Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1754758AbbGCHPf (ORCPT <rfc822;w@1wt.eu>);
	Fri, 3 Jul 2015 03:15:35 -0400
Received: from mail-wg0-f45.google.com ([74.125.82.45]:35343 "EHLO
	mail-wg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754565AbbGCHO4 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Fri, 3 Jul 2015 03:14:56 -0400
References: <1435775343-20034-1-git-send-email-alex.bennee@linaro.org> <1435775343-20034-9-git-send-email-alex.bennee@linaro.org> <20150702183440.GK11332@cbox>
From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
To: Christoffer Dall <christoffer.dall@linaro.org>
Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        kvmarm@lists.cs.columbia.edu, marc.zyngier@arm.com,
        peter.maydell@linaro.org, agraf@suse.de, drjones@redhat.com,
        pbonzini@redhat.com, zhichao.huang@linaro.org, jan.kiszka@siemens.com,
        dahi@linux.vnet.ibm.com, r65777@freescale.com, bp@suse.de,
        Gleb Natapov <gleb@kernel.org>, Russell King <linux@arm.linux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Richard Weinberger <richard@nod.at>,
        Andre Przywara <andre.przywara@arm.com>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 08/11] KVM: arm64: introduce vcpu->arch.debug_ptr
In-reply-to: <20150702183440.GK11332@cbox>
Date: Fri, 03 Jul 2015 08:14:52 +0100
Message-ID: <87mvzdsoer.fsf@linaro.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 3897
Lines: 121


Christoffer Dall <christoffer.dall@linaro.org> writes:

> On Wed, Jul 01, 2015 at 07:29:00PM +0100, Alex Bennée wrote:
>> This introduces a level of indirection for the debug registers. Instead
>> of using the sys_regs[] directly we store registers in a structure in
>> the vcpu. The new kvm_arm_reset_debug_ptr() sets the debug ptr to the
>> guest context.
>> 
>> This also entails updating the sys_regs code to access this new
>> structure. New access function have been added for each set of debug
>> registers. The generic functions are still used for the few registers
>> stored in the main context.
>> 
>> New access function pointers have been added to the sys_reg_desc
>> structure to support the GET/SET_ONE_REG ioctl operations.
>
> Why is this needed?

Previously I had a hacky:

	if (r->access == trap_debug64)
		return debug_get64(vcpu, r, reg, uaddr);

Which used the same offset information. Now we have a cleaner:

	if (r->set)
		return (r->set)(vcpu, r, reg, uaddr);

Which accesses the structure directly, as the trap functions do:

	__u64 *r = &vcpu->arch.vcpu_debug_state.dbg_bvr[rd->reg];
	if (copy_from_user(uaddr, r, KVM_REG_SIZE(reg->id)) != 0)
		return -EFAULT;
	return 0;

<snip>
>> +#if 0
>> +static int debug_set64(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
>> +		const struct kvm_one_reg *reg, void __user *uaddr)
>> +{
>> +	__u64 *r = (__u64 *) ((void * )&vcpu->arch.vcpu_debug_state + rd->reg);
>> +	if (copy_from_user(uaddr, r, KVM_REG_SIZE(reg->id)) != 0)
>> +		return -EFAULT;
>> +	return 0;
>> +}
>> +
>> +static int debug_get64(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
>> +	const struct kvm_one_reg *reg, void __user *uaddr)
>> +{
>> +	__u64 *r = (__u64 *) ((void * )&vcpu->arch.vcpu_debug_state + rd->reg);
>> +	if (copy_to_user(uaddr, r, KVM_REG_SIZE(reg->id)) != 0)
>> +		return -EFAULT;
>> +	return 0;
>> +}
>> +#endif
>> +
>
> what is this ifdef'ed block of code doing here?

Oops. Yeah looks like I missed removing that after I finished the
re-factor. These where the old get/set functions I used.

>
>>  int kvm_arm_sys_reg_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>>  {
>>  	const struct sys_reg_desc *r;
>> @@ -1303,6 +1530,9 @@ int kvm_arm_sys_reg_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg
>>  	if (!r)
>>  		return get_invariant_sys_reg(reg->id, uaddr);
>>  
>> +	if (r->get)
>> +		return (r->get)(vcpu, r, reg, uaddr);
>> +
>>  	return reg_to_user(uaddr, &vcpu_sys_reg(vcpu, r->reg), reg->id);
>>  }
>>  
>> @@ -1321,6 +1551,9 @@ int kvm_arm_sys_reg_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg
>>  	if (!r)
>>  		return set_invariant_sys_reg(reg->id, uaddr);
>>  
>> +	if (r->set)
>> +		return (r->set)(vcpu, r, reg, uaddr);
>> +
>>  	return reg_from_user(&vcpu_sys_reg(vcpu, r->reg), uaddr, reg->id);
>>  }
>>  
>> diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
>> index d411e25..9265e7d 100644
>> --- a/arch/arm64/kvm/sys_regs.h
>> +++ b/arch/arm64/kvm/sys_regs.h
>> @@ -55,6 +55,12 @@ struct sys_reg_desc {
>>  
>>  	/* Value (usually reset value) */
>>  	u64 val;
>> +
>> +	/* Get/Set functions, fallback if NULL */
>
> Is this only meant for usersapce access or when should one use these?

Yes for GET/SET

>
>> +	int (*get)(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
>> +		   const struct kvm_one_reg *reg, void __user *uaddr);
>> +	int (*set)(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
>> +		   const struct kvm_one_reg *reg, void __user *uaddr);
>>  };
>>  
>>  static inline void print_sys_reg_instr(const struct sys_reg_params *p)
>> -- 
>> 2.4.5
>> 

-- 
Alex Bennée
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/