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authorWill Deacon <will.deacon@arm.com>2017-03-10 20:32:25 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2017-03-20 16:25:45 +0000
commit87da236ebc711644dcff2339ee5b854f1abf1fca (patch)
tree73da290dd0092c7b537ee5c77476bd9d216bcf53 /arch/arm64/kvm
parentarm64: cache: Identify VPIPT I-caches (diff)
downloadlinux-dev-87da236ebc711644dcff2339ee5b854f1abf1fca.tar.xz
linux-dev-87da236ebc711644dcff2339ee5b854f1abf1fca.zip
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>
Diffstat (limited to 'arch/arm64/kvm')
-rw-r--r--arch/arm64/kvm/hyp/tlb.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/arch/arm64/kvm/hyp/tlb.c b/arch/arm64/kvm/hyp/tlb.c
index 9e1d2b75eecd..73464a96c365 100644
--- a/arch/arm64/kvm/hyp/tlb.c
+++ b/arch/arm64/kvm/hyp/tlb.c
@@ -94,6 +94,28 @@ void __hyp_text __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa)
dsb(ish);
isb();
+ /*
+ * If the host is running at EL1 and we have a VPIPT I-cache,
+ * then we must perform I-cache maintenance at EL2 in order for
+ * it to have an effect on the guest. Since the guest cannot hit
+ * I-cache lines allocated with a different VMID, we don't need
+ * to worry about junk out of guest reset (we nuke the I-cache on
+ * VMID rollover), but we do need to be careful when remapping
+ * executable pages for the same guest. This can happen when KSM
+ * takes a CoW fault on an executable page, copies the page into
+ * a page that was previously mapped in the guest and then needs
+ * to invalidate the guest view of the I-cache for that page
+ * from EL1. To solve this, we invalidate the entire I-cache when
+ * unmapping a page from a guest if we have a VPIPT I-cache but
+ * the host is running at EL1. As above, we could do better if
+ * we had the VA.
+ *
+ * The moral of this story is: if you have a VPIPT I-cache, then
+ * you should be running with VHE enabled.
+ */
+ if (!has_vhe() && icache_is_vpipt())
+ __flush_icache_all();
+
__tlb_switch_to_host()(kvm);
}