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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>,
	Dave Martin <Dave.Martin@arm.com>
Subject: [PATCH v2 15/94] KVM: arm64: nv: Handle SPSR_EL2 specially
Date: Tue, 11 Feb 2020 17:48:19 +0000
Message-ID: <20200211174938.27809-16-maz@kernel.org> (raw)
In-Reply-To: <20200211174938.27809-1-maz@kernel.org>

SPSR_EL2 needs special attention when running nested on ARMv8.3:

If taking an exception while running at vEL2 (actually EL1), the
HW will update the SPSR_EL1 register with the EL1 mode. We need
to track this in order to make sure that accesses to the virtual
view of SPSR_EL2 is correct.

To do so, we place an illegal value in SPSR_EL1.M, and patch it
accordingly if required when accessing it.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_emulate.h | 45 ++++++++++++++++++++++++++++
 arch/arm64/kvm/sys_regs.c            | 23 ++++++++++++--
 2 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 486978d0346b..26552c8571cb 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -277,11 +277,51 @@ static inline bool is_hyp_ctxt(const struct kvm_vcpu *vcpu)
 	return __is_hyp_ctxt(&vcpu->arch.ctxt);
 }
 
+static inline u64 __fixup_spsr_el2_write(struct kvm_cpu_context *ctxt, u64 val)
+{
+	if (!__vcpu_el2_e2h_is_set(ctxt)) {
+		/*
+		 * Clear the .M field when writing SPSR to the CPU, so that we
+		 * can detect when the CPU clobbered our SPSR copy during a
+		 * local exception.
+		 */
+		val &= ~0xc;
+	}
+
+	return val;
+}
+
+static inline u64 __fixup_spsr_el2_read(const struct kvm_cpu_context *ctxt, u64 val)
+{
+	if (__vcpu_el2_e2h_is_set(ctxt))
+		return val;
+
+	/*
+	 * SPSR.M == 0 means the CPU has not touched the SPSR, so the
+	 * register has still the value we saved on the last write.
+	 */
+	if ((val & 0xc) == 0)
+		return ctxt->sys_regs[SPSR_EL2];
+
+	/*
+	 * Otherwise there was a "local" exception on the CPU,
+	 * which from the guest's point of view was being taken from
+	 * EL2 to EL2, although it actually happened to be from
+	 * EL1 to EL1.
+	 * So we need to fix the .M field in SPSR, to make it look
+	 * like EL2, which is what the guest would expect.
+	 */
+	return (val & ~0x0c) | CurrentEL_EL2;
+}
+
 static inline unsigned long vcpu_read_spsr(const struct kvm_vcpu *vcpu)
 {
 	if (vcpu_mode_is_32bit(vcpu))
 		return vcpu_read_spsr32(vcpu);
 
+	if (unlikely(vcpu_mode_el2(vcpu)))
+		return vcpu_read_sys_reg(vcpu, SPSR_EL2);
+
 	if (vcpu->arch.sysregs_loaded_on_cpu)
 		return read_sysreg_el1(SYS_SPSR);
 	else
@@ -295,6 +335,11 @@ static inline void vcpu_write_spsr(struct kvm_vcpu *vcpu, unsigned long v)
 		return;
 	}
 
+	if (unlikely(vcpu_mode_el2(vcpu))) {
+		vcpu_write_sys_reg(vcpu, v, SPSR_EL2);
+		return;
+	}
+
 	if (vcpu->arch.sysregs_loaded_on_cpu)
 		write_sysreg_el1(v, SYS_SPSR);
 	else
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 64be9f452ad6..8c7d3d410689 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -258,11 +258,14 @@ u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
 			goto memory_read;
 
 		/*
-		 * ELR_EL2 is special cased for now.
+		 * ELR_EL2 and SPSR_EL2 are special cased for now.
 		 */
 		switch (reg) {
 		case ELR_EL2:
 			return read_sysreg_el1(SYS_ELR);
+		case SPSR_EL2:
+			val = read_sysreg_el1(SYS_SPSR);
+			return __fixup_spsr_el2_read(&vcpu->arch.ctxt, val);
 		}
 
 		/*
@@ -319,6 +322,10 @@ void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
 		case ELR_EL2:
 			write_sysreg_el1(val, SYS_ELR);
 			return;
+		case SPSR_EL2:
+			val = __fixup_spsr_el2_write(&vcpu->arch.ctxt, val);
+			write_sysreg_el1(val, SYS_SPSR);
+			return;
 		}
 
 		/* No EL1 counterpart? We're done here.? */
@@ -1589,6 +1596,18 @@ static bool access_sp_el1(struct kvm_vcpu *vcpu,
 	return true;
 }
 
+static bool access_spsr_el2(struct kvm_vcpu *vcpu,
+			    struct sys_reg_params *p,
+			    const struct sys_reg_desc *r)
+{
+	if (p->is_write)
+		vcpu_write_sys_reg(vcpu, p->regval, SPSR_EL2);
+	else
+		p->regval = vcpu_read_sys_reg(vcpu, SPSR_EL2);
+
+	return true;
+}
+
 /*
  * Architected system registers.
  * Important: Must be sorted ascending by Op0, Op1, CRn, CRm, Op2
@@ -1899,7 +1918,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	{ SYS_DESC(SYS_VTCR_EL2), access_rw, reset_val, VTCR_EL2, 0 },
 
 	{ SYS_DESC(SYS_DACR32_EL2), NULL, reset_unknown, DACR32_EL2 },
-	{ SYS_DESC(SYS_SPSR_EL2), access_rw, reset_val, SPSR_EL2, 0 },
+	{ SYS_DESC(SYS_SPSR_EL2), access_spsr_el2, reset_val, SPSR_EL2, 0 },
 	{ SYS_DESC(SYS_ELR_EL2), access_rw, reset_val, ELR_EL2, 0 },
 	{ SYS_DESC(SYS_SP_EL1), access_sp_el1},
 
-- 
2.20.1

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  parent reply index

Thread overview: 104+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 17:48 [PATCH v2 00/94] KVM: arm64: ARMv8.3/8.4 Nested Virtualization support Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 01/94] KVM: arm64: Move __load_guest_stage2 to kvm_mmu.h Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 02/94] arm64: Add ARM64_HAS_NESTED_VIRT cpufeature Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 03/94] KVM: arm64: nv: Introduce nested virtualization VCPU feature Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 04/94] KVM: arm64: nv: Reset VCPU to EL2 registers if VCPU nested virt is set Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 05/94] KVM: arm64: nv: Allow userspace to set PSR_MODE_EL2x Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 06/94] KVM: arm64: nv: Add EL2 system registers to vcpu context Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 07/94] KVM: arm64: nv: Reset VMPIDR_EL2 and VPIDR_EL2 to sane values Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 08/94] KVM: arm64: nv: Add nested virt VCPU primitives for vEL2 VCPU state Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 09/94] KVM: arm64: nv: Support virtual EL2 exceptions Marc Zyngier
2020-02-17 12:52   ` Mark Rutland
2020-02-17 13:41     ` Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 10/94] KVM: arm64: nv: Inject HVC exceptions to the virtual EL2 Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 11/94] KVM: arm64: nv: Handle trapped ERET from " Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 12/94] KVM: arm64: nv: Add EL2->EL1 translation helpers Marc Zyngier
2020-02-17 14:56   ` Mark Rutland
2020-02-17 17:43     ` Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 13/94] KVM: arm64: nv: Refactor vcpu_{read,write}_sys_reg Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 14/94] KVM: arm64: nv: Handle virtual EL2 registers in vcpu_read/write_sys_reg() Marc Zyngier
2020-02-11 17:48 ` Marc Zyngier [this message]
2020-02-17 15:04   ` [PATCH v2 15/94] KVM: arm64: nv: Handle SPSR_EL2 specially Mark Rutland
2020-02-11 17:48 ` [PATCH v2 16/94] KVM: arm64: nv: Handle HCR_EL2.E2H specially Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 17/94] KVM: arm64: nv: Save/Restore vEL2 sysregs Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 18/94] KVM: arm64: nv: Emulate PSTATE.M for a guest hypervisor Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 19/94] KVM: arm64: nv: Trap EL1 VM register accesses in virtual EL2 Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 20/94] KVM: arm64: nv: Trap SPSR_EL1, ELR_EL1 and VBAR_EL1 from " Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 21/94] KVM: arm64: nv: Trap CPACR_EL1 access in " Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 22/94] KVM: arm64: nv: Handle PSCI call via smc from the guest Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 23/94] KVM: arm64: nv: Respect virtual HCR_EL2.TWX setting Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 24/94] KVM: arm64: nv: Respect virtual CPTR_EL2.{TFP, FPEN} settings Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 25/94] KVM: arm64: nv: Respect the virtual HCR_EL2.NV bit setting Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 26/94] KVM: arm64: nv: Respect virtual HCR_EL2.TVM and TRVM settings Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 27/94] KVM: arm64: nv: Respect the virtual HCR_EL2.NV1 bit setting Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 28/94] KVM: arm64: nv: Emulate EL12 register accesses from the virtual EL2 Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 29/94] KVM: arm64: nv: Forward debug traps to the nested guest Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 30/94] KVM: arm64: nv: Configure HCR_EL2 for nested virtualization Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 31/94] KVM: arm64: nv: Only toggle cache for virtual EL2 when SCTLR_EL2 changes Marc Zyngier
2020-02-17 15:13   ` Mark Rutland
2020-02-11 17:48 ` [PATCH v2 32/94] KVM: arm64: nv: Filter out unsupported features from ID regs Marc Zyngier
2020-02-17 15:17   ` Mark Rutland
2020-02-11 17:48 ` [PATCH v2 33/94] KVM: arm64: nv: Hide RAS from nested guests Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 34/94] KVM: arm64: nv: Use ARMv8.5-GTG to advertise supported Stage-2 page sizes Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 35/94] KVM: arm64: Check advertised Stage-2 page size capability Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 36/94] KVM: arm/arm64: nv: Factor out stage 2 page table data from struct kvm Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 37/94] KVM: arm64: nv: Support multiple nested Stage-2 mmu structures Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 38/94] KVM: arm64: nv: Implement nested Stage-2 page table walk logic Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 39/94] KVM: arm64: nv: Handle shadow stage 2 page faults Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 40/94] KVM: arm64: nv: Unmap/flush shadow stage 2 page tables Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 41/94] KVM: arm64: nv: Move last_vcpu_ran to be per s2 mmu Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 42/94] KVM: arm64: nv: Introduce sys_reg_desc.forward_trap Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 43/94] KVM: arm64: nv: Set a handler for the system instruction traps Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 44/94] KVM: arm64: nv: Trap and emulate AT instructions from virtual EL2 Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 45/94] KVM: arm64: nv: Trap and emulate TLBI " Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 46/94] KVM: arm64: nv: Fold guest's HCR_EL2 configuration into the host's Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 47/94] KVM: arm64: nv: Handle traps for timer _EL02 and _EL2 sysregs accessors Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 48/94] KVM: arm64: nv: arch_timer: Support hyp timer emulation Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 49/94] KVM: arm64: nv: Propagate CNTVOFF_EL2 to the virtual EL1 timer Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 50/94] KVM: arm64: nv: Load timer before the GIC Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 51/94] KVM: arm64: nv: vgic-v3: Take cpu_if pointer directly instead of vcpu Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 52/94] KVM: arm64: nv: Nested GICv3 Support Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 53/94] KVM: arm64: nv: vgic: Emulate the HW bit in software Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 54/94] KVM: arm64: nv: vgic: Allow userland to set VGIC maintenance IRQ Marc Zyngier
2020-02-11 17:48 ` [PATCH v2 55/94] KVM: arm64: nv: Implement maintenance interrupt forwarding Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 56/94] KVM: arm64: nv: Add nested GICv3 tracepoints Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 57/94] arm64: KVM: nv: Add handling of EL2-specific timer registers Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 58/94] arm64: KVM: nv: Honor SCTLR_EL2.SPAN on entering vEL2 Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 59/94] arm64: KVM: nv: Handle SCTLR_EL2 RES0/RES1 bits Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 60/94] arm64: KVM: nv: Restrict S2 RD/WR permissions to match the guest's Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 61/94] arm64: KVM: nv: Allow userspace to request KVM_ARM_VCPU_NESTED_VIRT Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 62/94] arm64: Detect the ARMv8.4 TTL feature Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 63/94] arm64: KVM: nv: Add handling of ARMv8.4-TTL TLB invalidation Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 64/94] arm64: KVM: nv: Invalidate TLBs based on shadow S2 TTL-like information Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 65/94] arm64: KVM: nv: Tag shadow S2 entries with nested level Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 66/94] arm64: Add SW reserved PTE/PMD bits Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 67/94] arm64: Add level-hinted TLB invalidation helper Marc Zyngier
2020-03-25 10:38   ` Zhenyu Ye
2020-03-25 11:28     ` Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 68/94] arm64: KVM: Add a level hint to __kvm_tlb_flush_vmid_ipa Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 69/94] arm64: KVM: Use TTL hint in when invalidating stage-2 translations Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 70/94] arm64: KVM: nv: Add include containing the VNCR_EL2 offsets Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 71/94] KVM: arm64: Introduce accessor for ctxt->sys_reg Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 72/94] KVM: arm64: sysreg: Use ctxt_sys_reg() instead of raw sys_regs access Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 73/94] KVM: arm64: sve: Use __vcpu_sys_reg() " Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 74/94] KVM: arm64: pauth: Use ctxt_sys_reg() " Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 75/94] KVM: arm64: debug: " Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 76/94] KVM: arm64: Add missing reset handlers for PMU emulation Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 77/94] KVM: arm64: nv: Move sysreg reset check to boot time Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 78/94] KVM: arm64: Map VNCR-capable registers to a separate page Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 79/94] KVM: arm64: nv: Move nested vgic state into the sysreg file Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 80/94] KVM: arm64: Use accessors for timer ctl/cval/offset Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 81/94] KVM: arm64: Add VNCR-capable timer accessors for arm64 Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 82/94] KVM: arm64: Make struct kvm_regs userspace-only Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 83/94] KVM: arm64: VNCR-ize ELR_EL1 Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 84/94] KVM: arm64: VNCR-ize SP_EL1 Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 85/94] KVM: arm64: Disintegrate SPSR array Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 86/94] KVM: arm64: aarch32: Use __vcpu_sys_reg() instead of raw sys_regs access Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 87/94] KVM: arm64: VNCR-ize SPSR_EL1 Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 88/94] KVM: arm64: Add ARMv8.4 Enhanced Nested Virt cpufeature Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 89/94] KVM: arm64: nv: Synchronize PSTATE early on exit Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 90/94] KVM: arm64: nv: Sync nested timer state with ARMv8.4 Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 91/94] KVM: arm64: nv: Allocate VNCR page when required Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 92/94] KVM: arm64: nv: Enable ARMv8.4-NV support Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 93/94] KVM: arm64: nv: Fast-track 'InHost' exception returns Marc Zyngier
2020-02-11 17:49 ` [PATCH v2 94/94] KVM: arm64: nv: Fast-track EL1 TLBIs for VHE guests Marc Zyngier

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