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From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: Andre Przywara <andre.przywara@arm.com>,
	Christoffer Dall <christoffer.dall@arm.com>,
	Jintack Lim <jintack@cs.columbia.edu>,
	Haibo Xu <haibo.xu@linaro.org>, James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	kernel-team@android.com
Subject: [PATCH v4 66/66] KVM: arm64: nv: Fast-track EL1 TLBIs for VHE guests
Date: Mon, 10 May 2021 17:59:20 +0100	[thread overview]
Message-ID: <20210510165920.1913477-67-maz@kernel.org> (raw)
In-Reply-To: <20210510165920.1913477-1-maz@kernel.org>

Due to the way ARMv8.4-NV suppresses traps when accessing EL2
system registers, we can't track when the guest changes its
HCR_EL2.TGE setting. This means we always trap EL1 TLBIs,
even if they don't affect any guest.

This obviously has a huge impact on performance, as we handle
TLBI traps as a normal exit, and a normal VHE host issues
thousands of TLBIs when booting (and quite a few when running
userspace).

A cheap way to reduce the overhead is to handle the limited
case of {E2H,TGE}=={1,1} as a guest fixup, as we already have
the right mmu configuration in place. Just execute the decoded
instruction right away and return to the guest.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/hyp/vhe/switch.c | 36 +++++++++++++++++++++++++++++++++
 arch/arm64/kvm/hyp/vhe/tlb.c    |  6 ++++--
 arch/arm64/kvm/sys_regs.c       | 25 ++++++++---------------
 3 files changed, 48 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index b3e7d996b54d..67f8b7d89db6 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -166,6 +166,39 @@ void deactivate_traps_vhe_put(void)
 	__deactivate_traps_common();
 }
 
+static bool __hyp_handle_tlbi_el1(struct kvm_vcpu *vcpu)
+{
+	u32 instr;
+	u64 val;
+
+	/*
+	 * Ideally, we would never trap on EL1 TLB invalidations when the
+	 * guest's HCR_EL2.{E2H,TGE} == {1,1}. But "thanks" to ARMv8.4, we
+	 * don't trap writes to HCR_EL2, meaning that we can't track
+	 * changes to the virtual TGE bit. So we leave HCR_EL2.TTLB set on
+	 * the host. Oopsie...
+	 *
+	 * In order to speed-up EL1 TLBIs from the vEL2 guest when TGE is
+	 * set, try and handle these invalidation as quickly as possible,
+	 * without fully exiting (unless this needs forwarding).
+	 */
+	if (kvm_vcpu_trap_get_class(vcpu) != ESR_ELx_EC_SYS64 ||
+	    !vcpu_mode_el2(vcpu) ||
+	    (__vcpu_sys_reg(vcpu, HCR_EL2) & (HCR_E2H | HCR_TGE)) != (HCR_E2H | HCR_TGE))
+		return false;
+
+	instr = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu));
+	if (sys_reg_Op0(instr) != TLBI_Op0 ||
+	    sys_reg_Op1(instr) != TLBI_Op1_EL1)
+		return false;
+
+	val = vcpu_get_reg(vcpu, kvm_vcpu_sys_get_rt(vcpu));
+	__kvm_tlb_el1_instr(NULL, val, instr);
+	__kvm_skip_instr(vcpu);
+
+	return true;
+}
+
 static bool __hyp_handle_eret(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *ctxt = &vcpu->arch.ctxt;
@@ -259,6 +292,9 @@ static bool fixup_guest_exit_vhe(struct kvm_vcpu *vcpu, u64 *exit_code,
 	if (*exit_code == ARM_EXCEPTION_TRAP) {
 		if (__hyp_handle_eret(vcpu))
 			return true;
+
+		if (__hyp_handle_tlbi_el1(vcpu))
+			return true;
 	}
 
 	return fixup_guest_exit(vcpu, exit_code);
diff --git a/arch/arm64/kvm/hyp/vhe/tlb.c b/arch/arm64/kvm/hyp/vhe/tlb.c
index 001ac9f2f1b5..583255aa35ec 100644
--- a/arch/arm64/kvm/hyp/vhe/tlb.c
+++ b/arch/arm64/kvm/hyp/vhe/tlb.c
@@ -201,7 +201,8 @@ void __kvm_tlb_el1_instr(struct kvm_s2_mmu *mmu, u64 val, u64 sys_encoding)
 	dsb(ishst);
 
 	/* Switch to requested VMID */
-	__tlb_switch_to_guest(mmu, &cxt);
+	if (mmu)
+		__tlb_switch_to_guest(mmu, &cxt);
 
 	/*
 	 * Execute the same instruction as the guest hypervisor did,
@@ -240,5 +241,6 @@ void __kvm_tlb_el1_instr(struct kvm_s2_mmu *mmu, u64 val, u64 sys_encoding)
 	dsb(ish);
 	isb();
 
-	__tlb_switch_to_host(&cxt);
+	if (mmu)
+		__tlb_switch_to_host(&cxt);
 }
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 084230f6b993..6d0776737b76 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -2721,6 +2721,8 @@ static bool handle_tlbi_el1(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 			    const struct sys_reg_desc *r)
 {
 	u32 sys_encoding = sys_insn(p->Op0, p->Op1, p->CRn, p->CRm, p->Op2);
+	u64 virtual_vttbr = vcpu_read_sys_reg(vcpu, VTTBR_EL2);
+	struct kvm_s2_mmu *mmu;
 
 	/*
 	 * If we're here, this is because we've trapped on a EL1 TLBI
@@ -2739,24 +2741,13 @@ static bool handle_tlbi_el1(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 
 	mutex_lock(&vcpu->kvm->lock);
 
-	if ((__vcpu_sys_reg(vcpu, HCR_EL2) & (HCR_E2H | HCR_TGE)) != (HCR_E2H | HCR_TGE)) {
-		u64 virtual_vttbr = vcpu_read_sys_reg(vcpu, VTTBR_EL2);
-		struct kvm_s2_mmu *mmu;
-
-		mmu = lookup_s2_mmu(vcpu->kvm, virtual_vttbr, HCR_VM);
-		if (mmu)
-			__kvm_tlb_el1_instr(mmu, p->regval, sys_encoding);
+	mmu = lookup_s2_mmu(vcpu->kvm, virtual_vttbr, HCR_VM);
+	if (mmu)
+		__kvm_tlb_el1_instr(mmu, p->regval, sys_encoding);
 
-		mmu = lookup_s2_mmu(vcpu->kvm, virtual_vttbr, 0);
-		if (mmu)
-			__kvm_tlb_el1_instr(mmu, p->regval, sys_encoding);
-	} else {
-		/*
-		 * ARMv8.4-NV allows the guest to change TGE behind
-		 * our back, so we always trap EL1 TLBIs from vEL2...
-		 */
-		__kvm_tlb_el1_instr(&vcpu->kvm->arch.mmu, p->regval, sys_encoding);
-	}
+	mmu = lookup_s2_mmu(vcpu->kvm, virtual_vttbr, 0);
+	if (mmu)
+		__kvm_tlb_el1_instr(mmu, p->regval, sys_encoding);
 
 	mutex_unlock(&vcpu->kvm->lock);
 
-- 
2.29.2


  parent reply	other threads:[~2021-05-10 17:28 UTC|newest]

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-10 16:58 [PATCH v4 00/66] KVM: arm64: ARMv8.3/8.4 Nested Virtualization support Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 01/66] arm64: Add ARM64_HAS_NESTED_VIRT cpufeature Marc Zyngier
2021-05-20 13:32   ` Zenghui Yu
2021-05-10 16:58 ` [PATCH v4 02/66] KVM: arm64: nv: Introduce nested virtualization VCPU feature Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 03/66] KVM: arm64: nv: Reset VCPU to EL2 registers if VCPU nested virt is set Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 04/66] KVM: arm64: nv: Allow userspace to set PSR_MODE_EL2x Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 05/66] KVM: arm64: nv: Add EL2 system registers to vcpu context Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 06/66] KVM: arm64: nv: Add nested virt VCPU primitives for vEL2 VCPU state Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 07/66] KVM: arm64: nv: Handle HCR_EL2.NV system register traps Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 08/66] KVM: arm64: nv: Reset VMPIDR_EL2 and VPIDR_EL2 to sane values Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 09/66] KVM: arm64: nv: Support virtual EL2 exceptions Marc Zyngier
2021-05-20 12:55   ` Zenghui Yu
2021-05-10 16:58 ` [PATCH v4 10/66] KVM: arm64: nv: Inject HVC exceptions to the virtual EL2 Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 11/66] KVM: arm64: nv: Handle trapped ERET from " Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 12/66] KVM: arm64: nv: Add non-VHE-EL2->EL1 translation helpers Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 13/66] KVM: arm64: nv: Handle virtual EL2 registers in vcpu_read/write_sys_reg() Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 14/66] KVM: arm64: nv: Handle SPSR_EL2 specially Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 15/66] KVM: arm64: nv: Handle HCR_EL2.E2H specially Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 16/66] KVM: arm64: nv: Save/Restore vEL2 sysregs Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 17/66] KVM: arm64: nv: Emulate PSTATE.M for a guest hypervisor Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 18/66] KVM: arm64: nv: Trap EL1 VM register accesses in virtual EL2 Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 19/66] KVM: arm64: nv: Trap SPSR_EL1, ELR_EL1 and VBAR_EL1 from " Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 20/66] KVM: arm64: nv: Trap CPACR_EL1 access in " Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 21/66] KVM: arm64: nv: Handle PSCI call via smc from the guest Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 22/66] KVM: arm64: nv: Respect virtual HCR_EL2.TWX setting Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 23/66] KVM: arm64: nv: Respect virtual CPTR_EL2.{TFP,FPEN} settings Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 24/66] KVM: arm64: nv: Respect the virtual HCR_EL2.NV bit setting Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 25/66] KVM: arm64: nv: Respect virtual HCR_EL2.TVM and TRVM settings Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 26/66] KVM: arm64: nv: Respect the virtual HCR_EL2.NV1 bit setting Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 27/66] KVM: arm64: nv: Emulate EL12 register accesses from the virtual EL2 Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 28/66] KVM: arm64: nv: Forward debug traps to the nested guest Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 29/66] KVM: arm64: nv: Configure HCR_EL2 for nested virtualization Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 30/66] KVM: arm64: nv: Only toggle cache for virtual EL2 when SCTLR_EL2 changes Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 31/66] KVM: arm64: nv: Filter out unsupported features from ID regs Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 32/66] KVM: arm64: nv: Hide RAS from nested guests Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 33/66] KVM: arm64: nv: Support multiple nested Stage-2 mmu structures Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 34/66] KVM: arm64: nv: Implement nested Stage-2 page table walk logic Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 35/66] KVM: arm64: nv: Handle shadow stage 2 page faults Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 36/66] KVM: arm64: nv: Restrict S2 RD/WR permissions to match the guest's Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 37/66] KVM: arm64: nv: Unmap/flush shadow stage 2 page tables Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 38/66] KVM: arm64: nv: Introduce sys_reg_desc.forward_trap Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 39/66] KVM: arm64: nv: Set a handler for the system instruction traps Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 40/66] KVM: arm64: nv: Trap and emulate AT instructions from virtual EL2 Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 41/66] KVM: arm64: nv: Trap and emulate TLBI " Marc Zyngier
2021-07-14 16:40   ` Chase Conklin
2021-11-29 18:12     ` Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 42/66] KVM: arm64: nv: Fold guest's HCR_EL2 configuration into the host's Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 43/66] KVM: arm64: nv: arch_timer: Support hyp timer emulation Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 44/66] KVM: arm64: nv: Add handling of EL2-specific timer registers Marc Zyngier
2021-05-10 16:58 ` [PATCH v4 45/66] KVM: arm64: nv: Load timer before the GIC Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 46/66] KVM: arm64: nv: Nested GICv3 Support Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 47/66] KVM: arm64: nv: Don't load the GICv4 context on entering a nested guest Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 48/66] KVM: arm64: nv: vgic: Emulate the HW bit in software Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 49/66] KVM: arm64: nv: vgic: Allow userland to set VGIC maintenance IRQ Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 50/66] KVM: arm64: nv: Implement maintenance interrupt forwarding Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 51/66] KVM: arm64: nv: Add nested GICv3 tracepoints Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 52/66] KVM: arm64: nv: Allow userspace to request KVM_ARM_VCPU_NESTED_VIRT Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 53/66] KVM: arm64: nv: Add handling of ARMv8.4-TTL TLB invalidation Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 54/66] KVM: arm64: nv: Invalidate TLBs based on shadow S2 TTL-like information Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 55/66] KVM: arm64: Allow populating S2 SW bits Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 56/66] KVM: arm64: nv: Tag shadow S2 entries with nested level Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 57/66] KVM: arm64: nv: Add include containing the VNCR_EL2 offsets Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 58/66] KVM: arm64: Map VNCR-capable registers to a separate page Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 59/66] KVM: arm64: nv: Move nested vgic state into the sysreg file Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 60/66] KVM: arm64: Add ARMv8.4 Enhanced Nested Virt cpufeature Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 61/66] KVM: arm64: nv: Synchronize PSTATE early on exit Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 62/66] KVM: arm64: nv: Sync nested timer state with ARMv8.4 Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 63/66] KVM: arm64: nv: Allocate VNCR page when required Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 64/66] KVM: arm64: nv: Enable ARMv8.4-NV support Marc Zyngier
2021-05-10 16:59 ` [PATCH v4 65/66] KVM: arm64: nv: Fast-track 'InHost' exception returns Marc Zyngier
2021-05-10 16:59 ` Marc Zyngier [this message]
2021-06-03  7:07 ` [PATCH v4 00/66] KVM: arm64: ARMv8.3/8.4 Nested Virtualization support Jamie Iles
2021-06-03  8:39   ` Marc Zyngier
2021-06-03 11:08     ` Marc Zyngier
2021-06-07  9:59     ` Jamie Iles

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