Re: [PATCH v10 09/18] KVM: arm64: Repurpose vcpu_arch.debug_flags for general-purpose flags

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Dave Martin <Dave.Martin@xxxxxxx> writes:

> In struct vcpu_arch, the debug_flags field is used to store
> debug-related flags about the vcpu state.
>
> Since we are about to add some more flags related to FPSIMD and
> SVE, it makes sense to add them to the existing flags field rather
> than adding new fields.  Since there is only one debug_flags flag
> defined so far, there is plenty of free space for expansion.
>
> In preparation for adding more flags, this patch renames the
> debug_flags field to simply "flags", and updates comments
> appropriately.
>
> The flag definitions are also moved to <asm/kvm_host.h>, since
> their presence in <asm/kvm_asm.h> was for purely historical
> reasons:  these definitions are not used from asm any more, and not
> very likely to be as more Hyp asm is migrated to C.
>
> KVM_ARM64_DEBUG_DIRTY_SHIFT has not been used since commit
> 1ea66d27e7b0 ("arm64: KVM: Move away from the assembly version of
> the world switch"), so this patch gets rid of that too.
>
> No functional change.
>
> Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx>
> Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> Acked-by: Christoffer Dall <christoffer.dall@xxxxxxx>

Reviewed-by: Alex Bennée <alex.bennee@xxxxxxxxxx>

> ---
>  arch/arm64/include/asm/kvm_asm.h  | 3 ---
>  arch/arm64/include/asm/kvm_host.h | 7 +++++--
>  arch/arm64/kvm/debug.c            | 8 ++++----
>  arch/arm64/kvm/hyp/debug-sr.c     | 6 +++---
>  arch/arm64/kvm/hyp/sysreg-sr.c    | 4 ++--
>  arch/arm64/kvm/sys_regs.c         | 9 ++++-----
>  6 files changed, 18 insertions(+), 19 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index f6648a3..f62ccbf 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -30,9 +30,6 @@
>  /* The hyp-stub will return this for any kvm_call_hyp() call */
>  #define ARM_EXCEPTION_HYP_GONE	  HVC_STUB_ERR
>
> -#define KVM_ARM64_DEBUG_DIRTY_SHIFT	0
> -#define KVM_ARM64_DEBUG_DIRTY		(1 << KVM_ARM64_DEBUG_DIRTY_SHIFT)
> -
>  /* Translate a kernel address of @sym into its equivalent linear mapping */
>  #define kvm_ksym_ref(sym)						\
>  	({								\
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 469de8a..146c167 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -216,8 +216,8 @@ struct kvm_vcpu_arch {
>  	/* Exception Information */
>  	struct kvm_vcpu_fault_info fault;
>
> -	/* Guest debug state */
> -	u64 debug_flags;
> +	/* Miscellaneous vcpu state flags */
> +	u64 flags;
>
>  	/*
>  	 * We maintain more than a single set of debug registers to support
> @@ -293,6 +293,9 @@ struct kvm_vcpu_arch {
>  	bool sysregs_loaded_on_cpu;
>  };
>
> +/* vcpu_arch flags field values: */
> +#define KVM_ARM64_DEBUG_DIRTY		(1 << 0)
> +
>  #define vcpu_gp_regs(v)		(&(v)->arch.ctxt.gp_regs)
>
>  /*
> diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
> index a1f4ebd..00d4223 100644
> --- a/arch/arm64/kvm/debug.c
> +++ b/arch/arm64/kvm/debug.c
> @@ -103,7 +103,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
>   *
>   * Additionally, KVM only traps guest accesses to the debug registers if
>   * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
> - * flag on vcpu->arch.debug_flags).  Since the guest must not interfere
> + * flag on vcpu->arch.flags).  Since the guest must not interfere
>   * with the hardware state when debugging the guest, we must ensure that
>   * trapping is enabled whenever we are debugging the guest using the
>   * debug registers.
> @@ -111,7 +111,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
>
>  void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
>  {
> -	bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
> +	bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY);
>  	unsigned long mdscr;
>
>  	trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
> @@ -184,7 +184,7 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
>  			vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
>
>  			vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
> -			vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
> +			vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
>  			trap_debug = true;
>
>  			trace_kvm_arm_set_regset("BKPTS", get_num_brps(),
> @@ -206,7 +206,7 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
>
>  	/* 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.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
> +		vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
>
>  	trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
>  	trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
> diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c
> index 3e717f6..5000976 100644
> --- a/arch/arm64/kvm/hyp/debug-sr.c
> +++ b/arch/arm64/kvm/hyp/debug-sr.c
> @@ -163,7 +163,7 @@ void __hyp_text __debug_switch_to_guest(struct kvm_vcpu *vcpu)
>  	if (!has_vhe())
>  		__debug_save_spe_nvhe(&vcpu->arch.host_debug_state.pmscr_el1);
>
> -	if (!(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY))
> +	if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY))
>  		return;
>
>  	host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> @@ -185,7 +185,7 @@ void __hyp_text __debug_switch_to_host(struct kvm_vcpu *vcpu)
>  	if (!has_vhe())
>  		__debug_restore_spe_nvhe(vcpu->arch.host_debug_state.pmscr_el1);
>
> -	if (!(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY))
> +	if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY))
>  		return;
>
>  	host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> @@ -196,7 +196,7 @@ void __hyp_text __debug_switch_to_host(struct kvm_vcpu *vcpu)
>  	__debug_save_state(vcpu, guest_dbg, guest_ctxt);
>  	__debug_restore_state(vcpu, host_dbg, host_ctxt);
>
> -	vcpu->arch.debug_flags &= ~KVM_ARM64_DEBUG_DIRTY;
> +	vcpu->arch.flags &= ~KVM_ARM64_DEBUG_DIRTY;
>  }
>
>  u32 __hyp_text __kvm_get_mdcr_el2(void)
> diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index b3894df..35bc168 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -196,7 +196,7 @@ void __hyp_text __sysreg32_save_state(struct kvm_vcpu *vcpu)
>  	sysreg[DACR32_EL2] = read_sysreg(dacr32_el2);
>  	sysreg[IFSR32_EL2] = read_sysreg(ifsr32_el2);
>
> -	if (has_vhe() || vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY)
> +	if (has_vhe() || vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)
>  		sysreg[DBGVCR32_EL2] = read_sysreg(dbgvcr32_el2);
>  }
>
> @@ -218,7 +218,7 @@ void __hyp_text __sysreg32_restore_state(struct kvm_vcpu *vcpu)
>  	write_sysreg(sysreg[DACR32_EL2], dacr32_el2);
>  	write_sysreg(sysreg[IFSR32_EL2], ifsr32_el2);
>
> -	if (has_vhe() || vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY)
> +	if (has_vhe() || vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)
>  		write_sysreg(sysreg[DBGVCR32_EL2], dbgvcr32_el2);
>  }
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 6e3b969..a436373 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -31,7 +31,6 @@
>  #include <asm/debug-monitors.h>
>  #include <asm/esr.h>
>  #include <asm/kvm_arm.h>
> -#include <asm/kvm_asm.h>
>  #include <asm/kvm_coproc.h>
>  #include <asm/kvm_emulate.h>
>  #include <asm/kvm_host.h>
> @@ -338,7 +337,7 @@ static bool trap_debug_regs(struct kvm_vcpu *vcpu,
>  {
>  	if (p->is_write) {
>  		vcpu_write_sys_reg(vcpu, p->regval, r->reg);
> -		vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
> +		vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
>  	} else {
>  		p->regval = vcpu_read_sys_reg(vcpu, r->reg);
>  	}
> @@ -369,7 +368,7 @@ static void reg_to_dbg(struct kvm_vcpu *vcpu,
>  	}
>
>  	*dbg_reg = val;
> -	vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
> +	vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
>  }
>
>  static void dbg_to_reg(struct kvm_vcpu *vcpu,
> @@ -1441,7 +1440,7 @@ static bool trap_debug32(struct kvm_vcpu *vcpu,
>  {
>  	if (p->is_write) {
>  		vcpu_cp14(vcpu, r->reg) = p->regval;
> -		vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
> +		vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
>  	} else {
>  		p->regval = vcpu_cp14(vcpu, r->reg);
>  	}
> @@ -1473,7 +1472,7 @@ static bool trap_xvr(struct kvm_vcpu *vcpu,
>  		val |= p->regval << 32;
>  		*dbg_reg = val;
>
> -		vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
> +		vcpu->arch.flags |= KVM_ARM64_DEBUG_DIRTY;
>  	} else {
>  		p->regval = *dbg_reg >> 32;
>  	}


--
Alex Bennée
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