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From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>,
	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: Re: [PATCH 18/59] KVM: arm64: nv: Trap EL1 VM register accesses in virtual EL2
Date: Mon, 1 Jul 2019 17:12:23 +0100
Message-ID: <37c2b50d-7a5a-335a-ed5e-6d568ee94cb7@arm.com> (raw)
In-Reply-To: <20190621093843.220980-19-marc.zyngier@arm.com>


On 6/21/19 10:38 AM, Marc Zyngier wrote:
> From: Christoffer Dall <christoffer.dall@linaro.org>
>
> When running in virtual EL2 mode, we actually run the hardware in EL1
> and therefore have to use the EL1 registers to ensure correct operation.
>
> By setting the HCR.TVM and HCR.TVRM we ensure that the virtual EL2 mode
> doesn't shoot itself in the foot when setting up what it believes to be
> a different mode's system register state (for example when preparing to
> switch to a VM).
A guest hypervisor with vhe enabled uses the _EL12 register names when preparing
to run a guest, and accesses to those registers are already trapped when setting
HCR_EL2.NV. This patch affects only non-vhe guest hypervisors, would you mind
updating the message to reflect that?
>
> We can leverage the existing sysregs infrastructure to support trapped
> accesses to these registers.
>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/arm64/kvm/hyp/switch.c | 4 ++++
>  arch/arm64/kvm/sys_regs.c   | 7 ++++++-
>  2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 7b55c11b30fb..791b26570347 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -135,6 +135,10 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>  {
>  	u64 hcr = vcpu->arch.hcr_el2;
>  
> +	/* Trap VM sysreg accesses if an EL2 guest is not using VHE. */
> +	if (vcpu_mode_el2(vcpu) && !vcpu_el2_e2h_is_set(vcpu))
> +		hcr |= HCR_TVM | HCR_TRVM;
> +
>  	write_sysreg(hcr, hcr_el2);
>  
>  	if (cpus_have_const_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE))
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index e181359adadf..0464d8e29cba 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -440,7 +440,12 @@ static bool access_vm_reg(struct kvm_vcpu *vcpu,
>  	u64 val;
>  	int reg = r->reg;
>  
> -	BUG_ON(!p->is_write);
> +	BUG_ON(!vcpu_mode_el2(vcpu) && !p->is_write);
> +
> +	if (!p->is_write) {
> +		p->regval = vcpu_read_sys_reg(vcpu, reg);
> +		return true;
> +	}
>  
>  	/* See the 32bit mapping in kvm_host.h */
>  	if (p->is_aarch32)

For more context:

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e181359adadf..0464d8e29cba 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -428,31 +428,36 @@ static bool access_dcsw(struct kvm_vcpu *vcpu,
 }
 
 /*
  * Generic accessor for VM registers. Only called as long as HCR_TVM
  * is set. If the guest enables the MMU, we stop trapping the VM
  * sys_regs and leave it in complete control of the caches.
  */
 static bool access_vm_reg(struct kvm_vcpu *vcpu,
                          struct sys_reg_params *p,
                          const struct sys_reg_desc *r)
 {
        bool was_enabled = vcpu_has_cache_enabled(vcpu);
        u64 val;
        int reg = r->reg;
 
-       BUG_ON(!p->is_write);
+       BUG_ON(!vcpu_mode_el2(vcpu) && !p->is_write);
+
+       if (!p->is_write) {
+               p->regval = vcpu_read_sys_reg(vcpu, reg);
+               return true;
+       }
 
        /* See the 32bit mapping in kvm_host.h */
        if (p->is_aarch32)
                reg = r->reg / 2;
 
        if (!p->is_aarch32 || !p->is_32bit) {
                val = p->regval;
        } else {
                val = vcpu_read_sys_reg(vcpu, reg);
                if (r->reg % 2)
                        val = (p->regval << 32) | (u64)lower_32_bits(val);
                else
                        val = ((u64)upper_32_bits(val) << 32) |
                                lower_32_bits(p->regval);
        }

Perhaps the function comment should be updated to reflect that the function is
also used for VM register traps for a non-vhe guest hypervisor?

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  reply index

Thread overview: 177+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-21  9:37 [PATCH 00/59] KVM: arm64: ARMv8.3 Nested Virtualization support Marc Zyngier
2019-06-21  9:37 ` [PATCH 01/59] KVM: arm64: Migrate _elx sysreg accessors to msr_s/mrs_s Marc Zyngier
2019-06-24 11:16   ` Dave Martin
2019-06-24 12:59   ` Alexandru Elisei
2019-07-03 12:32     ` Marc Zyngier
2019-06-21  9:37 ` [PATCH 02/59] KVM: arm64: Move __load_guest_stage2 to kvm_mmu.h Marc Zyngier
2019-06-24 11:19   ` Dave Martin
2019-07-03  9:30     ` Marc Zyngier
2019-07-03 16:13       ` Dave Martin
2019-06-21  9:37 ` [PATCH 03/59] arm64: Add ARM64_HAS_NESTED_VIRT cpufeature Marc Zyngier
2019-06-21 13:08   ` Julien Thierry
2019-06-21 13:22     ` Marc Zyngier
2019-06-21 13:44   ` Suzuki K Poulose
2019-06-24 11:24   ` Dave Martin
2019-06-21  9:37 ` [PATCH 04/59] KVM: arm64: nv: Introduce nested virtualization VCPU feature Marc Zyngier
2019-06-21 13:08   ` Julien Thierry
2019-06-24 11:28   ` Dave Martin
2019-07-03 11:53     ` Marc Zyngier
2019-07-03 16:27       ` Dave Martin
2019-06-24 11:43   ` Dave Martin
2019-07-03 11:56     ` Marc Zyngier
2019-07-03 16:24       ` Dave Martin
2019-06-21  9:37 ` [PATCH 05/59] KVM: arm64: nv: Reset VCPU to EL2 registers if VCPU nested virt is set Marc Zyngier
2019-06-24 10:19   ` Suzuki K Poulose
2019-06-24 11:38   ` Dave Martin
2019-06-21  9:37 ` [PATCH 06/59] KVM: arm64: nv: Allow userspace to set PSR_MODE_EL2x Marc Zyngier
2019-06-21 13:24   ` Julien Thierry
2019-06-21 13:50     ` Marc Zyngier
2019-06-24 12:48       ` Dave Martin
2019-07-03  9:21         ` Marc Zyngier
2019-07-04 10:00           ` Dave Martin
2019-06-21  9:37 ` [PATCH 07/59] KVM: arm64: nv: Add EL2 system registers to vcpu context Marc Zyngier
2019-06-24 12:54   ` Dave Martin
2019-07-03 12:20     ` Marc Zyngier
2019-07-03 16:31       ` Dave Martin
2019-06-24 15:47   ` Alexandru Elisei
2019-07-03 13:20     ` Marc Zyngier
2019-07-03 16:01       ` Marc Zyngier
2019-07-01 16:36   ` Suzuki K Poulose
2019-06-21  9:37 ` [PATCH 08/59] KVM: arm64: nv: Reset VMPIDR_EL2 and VPIDR_EL2 to sane values Marc Zyngier
2019-06-24 12:59   ` Dave Martin
2019-06-21  9:37 ` [PATCH 09/59] KVM: arm64: nv: Add nested virt VCPU primitives for vEL2 VCPU state Marc Zyngier
2019-06-24 13:08   ` Dave Martin
2019-06-21  9:37 ` [PATCH 10/59] KVM: arm64: nv: Support virtual EL2 exceptions Marc Zyngier
2019-07-08 13:56   ` Steven Price
2019-06-21  9:37 ` [PATCH 11/59] KVM: arm64: nv: Inject HVC exceptions to the virtual EL2 Marc Zyngier
2019-06-25 13:13   ` Alexandru Elisei
2019-07-03 14:16     ` Marc Zyngier
2019-07-30 14:08     ` Alexandru Elisei
2019-06-21  9:37 ` [PATCH 12/59] KVM: arm64: nv: Handle trapped ERET from " Marc Zyngier
2019-07-02 12:00   ` Alexandru Elisei
2019-06-21  9:37 ` [PATCH 13/59] KVM: arm64: nv: Handle virtual EL2 registers in vcpu_read/write_sys_reg() Marc Zyngier
2019-06-24 12:42   ` Julien Thierry
2019-06-25 14:02     ` Alexandru Elisei
2019-07-03 12:15     ` Marc Zyngier
2019-07-03 15:21       ` Julien Thierry
2019-06-25 15:18   ` Alexandru Elisei
2019-07-01  9:58     ` Alexandru Elisei
2019-07-03 15:59     ` Marc Zyngier
2019-07-03 16:32       ` Alexandru Elisei
2019-07-04 14:39         ` Marc Zyngier
2019-06-26 15:04   ` Alexandru Elisei
2019-07-04 15:05     ` Marc Zyngier
2019-07-01 12:10   ` Alexandru Elisei
2019-06-21  9:37 ` [PATCH 14/59] KVM: arm64: nv: Handle SPSR_EL2 specially Marc Zyngier
2019-06-21  9:37 ` [PATCH 15/59] KVM: arm64: nv: Refactor vcpu_{read,write}_sys_reg Marc Zyngier
2019-06-24 15:07   ` Julien Thierry
2019-07-03 13:09     ` Marc Zyngier
2019-06-27  9:21   ` Alexandru Elisei
2019-07-04 15:15     ` Marc Zyngier
2019-06-21  9:38 ` [PATCH 16/59] KVM: arm64: nv: Save/Restore vEL2 sysregs Marc Zyngier
2019-06-25  8:48   ` Julien Thierry
2019-07-03 13:42     ` Marc Zyngier
2019-07-01 12:09   ` Alexandru Elisei
2019-08-21 11:57   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 17/59] KVM: arm64: nv: Emulate PSTATE.M for a guest hypervisor Marc Zyngier
2019-06-21  9:38 ` [PATCH 18/59] KVM: arm64: nv: Trap EL1 VM register accesses in virtual EL2 Marc Zyngier
2019-07-01 16:12   ` Alexandru Elisei [this message]
2019-06-21  9:38 ` [PATCH 19/59] KVM: arm64: nv: Trap SPSR_EL1, ELR_EL1 and VBAR_EL1 from " Marc Zyngier
2019-06-21  9:38 ` [PATCH 20/59] KVM: arm64: nv: Trap CPACR_EL1 access in " Marc Zyngier
2019-07-01 16:40   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 21/59] KVM: arm64: nv: Set a handler for the system instruction traps Marc Zyngier
2019-06-25 12:55   ` Julien Thierry
2019-07-03 14:15     ` Marc Zyngier
2019-06-21  9:38 ` [PATCH 22/59] KVM: arm64: nv: Handle PSCI call via smc from the guest Marc Zyngier
2019-06-21  9:38 ` [PATCH 23/59] KVM: arm64: nv: Respect virtual HCR_EL2.TWX setting Marc Zyngier
2019-06-25 14:19   ` Julien Thierry
2019-07-02 12:54     ` Alexandru Elisei
2019-07-03 14:18     ` Marc Zyngier
2019-06-21  9:38 ` [PATCH 24/59] KVM: arm64: nv: Respect virtual CPTR_EL2.TFP setting Marc Zyngier
2019-06-21  9:38 ` [PATCH 25/59] KVM: arm64: nv: Don't expose SVE to nested guests Marc Zyngier
2019-06-21  9:38 ` [PATCH 26/59] KVM: arm64: nv: Respect the virtual HCR_EL2.NV bit setting Marc Zyngier
2019-06-26  5:31   ` Julien Thierry
2019-07-03 16:31     ` Marc Zyngier
2019-06-21  9:38 ` [PATCH 27/59] KVM: arm64: nv: Respect virtual HCR_EL2.TVM and TRVM settings Marc Zyngier
2019-06-26  6:55   ` Julien Thierry
2019-07-04 14:57     ` Marc Zyngier
2019-06-21  9:38 ` [PATCH 28/59] KVM: arm64: nv: Respect the virtual HCR_EL2.NV1 bit setting Marc Zyngier
2019-06-26  7:23   ` Julien Thierry
2019-07-02 16:32   ` Alexandru Elisei
2019-07-03  9:10     ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 29/59] KVM: arm64: nv: Emulate EL12 register accesses from the virtual EL2 Marc Zyngier
2019-07-03  9:16   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 30/59] KVM: arm64: nv: Configure HCR_EL2 for nested virtualization Marc Zyngier
2019-06-21  9:38 ` [PATCH 31/59] KVM: arm64: nv: Only toggle cache for virtual EL2 when SCTLR_EL2 changes Marc Zyngier
2019-06-21  9:38 ` [PATCH 32/59] KVM: arm64: nv: Hide RAS from nested guests Marc Zyngier
2019-07-03 13:59   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 33/59] KVM: arm64: nv: Pretend we only support larger-than-host page sizes Marc Zyngier
2019-07-03 14:13   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 34/59] KVM: arm/arm64: nv: Factor out stage 2 page table data from struct kvm Marc Zyngier
2019-07-03 15:52   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 35/59] KVM: arm/arm64: nv: Support multiple nested stage 2 mmu structures Marc Zyngier
2019-06-25 12:19   ` Alexandru Elisei
2019-07-03 13:47     ` Marc Zyngier
2019-06-27 13:15   ` Julien Thierry
2019-07-04 15:51   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 36/59] KVM: arm64: nv: Implement nested Stage-2 page table walk logic Marc Zyngier
2019-06-21  9:38 ` [PATCH 37/59] KVM: arm64: nv: Handle shadow stage 2 page faults Marc Zyngier
2019-07-05 14:28   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 38/59] KVM: arm64: nv: Unmap/flush shadow stage 2 page tables Marc Zyngier
2019-07-01  8:03   ` Julien Thierry
2019-06-21  9:38 ` [PATCH 39/59] KVM: arm64: nv: Move last_vcpu_ran to be per s2 mmu Marc Zyngier
2019-07-01  9:10   ` Julien Thierry
2019-07-05 15:28   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 40/59] KVM: arm64: nv: Don't always start an S2 MMU search from the beginning Marc Zyngier
2019-07-09  9:59   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 41/59] KVM: arm64: nv: Introduce sys_reg_desc.forward_trap Marc Zyngier
2019-06-21  9:38 ` [PATCH 42/59] KVM: arm64: nv: Rework the system instruction emulation framework Marc Zyngier
2019-06-21  9:38 ` [PATCH 43/59] KVM: arm64: nv: Trap and emulate AT instructions from virtual EL2 Marc Zyngier
2019-07-01 15:45   ` Julien Thierry
2019-07-09 13:20   ` Alexandru Elisei
2019-07-18 12:13     ` Tomasz Nowicki
2019-07-18 12:36       ` Alexandru Elisei
2019-07-18 12:56         ` Alexandru Elisei
2019-07-18 12:59         ` Tomasz Nowicki
2019-07-24 10:25   ` Tomasz Nowicki
2019-07-24 12:39     ` Marc Zyngier
2019-07-24 13:56       ` Tomasz Nowicki
2019-06-21  9:38 ` [PATCH 44/59] KVM: arm64: nv: Trap and emulate TLBI " Marc Zyngier
2019-07-02 12:37   ` Julien Thierry
2019-07-10 10:15   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 45/59] KVM: arm64: nv: Handle traps for timer _EL02 and _EL2 sysregs accessors Marc Zyngier
2019-06-21  9:38 ` [PATCH 46/59] KVM: arm64: nv: arch_timer: Support hyp timer emulation Marc Zyngier
2019-07-10 16:23   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 47/59] KVM: arm64: nv: Propagate CNTVOFF_EL2 to the virtual EL1 timer Marc Zyngier
2019-08-08  9:34   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 48/59] KVM: arm64: nv: Load timer before the GIC Marc Zyngier
2019-07-11 13:17   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 49/59] KVM: arm64: nv: vgic-v3: Take cpu_if pointer directly instead of vcpu Marc Zyngier
2019-06-21  9:38 ` [PATCH 50/59] KVM: arm64: nv: Nested GICv3 Support Marc Zyngier
2019-07-16 11:41   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 51/59] KVM: arm64: nv: vgic: Emulate the HW bit in software Marc Zyngier
2019-06-21  9:38 ` [PATCH 52/59] KVM: arm64: nv: vgic: Allow userland to set VGIC maintenance IRQ Marc Zyngier
2019-07-04  7:38   ` Julien Thierry
2019-07-04  9:01     ` Andre Przywara
2019-07-04  9:04       ` Julien Thierry
2019-06-21  9:38 ` [PATCH 53/59] KVM: arm64: nv: Implement maintenance interrupt forwarding Marc Zyngier
2019-07-04  8:06   ` Julien Thierry
2019-07-16 16:35   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 54/59] KVM: arm64: nv: Add nested GICv3 tracepoints Marc Zyngier
2019-06-21  9:38 ` [PATCH 55/59] arm64: KVM: nv: Add handling of EL2-specific timer registers Marc Zyngier
2019-07-11 12:35   ` Alexandru Elisei
2019-07-17 10:19   ` Alexandru Elisei
2019-06-21  9:38 ` [PATCH 56/59] arm64: KVM: nv: Honor SCTLR_EL2.SPAN on entering vEL2 Marc Zyngier
2019-06-21  9:38 ` [PATCH 57/59] arm64: KVM: nv: Handle SCTLR_EL2 RES0/RES1 bits Marc Zyngier
2019-06-21  9:38 ` [PATCH 58/59] arm64: KVM: nv: Restrict S2 RD/WR permissions to match the guest's Marc Zyngier
2019-06-21  9:38 ` [PATCH 59/59] arm64: KVM: nv: Allow userspace to request KVM_ARM_VCPU_NESTED_VIRT Marc Zyngier
2019-06-21  9:57 ` [PATCH 00/59] KVM: arm64: ARMv8.3 Nested Virtualization support Itaru Kitayama
2019-06-21 11:21   ` Marc Zyngier
2019-08-02 10:11 ` Alexandru Elisei
2019-08-02 10:30   ` Andrew Jones
2019-08-09 10:01   ` Alexandru Elisei
2019-08-09 11:44     ` Andrew Jones
2019-08-09 12:00       ` Alexandru Elisei
2019-08-09 13:00         ` Andrew Jones
2019-08-22 11:57     ` Alexandru Elisei
2019-08-22 15:32       ` Alexandru Elisei

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