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Message-ID: <20190221115745.GB33673@lakrids.cambridge.arm.com>
Date: Thu, 21 Feb 2019 11:57:45 +0000
From: Mark Rutland <mark.rutland@....com>
To: Amit Daniel Kachhap <amit.kachhap@....com>
Cc: linux-arm-kernel@...ts.infradead.org,
Christoffer Dall <christoffer.dall@....com>,
Marc Zyngier <marc.zyngier@....com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Andrew Jones <drjones@...hat.com>,
Dave Martin <Dave.Martin@....com>,
Ramana Radhakrishnan <ramana.radhakrishnan@....com>,
kvmarm@...ts.cs.columbia.edu,
Kristina Martsenko <kristina.martsenko@....com>,
linux-kernel@...r.kernel.org, James Morse <james.morse@....com>,
Julien Thierry <julien.thierry@....com>
Subject: Re: [PATCH v6 2/6] arm64/kvm: preserve host MDCR_EL2 value
On Tue, Feb 19, 2019 at 02:54:27PM +0530, Amit Daniel Kachhap wrote:
> Save host MDCR_EL2 value during kvm HYP initialisation and restore
> after every switch from host to guest. There should not be any
> change in functionality due to this.
>
> The value of mdcr_el2 is now stored in struct kvm_cpu_context as
> both host and guest can now use this field in a common way.
>
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Christoffer Dall <christoffer.dall@....com>
> Cc: kvmarm@...ts.cs.columbia.edu
> ---
> arch/arm/include/asm/kvm_host.h | 1 -
> arch/arm64/include/asm/kvm_host.h | 6 ++----
> arch/arm64/kvm/debug.c | 28 ++++++----------------------
> arch/arm64/kvm/hyp/switch.c | 17 ++++-------------
> arch/arm64/kvm/hyp/sysreg-sr.c | 6 ++++++
> virt/kvm/arm/arm.c | 1 -
> 6 files changed, 18 insertions(+), 41 deletions(-)
This looks like a nice cleanup! FWIW:
Acked-by: Mark Rutland <mark.rutland@....com>
Thanks,
Mark.
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 05706b4..704667e 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -294,7 +294,6 @@ static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
> static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
>
> -static inline void kvm_arm_init_debug(void) {}
> static inline void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) {}
> static inline void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) {}
> static inline void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) {}
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1b2e05b..2f1bb86 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -205,6 +205,8 @@ struct kvm_cpu_context {
>
> /* HYP host/guest configuration */
> u64 hcr_el2;
> + u32 mdcr_el2;
> +
> struct kvm_vcpu *__hyp_running_vcpu;
> };
>
> @@ -213,9 +215,6 @@ typedef struct kvm_cpu_context kvm_cpu_context_t;
> struct kvm_vcpu_arch {
> struct kvm_cpu_context ctxt;
>
> - /* HYP configuration */
> - u32 mdcr_el2;
> -
> /* Exception Information */
> struct kvm_vcpu_fault_info fault;
>
> @@ -446,7 +445,6 @@ static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
> static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
> static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
>
> -void kvm_arm_init_debug(void);
> void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
> void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
> void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu);
> diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
> index f39801e..99dc0a4 100644
> --- a/arch/arm64/kvm/debug.c
> +++ b/arch/arm64/kvm/debug.c
> @@ -32,8 +32,6 @@
> DBG_MDSCR_KDE | \
> DBG_MDSCR_MDE)
>
> -static DEFINE_PER_CPU(u32, mdcr_el2);
> -
> /**
> * save/restore_guest_debug_regs
> *
> @@ -65,21 +63,6 @@ static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
> }
>
> /**
> - * kvm_arm_init_debug - grab what we need for debug
> - *
> - * Currently the sole task of this function is to retrieve the initial
> - * value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has
> - * presumably been set-up by some knowledgeable bootcode.
> - *
> - * It is called once per-cpu during CPU hyp initialisation.
> - */
> -
> -void kvm_arm_init_debug(void)
> -{
> - __this_cpu_write(mdcr_el2, kvm_call_hyp(__kvm_get_mdcr_el2));
> -}
> -
> -/**
> * kvm_arm_reset_debug_ptr - reset the debug ptr to point to the vcpu state
> */
>
> @@ -111,6 +94,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
>
> void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
> {
> + kvm_cpu_context_t *host_cxt = this_cpu_ptr(&kvm_host_cpu_state);
> bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY);
> unsigned long mdscr;
>
> @@ -120,8 +104,8 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
> * This also clears MDCR_EL2_E2PB_MASK to disable guest access
> * to the profiling buffer.
> */
> - vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
> - vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
> + vcpu->arch.ctxt.mdcr_el2 = host_cxt->mdcr_el2 & MDCR_EL2_HPMN_MASK;
> + vcpu->arch.ctxt.mdcr_el2 |= (MDCR_EL2_TPM |
> MDCR_EL2_TPMS |
> MDCR_EL2_TPMCR |
> MDCR_EL2_TDRA |
> @@ -130,7 +114,7 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
> /* Is Guest debugging in effect? */
> if (vcpu->guest_debug) {
> /* Route all software debug exceptions to EL2 */
> - vcpu->arch.mdcr_el2 |= MDCR_EL2_TDE;
> + vcpu->arch.ctxt.mdcr_el2 |= MDCR_EL2_TDE;
>
> /* Save guest debug state */
> save_guest_debug_regs(vcpu);
> @@ -202,13 +186,13 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
>
> /* Trap debug register access */
> if (trap_debug)
> - vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
> + vcpu->arch.ctxt.mdcr_el2 |= MDCR_EL2_TDA;
>
> /* If KDE or MDE are set, perform a full save/restore cycle. */
> if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE | DBG_MDSCR_MDE))
> vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
>
> - trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
> + trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.ctxt.mdcr_el2);
> trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
> }
>
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 006bd33..03b36f1 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -82,7 +82,7 @@ static void __hyp_text __activate_traps_common(struct kvm_vcpu *vcpu)
> */
> write_sysreg(0, pmselr_el0);
> write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
> - write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
> + write_sysreg(vcpu->arch.ctxt.mdcr_el2, mdcr_el2);
> }
>
> static void __hyp_text __deactivate_traps_common(void)
> @@ -157,14 +157,9 @@ static void deactivate_traps_vhe(struct kvm_cpu_context *host_ctxt)
>
> static void __hyp_text __deactivate_traps_nvhe(struct kvm_cpu_context *host_ctxt)
> {
> - u64 mdcr_el2 = read_sysreg(mdcr_el2);
> -
> __deactivate_traps_common();
>
> - mdcr_el2 &= MDCR_EL2_HPMN_MASK;
> - mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT;
> -
> - write_sysreg(mdcr_el2, mdcr_el2);
> + write_sysreg(host_ctxt->mdcr_el2, mdcr_el2);
> write_sysreg(host_ctxt->hcr_el2, hcr_el2);
> write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
> }
> @@ -196,13 +191,9 @@ void activate_traps_vhe_load(struct kvm_vcpu *vcpu)
>
> void deactivate_traps_vhe_put(struct kvm_vcpu *vcpu)
> {
> - u64 mdcr_el2 = read_sysreg(mdcr_el2);
> -
> - mdcr_el2 &= MDCR_EL2_HPMN_MASK |
> - MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT |
> - MDCR_EL2_TPMS;
> + struct kvm_cpu_context *host_ctxt = vcpu->arch.host_cpu_context;
>
> - write_sysreg(mdcr_el2, mdcr_el2);
> + write_sysreg(host_ctxt->mdcr_el2, mdcr_el2);
>
> __deactivate_traps_common();
> }
> diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index 68ddc0f..42ec50f 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -334,4 +334,10 @@ void __hyp_text __kvm_populate_host_regs(void)
> host_ctxt = __hyp_this_cpu_ptr(kvm_host_cpu_state);
>
> host_ctxt->hcr_el2 = read_sysreg(hcr_el2);
> + /*
> + * Retrieve the initial value of mdcr_el2 so we can preserve
> + * MDCR_EL2.HPMN which has presumably been set-up by some
> + * knowledgeable bootcode.
> + */
> + host_ctxt->mdcr_el2 = read_sysreg(mdcr_el2);
> }
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 8e18f7f..2032a66 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -1327,7 +1327,6 @@ static void cpu_hyp_reinit(void)
> else
> cpu_init_hyp_mode(NULL);
>
> - kvm_arm_init_debug();
> __cpu_copy_hyp_conf();
>
> if (vgic_present)
> --
> 2.7.4
>
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