_local_tlb_sanitize() deals with sanitizing current
VMID related TLB mappings when a VCPU is moved from one host CPU
to another.

Let's move kvm_riscv_local_tlb_sanitize() to VMID management
sources and rename it to kvm_riscv_gstage_vmid_sanitize().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-4-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit 7584eb6
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The KVM_REQ_HFENCE_GVMA_VMID_ALL is same as KVM_REQ_TLB_FLUSH so
to avoid confusion let's replace KVM_REQ_HFENCE_GVMA_VMID_ALL with
KVM_REQ_TLB_FLUSH. Also, rename kvm_riscv_hfence_gvma_vmid_all_process()
to kvm_riscv_tlb_flush_process().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-5-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit eaa98ba
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The gstage_set_pte() and gstage_op_pte() should flush TLB only when
a leaf PTE changes so that unnecessary TLB flushes can be avoided.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-6-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit ca539ba
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The kvm_arch_flush_remote_tlbs_range() expected by KVM core can be
easily implemented for RISC-V using kvm_riscv_hfence_gvma_vmid_gpa()
hence provide it.

Also with kvm_arch_flush_remote_tlbs_range() available for RISC-V, the
mmu_wp_memory_region() can happily use kvm_flush_remote_tlbs_memslot()
instead of kvm_flush_remote_tlbs().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-7-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit 77ba646
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The H-extension CSRs accessed by kvm_riscv_vcpu_trap_redirect() will
trap when KVM RISC-V is running as Guest/VM hence remove these traps
by using ncsr_xyz() instead of csr_xyz().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-8-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit 4ecbd3e
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The MMU, TLB, and VMID management for KVM RISC-V already exists as
seprate sources so create separate headers along these lines. This
further simplifies asm/kvm_host.h header.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-9-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit f035b44
category: feature
bugzilla: RVCK-Project#257

--------------------------------

Introduce struct kvm_gstage_mapping which represents a g-stage
mapping at a particular g-stage page table level. Also, update
the kvm_riscv_gstage_map() to return the g-stage mapping upon
success.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-10-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit 4c933f3
category: feature
bugzilla: RVCK-Project#257

--------------------------------

Currently, the struct kvm_riscv_hfence does not have vmid field
and various hfence processing functions always pick vmid assigned
to the guest/VM. This prevents us from doing hfence operation on
arbitrary vmid hence add vmid field to struct kvm_riscv_hfence
and use it wherever applicable.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-11-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit dd82e35
category: feature
bugzilla: RVCK-Project#257

--------------------------------

The upcoming nested virtualization can share g-stage page table
management with the current host g-stage implementation hence
factor-out g-stage page table management as separate sources
and also use "kvm_riscv_mmu_" prefix for host g-stage functions.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-12-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.17-rc1
commit 1f6d0ee
category: feature
bugzilla: RVCK-Project#257

--------------------------------

Currently, all kvm_riscv_hfence_xyz() APIs assume VMID to be the
host VMID of the Guest/VM which resticts use of these APIs only
for host TLB maintenance. Let's allow passing VMID as a parameter
to all kvm_riscv_hfence_xyz() APIs so that they can be re-used
for nested virtualization related TLB maintenance.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Nutty Liu <liujingqi@lanxincomputing.com>
Link: https://lore.kernel.org/r/20250618113532.471448-13-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
category: feature
bugzilla: RVCK-Project#257

--------------------------------

This function provides the inverse operation of pte_mkhuge().

Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-6.15-rc1
commit 03dc00a
category: feature
bugzilla: RVCK-Project#257

--------------------------------

Use RSW0 as the special bit for pmds and puds, just like for ptes.
Also define the {pte,pmd,pud}_pgprot helpers which were previously
missing and are needed for the follow_pfnmap APIs.

Signed-off-by: Andrew Bresticker <abrestic@rivosinc.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250108135700.2614848-1-abrestic@rivosinc.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-7.0-rc1
commit ed7ae7a
category: feature
bugzilla: RVCK-Project#257

--------------------------------

Use block mapping if backed by a THP, as implemented in architectures
like ARM and x86_64.

Signed-off-by: Jessica Liu <liu.xuemei1@zte.com.cn>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251127165137780QbUOVPKPAfWSGAFl5qtRy@zte.com.cn
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
mainline inclusion
from mainline-v7.0-rc4
commit b342166
category: feature
bugzilla: RVCK-Project#257

--------------------------------

When dirty logging is enabled, guest stage mappings are forced to
PAGE_SIZE granularity. Changing the mapping page size at this point
is incorrect.

Fixes: ed7ae7a34bea ("RISC-V: KVM: Transparent huge page support")
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260226191231140_X1Juus7s2kgVlc0ZyW_K@zte.com.cn
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
…ging

mainline inclusion
from mainline-7.1-rc1
commit a216e24
category: feature
bugzilla: RVCK-Project#257

--------------------------------

When enabling dirty log in small chunks (e.g., QEMU default chunk
size of 256K), the chunk size is always smaller than the page size
of huge pages (1G or 2M) used in the gstage page tables. This caused
the write protection to be incorrectly skipped for huge PTEs because
the condition `(end - addr) >= page_size` was not satisfied.

Remove the size check in `kvm_riscv_gstage_wp_range()` to ensure huge
PTEs are always write-protected regardless of the chunk size. Additionally,
explicitly align the address down to the page size before invoking
`kvm_riscv_gstage_op_pte()` to guarantee that the address passed to the
operation function is page-aligned.

This fixes the issue where dirty pages might not be tracked correctly
when using huge pages.

Fixes: 9d05c1f ("RISC-V: KVM: Implement stage2 page table programming")
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/202603301610527120YZ-pAJY6x9SBpSRo1Wg4@zte.com.cn
Signed-off-by: Anup Patel <anup@brainfault.org>
mainline inclusion
from mainline-7.1-rc1
commit 6ad36f3
category: feature
bugzilla: RVCK-Project#257

--------------------------------

During dirty logging, all huge pages are write-protected. When the guest
writes to a write-protected huge page, a page fault is triggered. Before
recovering the write permission, the huge page must be split into smaller
pages (e.g., 4K). After splitting, the normal mapping process proceeds,
allowing write permission to be restored at the smaller page granularity.

If dirty logging is disabled because migration failed or was cancelled,
only recover the write permission at the 4K level, and skip recovering the
huge page mapping at this time to avoid the overhead of freeing page tables.
The huge page mapping can be recovered in the ioctl context, similar to x86,
in a later patch.

Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/202603301612587174XZ6QMCrymBqv30S6BN50@zte.com.cn
Signed-off-by: Anup Patel <anup@brainfault.org>
mainline inclusion
from mainline-7.0-rc4
commit dec9ed9
category: feature
bugzilla: RVCK-Project#257

--------------------------------

While fuzzing KVM on RISC-V, a use-after-free was observed in
kvm_riscv_gstage_get_leaf(),  where ptep_get() dereferences a
freed gstage page table page during gfn unmap.

The crash manifests as:
  use-after-free in ptep_get include/linux/pgtable.h:340 [inline]
  use-after-free in kvm_riscv_gstage_get_leaf arch/riscv/kvm/gstage.c:89
  Call Trace:
    ptep_get include/linux/pgtable.h:340 [inline]
    kvm_riscv_gstage_get_leaf+0x2ea/0x358 arch/riscv/kvm/gstage.c:89
    kvm_riscv_gstage_unmap_range+0xf0/0x308 arch/riscv/kvm/gstage.c:265
    kvm_unmap_gfn_range+0x168/0x1fc arch/riscv/kvm/mmu.c:256
    kvm_mmu_unmap_gfn_range virt/kvm/kvm_main.c:724 [inline]
  page last free pid 808 tgid 808 stack trace:
    kvm_riscv_mmu_free_pgd+0x1b6/0x26a arch/riscv/kvm/mmu.c:457
    kvm_arch_flush_shadow_all+0x1a/0x24 arch/riscv/kvm/mmu.c:134
    kvm_flush_shadow_all virt/kvm/kvm_main.c:344 [inline]

The UAF is caused by gstage page table walks running concurrently with
gstage pgd teardown. In particular, kvm_unmap_gfn_range() can traverse
gstage page tables while kvm_arch_flush_shadow_all() frees the pgd,
leading to use-after-free of page table pages.

Fix the issue by serializing gstage unmap and pgd teardown with
kvm->mmu_lock. Holding mmu_lock ensures that gstage page tables
remain valid for the duration of unmap operations and prevents
concurrent frees.

This matches existing RISC-V KVM usage of mmu_lock to protect gstage
map/unmap operations, e.g. kvm_riscv_mmu_iounmap.

Fixes: dd82e35638d67f ("RISC-V: KVM: Factor-out g-stage page table management")
Signed-off-by: Jiakai Xu <xujiakai2025@iscas.ac.cn>
Signed-off-by: Jiakai Xu <jiakaiPeanut@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260202040059.1801167-1-xujiakai2025@iscas.ac.cn
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Wang Yechao <wang.yechao255@zte.com.cn>
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github-actions Bot commented May 25, 2026


开始测试 log: https://github.com/RVCK-Project/rvck-olk/actions/runs/26392473868

参数解析结果
args value
repository RVCK-Project/rvck-olk
head ref pull/231/head
base ref OLK-6.6
LAVA repo RVCK-Project/lavaci
LAVA hardware ['qemu', 'lpi4a', 'sg2042', 'k1']
LAVA Testcase path lava-testcases/common-test/ltp/ltp.yaml
need run job kunit-test,kernel-build,check-patch,lava-trigger

测试完成

详细结果:
check result
kunit-test failure
kernel-build success
check-patch failure
lava-trigger-qemu failure
lava-trigger-sg2042 success
lava-trigger-k1 failure
lava-trigger-lpi4a failure

Kunit Test Result

kunit test failed

Kernel Build Result

Check Patch Result

Total Errors 1
Total Warnings 22

LAVA Check (qemu)

args value
testcase_repo RVCK-Project/lavaci
lava_template lava-job-template/qemu/qemu-ltp.yaml
testcase_path lava-testcases/common-test/ltp/ltp.yaml
kernel_download_url http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck-olk/231_26392473868_1/Image
initramfs_download_url http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck-olk/231_26392473868_1/initramfs.img
rootfs_download_url https://fast-mirror.isrc.ac.cn/openeuler-sig-riscv/openEuler-RISC-V/RVCK/openEuler24.03-LTS-SP1/openeuler-rootfs.img.zst
testcase_ref main
testitem_name RVCK-Project_rvck-olk_pull_request_target_231__common-test_qemu

result: Lava check fail!

LAVA Check (sg2042)

args value
testcase_repo RVCK-Project/lavaci
lava_template lava-job-template/sg2042/sg2042-ltp.yaml
testcase_path lava-testcases/common-test/ltp/ltp.yaml
kernel_download_url http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck-olk/231_26392473868_1/Image
initramfs_download_url http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck-olk/231_26392473868_1/initramfs.img
rootfs_download_url https://fast-mirror.isrc.ac.cn/openeuler-sig-riscv/openEuler-RISC-V/RVCK/openEuler24.03-LTS-SP1/openeuler-rootfs.tar.gz
testcase_ref main
testitem_name RVCK-Project_rvck-olk_pull_request_target_231__common-test_sg2042

result: Lava check done!

LAVA Check (spacemit-k1-bananapi-f3)

args value
testcase_repo RVCK-Project/lavaci
lava_template lava-job-template/spacemit-k1-bananapi-f3/k1-bpif3-ltp.yaml
testcase_path lava-testcases/common-test/ltp/ltp.yaml
kernel_download_url http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck-olk/231_26392473868_1/Image
initramfs_download_url http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck-olk/231_26392473868_1/initramfs.img
rootfs_download_url https://fast-mirror.isrc.ac.cn/openeuler-sig-riscv/openEuler-RISC-V/RVCK/openEuler24.03-LTS-SP1/openeuler-rootfs.tar.gz
testcase_ref main
testitem_name RVCK-Project_rvck-olk_pull_request_target_231__common-test_spacemit-k1-bananapi-f3

result: Lava check fail!

LAVA Check (lpi4a)

args value
testcase_repo RVCK-Project/lavaci
lava_template lava-job-template/lpi4a/lpi4a-ltp.yaml
testcase_path lava-testcases/common-test/ltp/ltp.yaml
kernel_download_url http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck-olk/231_26392473868_1/Image
initramfs_download_url http://10.30.190.110/openEuler-RISC-V/RVCK/OERV-RVCI/RVCK-Project/rvck-olk/231_26392473868_1/initramfs.img
rootfs_download_url https://fast-mirror.isrc.ac.cn/openeuler-sig-riscv/openEuler-RISC-V/RVCK/openEuler24.03-LTS-SP1/openeuler-rootfs.tar.gz
testcase_ref main
testitem_name RVCK-Project_rvck-olk_pull_request_target_231__common-test_lpi4a

result: Lava check fail!

@ieiao
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ieiao commented May 26, 2026

经过验证,可以正常编译、qemu可以正常启动,以下为AI补充的技术细节。

在 arm64 架构中,pte_clrhuge 的主要作用是将一个可能包含“块”描述符(Block Descriptor)标志的页表项属性转换为适用于“页”描述符(Page Descriptor)的属性。这是因为在 arm64 的页表结构中:

  • 对于中间层(L0-L2),位 1 如果为 0,表示这是一个“块”(Block),即大页。
  • 对于底层(L3/PTE),位 1 必须为 1 才能表示这是一个有效的“页”(Page)。

当 mm/huge_memory.c 尝试将一个透明大页(THP)拆分为普通页时,它会从原来的 pmd 中提取保护位。在 arm64 上,如果直接把 pmd 的保护位赋给pte,由于位 1 为 0,该 pte 将是无效的。因此 pte_clrhuge 在 arm64 上会将位 1 置为 1。

而在 RISC-V 架构中,页表项(PTE)的格式在所有层级上都是一致的。一个 PTE 是否是大页,仅取决于它所在的页表层级以及是否设置了 R/W/X 位。在 RISC-V 中没有专门的“块”vs“页”的类型位需要转换。因此,在 RISC-V 上,pte_clrhuge 逻辑上应该是一个空操作(no-op),直接返回原 PTE 即可,这与 pte_mkhuge 在 RISC-V 中的实现是一致的。

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