Re: [PATCH v4 11/17] KVM: arm64: Filter out non-kernel addresses in kern_hyp_va
From: Fuad Tabba <fuad.tabba@linux.dev>
Date: 2026-08-18 14:46:12
Also in:
kvmarm
Hi Vincent, On Fri, 31 Jul 2026 at 15:36, Vincent Donnefort [off-list ref] wrote:
quoted hunk ↗ jump to hunk
kern_hyp_va() is idempotent for the hypervisor linear space. This is handy for nVHE hypervisor callers handling kvm_vcpu or kvm_arch pointers. Those pointers can originate from the hypervisor space (when protected mode is enabled, we don't trust the kernel and the hypervisor uses its own copy) or from the kernel space (we do trust the kernel in "non-protected" nVHE). This idempotence does not hold for addresses within the hypervisor private range, like the ones you get from the pKVM heap allocator (hyp_alloc()). To resolve this, filter out non-kernel addresses based on PAGE_OFFSET. Leave the assembly version untouched as it has no current users. Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev> Tested-by: Fuad Tabba <fuad.tabba@linux.dev> Signed-off-by: Vincent Donnefort <redacted>diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index 6eae7e7e2a68..d60e5f2de10c 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h@@ -126,6 +126,9 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v) * replace the instructions with `nop`s. */ #ifndef __KVM_VHE_HYPERVISOR__ + if (!is_ttbr1_addr(v)) + return v; +
I gave this a tag earlier and only came back to the cost side now, sorry. The check is unconditional, so plain nVHE pays it on every kern_hyp_va(), including the one in __kvm_vcpu_run(), and it has no private range to protect. Could it be gated on is_protected_kvm_enabled(), the same way patch 17 gates hyp_trace_buffer_alloc_bpages()? Cheers, /fuad
asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n" /* mask with va_mask */
"ror %0, %0, #1\n" /* rotate to the first tag bit */
"add %0, %0, #0\n" /* insert the low 12 bits of the tag */
--
2.55.0.508.g3f0d502094-goog