Re: [PATCH 1/3] KVM: arm64: Stash OSLSR_EL1 in the cpu context

From: Marc Zyngier <maz@kernel.org>
To: Oliver Upton <oupton@google.com>
Cc: kvm@vger.kernel.org, Peter Shier <pshier@google.com>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/3] KVM: arm64: Stash OSLSR_EL1 in the cpu context
Date: Fri, 29 Oct 2021 12:27:37 +0100	[thread overview]
Message-ID: <87lf2c9il2.wl-maz@kernel.org> (raw)
In-Reply-To: <20211029003202.158161-2-oupton@google.com>

On Fri, 29 Oct 2021 01:32:00 +0100,
Oliver Upton <oupton@google.com> wrote:
> 
> An upcoming change to KVM will context switch the OS Lock status between
> guest/host. Add OSLSR_EL1 to the cpu context and handle guest reads
> using the stored value.
> 
> Signed-off-by: Oliver Upton <oupton@google.com>
> ---
>  arch/arm64/include/asm/kvm_host.h |  1 +
>  arch/arm64/kvm/sys_regs.c         | 13 ++++++-------
>  2 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index f8be56d5342b..c98f65c4a1f7 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -172,6 +172,7 @@ enum vcpu_sysreg {
>  	MDSCR_EL1,	/* Monitor Debug System Control Register */
>  	MDCCINT_EL1,	/* Monitor Debug Comms Channel Interrupt Enable Reg */
>  	DISR_EL1,	/* Deferred Interrupt Status Register */
> +	OSLSR_EL1,	/* OS Lock Status Register */

Please move it one line up, next to the rest of the debug stuff
(DISR_EL1 is RAS and not debug).

>
>  	/* Performance Monitors Registers */
>  	PMCR_EL0,	/* Control Register */
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 1d46e185f31e..0eb03e7508fe 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -291,12 +291,11 @@ static bool trap_oslsr_el1(struct kvm_vcpu *vcpu,
>  			   struct sys_reg_params *p,
>  			   const struct sys_reg_desc *r)
>  {
> -	if (p->is_write) {
> +	if (p->is_write)
>  		return ignore_write(vcpu, p);

This should be UNDEF (though the HW should catch that, really).

> -	} else {
> -		p->regval = (1 << 3);
> -		return true;
> -	}
> +
> +	p->regval = vcpu_read_sys_reg(vcpu, r->reg);
> +	return true;
>  }
>  
>  static bool trap_dbgauthstatus_el1(struct kvm_vcpu *vcpu,
> @@ -1441,7 +1440,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  
>  	{ SYS_DESC(SYS_MDRAR_EL1), trap_raz_wi },
>  	{ SYS_DESC(SYS_OSLAR_EL1), trap_raz_wi },
> -	{ SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1 },
> +	{ SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1, reset_val, OSLSR_EL1, 0x00000008 },
>  	{ SYS_DESC(SYS_OSDLR_EL1), trap_raz_wi },
>  	{ SYS_DESC(SYS_DBGPRCR_EL1), trap_raz_wi },
>  	{ SYS_DESC(SYS_DBGCLAIMSET_EL1), trap_raz_wi },
> @@ -1916,7 +1915,7 @@ static const struct sys_reg_desc cp14_regs[] = {
>  	{ Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_raz_wi },
>  	DBGBXVR(1),
>  	/* DBGOSLSR */
> -	{ Op1( 0), CRn( 1), CRm( 1), Op2( 4), trap_oslsr_el1 },
> +	{ Op1( 0), CRn( 1), CRm( 1), Op2( 4), trap_oslsr_el1, NULL, OSLSR_EL1 },
>  	DBGBXVR(2),
>  	DBGBXVR(3),
>  	/* DBGOSDLR */

Please update tools/testing/selftests/kvm/aarch64/get-reg-list.c
before Andrew catches you red-handed! :D

	M.

-- 
Without deviation from the norm, progress is not possible.
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