From c8631ea59b6523035ffb607634eef7bacc8947fe Mon Sep 17 00:00:00 2001 From: Raghavendra Rao Ananta Date: Sat, 5 Apr 2025 00:10:42 +0000 Subject: [PATCH] KVM: arm64: selftests: Explicitly set the page attrs to Inner-Shareable Atomic instructions such as 'ldset' in the guest have been observed to cause an EL1 data abort with FSC 0x35 (IMPLEMENTATION DEFINED fault (Unsupported Exclusive or Atomic access)) on Neoverse-N3. Per DDI0487L.a B2.2.6, atomic instructions are only architecturally guaranteed for Inner/Outer Shareable Normal Write-Back memory. For anything else the behavior is IMPLEMENTATION DEFINED and can lose atomicity, or, in this case, generate an abort. It would appear that selftests sets up the stage-1 mappings as Non Shareable, leading to the observed abort. Explicitly set the Shareability field to Inner Shareable for non-LPA2 page tables. Note that for the LPA2 page table format, translations for cacheable memory inherit the shareability attribute of the PTW, i.e. TCR_ELx.SH{0,1}. Suggested-by: Oliver Upton Signed-off-by: Raghavendra Rao Ananta Link: https://lore.kernel.org/r/20250405001042.1470552-3-rananta@google.com [oliver: Rephrase changelog] Signed-off-by: Oliver Upton --- tools/testing/selftests/kvm/include/arm64/processor.h | 1 + tools/testing/selftests/kvm/lib/arm64/processor.c | 3 +++ 2 files changed, 4 insertions(+) diff --git a/tools/testing/selftests/kvm/include/arm64/processor.h b/tools/testing/selftests/kvm/include/arm64/processor.h index 7d88ff22013a..b0fc0f945766 100644 --- a/tools/testing/selftests/kvm/include/arm64/processor.h +++ b/tools/testing/selftests/kvm/include/arm64/processor.h @@ -113,6 +113,7 @@ #define PMD_TYPE_TABLE BIT(1) #define PTE_TYPE_PAGE BIT(1) +#define PTE_SHARED (UL(3) << 8) /* SH[1:0], inner shareable */ #define PTE_AF BIT(10) #define PTE_ADDR_MASK(page_shift) GENMASK(47, (page_shift)) diff --git a/tools/testing/selftests/kvm/lib/arm64/processor.c b/tools/testing/selftests/kvm/lib/arm64/processor.c index da5802c8a59c..9d69904cb608 100644 --- a/tools/testing/selftests/kvm/lib/arm64/processor.c +++ b/tools/testing/selftests/kvm/lib/arm64/processor.c @@ -172,6 +172,9 @@ static void _virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, } pg_attr = PTE_AF | PTE_ATTRINDX(attr_idx) | PTE_TYPE_PAGE | PTE_VALID; + if (!use_lpa2_pte_format(vm)) + pg_attr |= PTE_SHARED; + *ptep = addr_pte(vm, paddr, pg_attr); }