Re: [PATCH v2 08/21] arm64: KVM: Implement debug save/restore

[Marc Zyngier <marc.zyngier@arm.com>]

On Mon, 30 Nov 2015 12:00:24 +0000
Alex Bennée <alex.bennee@linaro.org> wrote:

> 
> Marc Zyngier <marc.zyngier@arm.com> writes:
> 
> > Implement the debug save restore as a direct translation of
> > the assembly code version.
> >
> > Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> > ---
> >  arch/arm64/kvm/hyp/Makefile   |   1 +
> >  arch/arm64/kvm/hyp/debug-sr.c | 130 ++++++++++++++++++++++++++++++++++++++++++
> >  arch/arm64/kvm/hyp/hyp.h      |   9 +++
> >  3 files changed, 140 insertions(+)
> >  create mode 100644 arch/arm64/kvm/hyp/debug-sr.c
> >
> > diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> > index ec94200..ec14cac 100644
> > --- a/arch/arm64/kvm/hyp/Makefile
> > +++ b/arch/arm64/kvm/hyp/Makefile
> > @@ -6,3 +6,4 @@ obj-$(CONFIG_KVM_ARM_HOST) += vgic-v2-sr.o
> >  obj-$(CONFIG_KVM_ARM_HOST) += vgic-v3-sr.o
> >  obj-$(CONFIG_KVM_ARM_HOST) += timer-sr.o
> >  obj-$(CONFIG_KVM_ARM_HOST) += sysreg-sr.o
> > +obj-$(CONFIG_KVM_ARM_HOST) += debug-sr.o
> > diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c
> > new file mode 100644
> > index 0000000..a0b2b99
> > --- /dev/null
> > +++ b/arch/arm64/kvm/hyp/debug-sr.c
> > @@ -0,0 +1,130 @@
> > +/*
> > + * Copyright (C) 2015 - ARM Ltd
> > + * Author: Marc Zyngier <marc.zyngier@arm.com>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> > + */
> > +
> > +#include <linux/compiler.h>
> > +#include <linux/kvm_host.h>
> > +
> > +#include <asm/kvm_mmu.h>
> > +
> > +#include "hyp.h"
> > +
> > +#define read_debug(r,n)		read_sysreg(r##n##_el1)
> > +#define write_debug(v,r,n)	write_sysreg(v, r##n##_el1)
> > +
> > +#define save_debug(ptr,reg,nr)						\
> > +	switch (nr) {							\
> > +	case 15:	ptr[15] = read_debug(reg, 15);			\
> > +	case 14:	ptr[14] = read_debug(reg, 14);			\
> > +	case 13:	ptr[13] = read_debug(reg, 13);			\
> > +	case 12:	ptr[12] = read_debug(reg, 12);			\
> > +	case 11:	ptr[11] = read_debug(reg, 11);			\
> > +	case 10:	ptr[10] = read_debug(reg, 10);			\
> > +	case 9:		ptr[9] = read_debug(reg, 9);			\
> > +	case 8:		ptr[8] = read_debug(reg, 8);			\
> > +	case 7:		ptr[7] = read_debug(reg, 7);			\
> > +	case 6:		ptr[6] = read_debug(reg, 6);			\
> > +	case 5:		ptr[5] = read_debug(reg, 5);			\
> > +	case 4:		ptr[4] = read_debug(reg, 4);			\
> > +	case 3:		ptr[3] = read_debug(reg, 3);			\
> > +	case 2:		ptr[2] = read_debug(reg, 2);			\
> > +	case 1:		ptr[1] = read_debug(reg, 1);			\
> > +	default:	ptr[0] = read_debug(reg, 0);			\
> > +	}
> > +
> > +#define restore_debug(ptr,reg,nr)					\
> > +	switch (nr) {							\
> > +	case 15:	write_debug(ptr[15], reg, 15);			\
> > +	case 14:	write_debug(ptr[14], reg, 14);			\
> > +	case 13:	write_debug(ptr[13], reg, 13);			\
> > +	case 12:	write_debug(ptr[12], reg, 12);			\
> > +	case 11:	write_debug(ptr[11], reg, 11);			\
> > +	case 10:	write_debug(ptr[10], reg, 10);			\
> > +	case 9:		write_debug(ptr[9], reg, 9);			\
> > +	case 8:		write_debug(ptr[8], reg, 8);			\
> > +	case 7:		write_debug(ptr[7], reg, 7);			\
> > +	case 6:		write_debug(ptr[6], reg, 6);			\
> > +	case 5:		write_debug(ptr[5], reg, 5);			\
> > +	case 4:		write_debug(ptr[4], reg, 4);			\
> > +	case 3:		write_debug(ptr[3], reg, 3);			\
> > +	case 2:		write_debug(ptr[2], reg, 2);			\
> > +	case 1:		write_debug(ptr[1], reg, 1);			\
> > +	default:	write_debug(ptr[0], reg, 0);			\
> > +	}
> > +
> > +void __hyp_text __debug_save_state(struct kvm_vcpu *vcpu,
> > +				   struct kvm_guest_debug_arch *dbg,
> > +				   struct kvm_cpu_context *ctxt)
> > +{
> > +	if (vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY) {
> > +		u64 aa64dfr0 = read_sysreg(id_aa64dfr0_el1);
> > +		int brps, wrps;
> > +
> > +		brps = (aa64dfr0 >> 12) & 0xf;
> > +		wrps = (aa64dfr0 >> 20) & 0xf;
> 
> I'm sure we have that defined - get_num_brps/wrps() - but I don't know
> if the compiler would do a better job with it.

The problem is that it lives in the main kernel text, which makes it
unavailable to the hyp code.

> > +
> > +		save_debug(dbg->dbg_bcr, dbgbcr, brps);
> > +		save_debug(dbg->dbg_bvr, dbgbvr, brps);
> > +		save_debug(dbg->dbg_wcr, dbgwcr, wrps);
> > +		save_debug(dbg->dbg_wvr, dbgwvr, wrps);
> > +
> > +		ctxt->sys_regs[MDCCINT_EL1] = read_sysreg(mdccint_el1);
> > +	}
> > +}
> > +
> > +void __hyp_text __debug_restore_state(struct kvm_vcpu *vcpu,
> > +				      struct kvm_guest_debug_arch *dbg,
> > +				      struct kvm_cpu_context *ctxt)
> > +{
> > +	if (vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY) {
> > +		u64 aa64dfr0 = read_sysreg(id_aa64dfr0_el1);
> > +		int brps, wrps;
> > +
> > +		brps = (aa64dfr0 >> 12) & 0xf;
> > +		wrps = (aa64dfr0 >> 20) & 0xf;
> > +
> > +		restore_debug(dbg->dbg_bcr, dbgbcr, brps);
> > +		restore_debug(dbg->dbg_bvr, dbgbvr, brps);
> > +		restore_debug(dbg->dbg_wcr, dbgwcr, wrps);
> > +		restore_debug(dbg->dbg_wvr, dbgwvr, wrps);
> > +
> > +		write_sysreg(ctxt->sys_regs[MDCCINT_EL1], mdccint_el1);
> > +	}
> > +}
> > +
> > +void __hyp_text __debug_cond_save_host_state(struct kvm_vcpu *vcpu)
> > +{
> > +	if ((vcpu->arch.ctxt.sys_regs[MDSCR_EL1] & DBG_MDSCR_KDE) ||
> > +	    (vcpu->arch.ctxt.sys_regs[MDSCR_EL1] & DBG_MDSCR_KDE))
> > +		vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
> > +
> > +	__debug_save_state(vcpu, &vcpu->arch.host_debug_state,
> > +			   kern_hyp_va(vcpu->arch.host_cpu_context));
> > +}
> > +
> > +void __hyp_text __debug_cond_restore_host_state(struct kvm_vcpu *vcpu)
> > +{
> > +	if (vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY) {
> > +		__debug_restore_state(vcpu, &vcpu->arch.host_debug_state,
> > +				      kern_hyp_va(vcpu->arch.host_cpu_context));
> > +		vcpu->arch.debug_flags &= ~KVM_ARM64_DEBUG_DIRTY;
> > +	}
> > +}
> > +
> > +u32 __hyp_text __debug_read_mdcr_el2(void)
> > +{
> > +	return read_sysreg(mdcr_el2);
> > +}
> > diff --git a/arch/arm64/kvm/hyp/hyp.h b/arch/arm64/kvm/hyp/hyp.h
> > index 4639330..2581232 100644
> > --- a/arch/arm64/kvm/hyp/hyp.h
> > +++ b/arch/arm64/kvm/hyp/hyp.h
> > @@ -41,5 +41,14 @@ void __sysreg_restore_state(struct kvm_cpu_context *ctxt);
> >  void __sysreg32_save_state(struct kvm_vcpu *vcpu);
> >  void __sysreg32_restore_state(struct kvm_vcpu *vcpu);
> >
> > +void __debug_save_state(struct kvm_vcpu *vcpu,
> > +			struct kvm_guest_debug_arch *dbg,
> > +			struct kvm_cpu_context *ctxt);
> > +void __debug_restore_state(struct kvm_vcpu *vcpu,
> > +			   struct kvm_guest_debug_arch *dbg,
> > +			   struct kvm_cpu_context *ctxt);
> > +void __debug_cond_save_host_state(struct kvm_vcpu *vcpu);
> > +void __debug_cond_restore_host_state(struct kvm_vcpu *vcpu);
> > +
> >  #endif /* __ARM64_KVM_HYP_H__ */
> 
> I spun it up against my KVM debug tests and everything was fine. Have a:
> 
> Tested-by: Alex Bennée <alex.bennee@linaro.org>
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

Awesome. Thanks Alex!

	M.
-- 
Jazz is not dead. It just smells funny.
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