[v7,30/45] arm64: RME: Always use 4k pages for realms

Commit Message

Steven Price Feb. 13, 2025, 4:14 p.m. UTC

Always split up huge pages to avoid problems managing huge pages. There
are two issues currently:

1. The uABI for the VMM allows populating memory on 4k boundaries even
   if the underlying allocator (e.g. hugetlbfs) is using a larger page
   size. Using a memfd for private allocations will push this issue onto
   the VMM as it will need to respect the granularity of the allocator.

2. The guest is able to request arbitrary ranges to be remapped as
   shared. Again with a memfd approach it will be up to the VMM to deal
   with the complexity and either overmap (need the huge mapping and add
   an additional 'overlapping' shared mapping) or reject the request as
   invalid due to the use of a huge page allocator.

For now just break everything down to 4k pages in the RMM controlled
stage 2.

Signed-off-by: Steven Price <[e-mail]>
---
 arch/arm64/kvm/mmu.c | 4 ++++
 1 file changed, 4 insertions(+)

Patch

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 994e71cfb358..8c656a0ef4e9 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1641,6 +1641,10 @@  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (logging_active || is_protected_kvm_enabled()) {
 		force_pte = true;
 		vma_shift = PAGE_SHIFT;
+	} else if (vcpu_is_rec(vcpu)) {
+		// Force PTE level mappings for realms
+		force_pte = true;
+		vma_shift = PAGE_SHIFT;
 	} else {
 		vma_shift = get_vma_page_shift(vma, hva);
 	}