[PATCH v3 30/66] KVM: arm64: nv: Only toggle cache for virtual EL2 when SCTLR_EL2 changes

Marc Zyngier
2020-12-10T16:30:22Z

From: Christoffer Dall <christoffer.dall@linaro.org>

So far we were flushing almost the entire universe whenever a VM would
load/unload the SCTLR_EL1 and the two versions of that register had
different MMU enabled settings. This turned out to be so slow that it
prevented forward progress for a nested VM, because a scheduler timer
tick interrupt would always be pending when we reached the nested VM.

To avoid this problem, we consider the SCTLR_EL2 when evaluating if
caches are on or off when entering virtual EL2 (because this is the
value that we end up shadowing onto the hardware EL1 register).

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/kvm_mmu.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index e52d82aeadca..76a8a0ca45b8 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -125,6 +125,7 @@ alternative_cb_end
#include <asm/cache.h>
#include <asm/cacheflush.h>
#include <asm/mmu_context.h>
+#include <asm/kvm_emulate.h>

void kvm_update_va_mask(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst);
@@ -201,7 +202,10 @@ struct kvm;

static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu)
{
- return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101;
+ if (vcpu_mode_el2(vcpu))
+ return (__vcpu_sys_reg(vcpu, SCTLR_EL2) & 0b101) == 0b101;
+ else
+ return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101;
}

static inline void __clean_dcache_guest_page(kvm_pfn_t pfn, unsigned long size)
--
2.29.2