[PATCH 03/10] arm: KVM: Add optimized PIPT icache flushing

Marc Zyngier
2017-10-09T15:20:25Z

Calling __cpuc_coherent_user_range to invalidate the icache on
a PIPT icache machine has some pointless overhead, as it starts
by cleaning the dcache to the PoU, while we're guaranteed to
have already cleaned it to the PoC.

As KVM is the only user of such a feature, let's implement some
ad-hoc cache flushing in kvm_mmu.h. Should it become useful to
other subsystems, it can be moved to a more global location.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm/include/asm/kvm_hyp.h | 2 ++
arch/arm/include/asm/kvm_mmu.h | 24 ++++++++++++++++++++++--
2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/kvm_hyp.h b/arch/arm/include/asm/kvm_hyp.h
index 14b5903f0224..ad541f9ecc78 100644
--- a/arch/arm/include/asm/kvm_hyp.h
+++ b/arch/arm/include/asm/kvm_hyp.h
@@ -69,6 +69,8 @@
#define HIFAR __ACCESS_CP15(c6, 4, c0, 2)
#define HPFAR __ACCESS_CP15(c6, 4, c0, 4)
#define ICIALLUIS __ACCESS_CP15(c7, 0, c1, 0)
+#define BPIALLIS __ACCESS_CP15(c7, 0, c1, 6)
+#define ICIMVAU __ACCESS_CP15(c7, 0, c5, 1)
#define ATS1CPR __ACCESS_CP15(c7, 0, c8, 0)
#define TLBIALLIS __ACCESS_CP15(c8, 0, c3, 0)
#define TLBIALL __ACCESS_CP15(c8, 0, c7, 0)
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index f553aa62d0c3..6773dcf21bff 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -37,6 +37,8 @@

#include <linux/highmem.h>
#include <asm/cacheflush.h>
+#include <asm/cputype.h>
+#include <asm/kvm_hyp.h>
#include <asm/pgalloc.h>
#include <asm/stage2_pgtable.h>

@@ -157,6 +159,8 @@ static inline void __coherent_icache_guest_page(struct kvm_vcpu *vcpu,
kvm_pfn_t pfn,
unsigned long size)
{
+ u32 iclsz;
+
/*
* If we are going to insert an instruction page and the icache is
* either VIPT or PIPT, there is a potential problem where the host
@@ -182,17 +186,33 @@ static inline void __coherent_icache_guest_page(struct kvm_vcpu *vcpu,
}

/* PIPT cache. As for the d-side, use a temporary kernel mapping. */
+ iclsz = 4 << (read_cpuid(CPUID_CACHETYPE) & 0xf);
+
while (size) {
void *va = kmap_atomic_pfn(pfn);
+ void *end = va + PAGE_SIZE;
+ void *addr = va;
+
+ do {
+ write_sysreg(addr, ICIMVAU);
+ addr += iclsz;
+ } while (addr < end);

- __cpuc_coherent_user_range((unsigned long)va,
- (unsigned long)va + PAGE_SIZE);
+ dsb(ishst);
+ isb();

size -= PAGE_SIZE;
pfn++;

kunmap_atomic(va);
}
+
+ /* Check if we need to invalidate the BTB */
+ if ((read_cpuid_ext(CPUID_EXT_MMFR1) >> 24) != 4) {
+ write_sysreg(0, BPIALLIS);
+ dsb(ishst);
+ isb();
+ }
}

static inline void __kvm_flush_dcache_pte(pte_t pte)
--
2.14.1