[PATCH v3 1/3] KVM: arm64: Remove VPIPT I-cache handling

Marc Zyngier
2023-12-04T14:36:19Z

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

Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Marc Zyngier <maz@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