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From: Mark Rutland <mark.rutland@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>,
	kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	qperret@google.com, kernel-team@android.com
Subject: Re: [PATCH 3/4] KVM: arm64: Rename SCTLR_ELx_FLAGS to SCTLR_EL2_FLAGS
Date: Thu, 11 Mar 2021 11:35:29 +0000	[thread overview]
Message-ID: <20210311113529.GD37303@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20210310182022.GA29969@willie-the-truck>

On Wed, Mar 10, 2021 at 06:20:22PM +0000, Will Deacon wrote:
> On Wed, Mar 10, 2021 at 05:49:17PM +0000, Marc Zyngier wrote:
> > On Wed, 10 Mar 2021 16:15:47 +0000,
> > Will Deacon <will@kernel.org> wrote:
> > > On Wed, Mar 10, 2021 at 04:05:17PM +0000, Marc Zyngier wrote:
> > > > On Wed, 10 Mar 2021 15:46:26 +0000,
> > > > Will Deacon <will@kernel.org> wrote:
> > > > > On Wed, Mar 10, 2021 at 03:26:55PM +0000, Marc Zyngier wrote:
> > > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> > > > > > index 4eb584ae13d9..7423f4d961a4 100644
> > > > > > --- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> > > > > > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> > > > > > @@ -122,7 +122,7 @@ alternative_else_nop_endif
> > > > > >  	 * as well as the EE bit on BE. Drop the A flag since the compiler
> > > > > >  	 * is allowed to generate unaligned accesses.
> > > > > >  	 */
> > > > > > -	mov_q	x0, (SCTLR_EL2_RES1 | (SCTLR_ELx_FLAGS & ~SCTLR_ELx_A))
> > > > > > +	mov_q	x0, (SCTLR_EL2_RES1 | (SCTLR_EL2_FLAGS & ~SCTLR_ELx_A))
> > > > > 
> > > > > Can we just drop SCTLR_ELx_A from SCTLR_EL2_FLAGS instead of clearing it
> > > > > here?
> > > > 
> > > > Absolutely. That'd actually be an improvement.
> > > 
> > > In fact, maybe just define INIT_SCTLR_EL2_MMU_ON to mirror what we do for
> > > EL1 (i.e. including the RES1 bits) and then use that here?
> > 
> > Like this?
> > 
> > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> > index dfd4edbfe360..593b9bf91bbd 100644
> > --- a/arch/arm64/include/asm/sysreg.h
> > +++ b/arch/arm64/include/asm/sysreg.h
> > @@ -579,9 +579,6 @@
> >  #define SCTLR_ELx_A	(BIT(1))
> >  #define SCTLR_ELx_M	(BIT(0))
> >  
> > -#define SCTLR_ELx_FLAGS	(SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C | \
> > -			 SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB)
> > -
> >  /* SCTLR_EL2 specific flags. */
> >  #define SCTLR_EL2_RES1	((BIT(4))  | (BIT(5))  | (BIT(11)) | (BIT(16)) | \
> >  			 (BIT(18)) | (BIT(22)) | (BIT(23)) | (BIT(28)) | \
> > @@ -593,6 +590,10 @@
> >  #define ENDIAN_SET_EL2		0
> >  #endif
> >  
> > +#define INIT_SCTLR_EL2_MMU_ON						\
> > +	(SCTLR_ELx_M  | SCTLR_ELx_C | SCTLR_ELx_SA | SCTLR_ELx_I |	\
> > +	 SCTLR_ELx_IESB | ENDIAN_SET_EL2 | SCTLR_EL2_RES1)
> > +
> >  #define INIT_SCTLR_EL2_MMU_OFF \
> >  	(SCTLR_EL2_RES1 | ENDIAN_SET_EL2)
> >  
> > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> > index 4eb584ae13d9..2e16b2098bbd 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
> > @@ -117,13 +117,7 @@ alternative_else_nop_endif
> >  	tlbi	alle2
> >  	dsb	sy
> >  
> > -	/*
> > -	 * Preserve all the RES1 bits while setting the default flags,
> > -	 * as well as the EE bit on BE. Drop the A flag since the compiler
> > -	 * is allowed to generate unaligned accesses.
> > -	 */
> > -	mov_q	x0, (SCTLR_EL2_RES1 | (SCTLR_ELx_FLAGS & ~SCTLR_ELx_A))
> > -CPU_BE(	orr	x0, x0, #SCTLR_ELx_EE)
> > +	mov_q	x0, INIT_SCTLR_EL2_MMU_ON
> >  alternative_if ARM64_HAS_ADDRESS_AUTH
> >  	mov_q	x1, (SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
> >  		     SCTLR_ELx_ENDA | SCTLR_ELx_ENDB)
> 
> Beautiful!
> 
> With that, you can have my ack on the whole series:
> 
> Acked-by: Will Deacon <will@kernel.org>

FWIW, likewise:

Acked-by: Mark Rutland <nark.rutland@arm.com>

This is really nice!

Thanks,
Mark.

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  reply	other threads:[~2021-03-11 11:37 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-10 15:26 [PATCH 0/4] KVM: arm64: Running the EL2 nVHE code with WXN Marc Zyngier
2021-03-10 15:26 ` [PATCH 1/4] arm64: Use INIT_SCTLR_EL1_MMU_OFF to disable the MMU on CPU restart Marc Zyngier
2021-03-10 15:26 ` [PATCH 2/4] KVM: arm64: Use INIT_SCTLR_EL2_MMU_OFF to disable the MMU on KVM teardown Marc Zyngier
2021-03-10 15:26 ` [PATCH 3/4] KVM: arm64: Rename SCTLR_ELx_FLAGS to SCTLR_EL2_FLAGS Marc Zyngier
2021-03-10 15:46   ` Will Deacon
2021-03-10 16:05     ` Marc Zyngier
2021-03-10 16:15       ` Will Deacon
2021-03-10 17:49         ` Marc Zyngier
2021-03-10 18:20           ` Will Deacon
2021-03-11 11:35             ` Mark Rutland [this message]
2021-03-11 12:00               ` Mark Rutland
2021-03-10 15:26 ` [PATCH 4/4] KVM: arm64: Force SCTLR_EL2.WXN when running nVHE Marc Zyngier

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