arm64: KVM: Add support for VPIPT I-caches

A VPIPT I-cache has two main properties:

1. Lines allocated into the cache are tagged by VMID and a lookup can
   only hit lines that were allocated with the current VMID.

2. I-cache invalidation from EL1/0 only invalidates lines that match the
   current VMID of the CPU doing the invalidation.

This can cause issues with non-VHE configurations, where the host runs
at EL1 and wants to invalidate I-cache entries for a guest running with
a different VMID. VHE is not affected, because the host runs at EL2 and
I-cache invalidation applies as expected.

This patch solves the problem by invalidating the I-cache when unmapping
a page at stage 2 on a system with a VPIPT I-cache but not running with
VHE enabled. Hopefully this is an obscure enough configuration that the
overhead isn't anything to worry about, although it does mean that the
by-range I-cache invalidation currently performed when mapping at stage
2 can be elided on such systems, because the I-cache will be clean for
the guest VMID following a rollover event.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index dc3624d8b9db..d2293d49f555 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -242,12 +242,13 @@ static inline void __coherent_cache_guest_page(struct kvm_vcpu *vcpu,
 
 	kvm_flush_dcache_to_poc(va, size);
 
-	if (!icache_is_aliasing()) {		/* PIPT */
-		flush_icache_range((unsigned long)va,
-				   (unsigned long)va + size);
-	} else {
+	if (icache_is_aliasing()) {
 		/* any kind of VIPT cache */
 		__flush_icache_all();
+	} else if (is_kernel_in_hyp_mode() || !icache_is_vpipt()) {
+		/* PIPT or VPIPT at EL2 (see comment in __kvm_tlb_flush_vmid_ipa) */
+		flush_icache_range((unsigned long)va,
+				   (unsigned long)va + size);
 	}
 }