[PATCH v2 1/3] KVM: arm64: Remove VPIPT I-cache handling

[Marc Zyngier]

We have some special handling for VPIPT I-cache in critical parts
of the cache and TLB maintenance. Remove it.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/include/asm/kvm_mmu.h |  7 ----
 arch/arm64/kvm/hyp/nvhe/pkvm.c   |  2 +-
 arch/arm64/kvm/hyp/nvhe/tlb.c    | 61 --------------------------------
 arch/arm64/kvm/hyp/vhe/tlb.c     | 13 -------
 4 files changed, 1 insertion(+), 82 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 49e0d4b36bd0..e3e793d0ec30 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -243,13 +243,6 @@ static inline size_t __invalidate_icache_max_range(void)
 
 static inline void __invalidate_icache_guest_page(void *va, size_t size)
 {
-	/*
-	 * VPIPT I-cache maintenance must be done from EL2. See comment in the
-	 * nVHE flavor of __kvm_tlb_flush_vmid_ipa().
-	 */
-	if (icache_is_vpipt() && read_sysreg(CurrentEL) != CurrentEL_EL2)
-		return;
-
 	/*
 	 * Blow the whole I-cache if it is aliasing (i.e. VIPT) or the
 	 * invalidation range exceeds our arbitrary limit on invadations by
diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index 9d23a51d7f75..b29f15418c0a 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -12,7 +12,7 @@
 #include <nvhe/pkvm.h>
 #include <nvhe/trap_handler.h>
 
-/* Used by icache_is_vpipt(). */
+/* Used by icache_is_aliasing(). */
 unsigned long __icache_flags;
 
 /* Used by kvm_get_vttbr(). */
diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c b/arch/arm64/kvm/hyp/nvhe/tlb.c
index 1b265713d6be..a60fb13e2192 100644
--- a/arch/arm64/kvm/hyp/nvhe/tlb.c
+++ b/arch/arm64/kvm/hyp/nvhe/tlb.c
@@ -105,28 +105,6 @@ void __kvm_tlb_flush_vmid_ipa(struct kvm_s2_mmu *mmu,
 	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 (icache_is_vpipt())
-		icache_inval_all_pou();
-
 	__tlb_switch_to_host(&cxt);
 }
 
@@ -157,28 +135,6 @@ void __kvm_tlb_flush_vmid_ipa_nsh(struct kvm_s2_mmu *mmu,
 	dsb(nsh);
 	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 (icache_is_vpipt())
-		icache_inval_all_pou();
-
 	__tlb_switch_to_host(&cxt);
 }
 
@@ -205,10 +161,6 @@ void __kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu,
 	dsb(ish);
 	isb();
 
-	/* See the comment in __kvm_tlb_flush_vmid_ipa() */
-	if (icache_is_vpipt())
-		icache_inval_all_pou();
-
 	__tlb_switch_to_host(&cxt);
 }
 
@@ -246,18 +198,5 @@ void __kvm_flush_vm_context(void)
 	/* Same remark as in __tlb_switch_to_guest() */
 	dsb(ish);
 	__tlbi(alle1is);
-
-	/*
-	 * VIPT and PIPT caches are not affected by VMID, so no maintenance
-	 * is necessary across a VMID rollover.
-	 *
-	 * VPIPT caches constrain lookup and maintenance to the active VMID,
-	 * so we need to invalidate lines with a stale VMID to avoid an ABA
-	 * race after multiple rollovers.
-	 *
-	 */
-	if (icache_is_vpipt())
-		asm volatile("ic ialluis");
-
 	dsb(ish);
 }
diff --git a/arch/arm64/kvm/hyp/vhe/tlb.c b/arch/arm64/kvm/hyp/vhe/tlb.c
index b636b4111dbf..b32e2940df7d 100644
--- a/arch/arm64/kvm/hyp/vhe/tlb.c
+++ b/arch/arm64/kvm/hyp/vhe/tlb.c
@@ -216,18 +216,5 @@ void __kvm_flush_vm_context(void)
 {
 	dsb(ishst);
 	__tlbi(alle1is);
-
-	/*
-	 * VIPT and PIPT caches are not affected by VMID, so no maintenance
-	 * is necessary across a VMID rollover.
-	 *
-	 * VPIPT caches constrain lookup and maintenance to the active VMID,
-	 * so we need to invalidate lines with a stale VMID to avoid an ABA
-	 * race after multiple rollovers.
-	 *
-	 */
-	if (icache_is_vpipt())
-		asm volatile("ic ialluis");
-
 	dsb(ish);
 }
-- 
2.39.2