Re: [PATCH 2/7] arm64: Convert hcalls to use ISS field

From: Geoff Levand <geoff@infradead.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <Marc.Zyngier@arm.com>,
	Catalin Marinas <Catalin.Marinas@arm.com>,
	Will Deacon <Will.Deacon@arm.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"christoffer.dall@linaro.org" <christoffer.dall@linaro.org>
Subject: Re: [PATCH 2/7] arm64: Convert hcalls to use ISS field
Date: Fri, 03 Oct 2014 14:56:27 -0700	[thread overview]
Message-ID: <1412373387.32313.41.camel@smoke> (raw)
In-Reply-To: <20141003105106.GB26643@leverpostej>

Hi Mark,

On Fri, 2014-10-03 at 11:51 +0100, Mark Rutland wrote:
> On Thu, Sep 25, 2014 at 01:23:26AM +0100, Geoff Levand wrote:

>  index 7a5df52..99c319c 100644
> > --- a/arch/arm64/include/asm/virt.h
> > +++ b/arch/arm64/include/asm/virt.h
> > @@ -21,6 +21,26 @@
> >  #define BOOT_CPU_MODE_EL1	(0xe11)
> >  #define BOOT_CPU_MODE_EL2	(0xe12)
> >  
> > +/*
> > + * HVC_GET_VECTORS - Return the value of the vbar_el2 register.
> > + */
> > +
> > +#define HVC_GET_VECTORS 1
> > +
> > +/*
> > + * HVC_SET_VECTORS - Set the value of the vbar_el2 register.
> > + *
> > + * @x0: Physical address of the new vector table.
> > + */
> > +
> > +#define HVC_SET_VECTORS 2
> > +
> > +/*
> > + * HVC_CALL_HYP - Execute a hyp routine.
> > + */
> > +
> > +#define HVC_CALL_HYP 3
> > +
> >  #ifndef __ASSEMBLY__
> >  
> >  /*
> > diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
> > index a272f33..8b39522 100644
> > --- a/arch/arm64/kernel/hyp-stub.S
> > +++ b/arch/arm64/kernel/hyp-stub.S
> > @@ -53,14 +53,22 @@ ENDPROC(__hyp_stub_vectors)
> >  	.align 11
> >  
> >  el1_sync:
> > -	mrs	x1, esr_el2
> > -	lsr	x1, x1, #26
> > -	cmp	x1, #0x16
> > -	b.ne	2f				// Not an HVC trap
> > -	cbz	x0, 1f
> > -	msr	vbar_el2, x0			// Set vbar_el2
> > +	mrs	x18, esr_el2
> > +	lsr	x17, x18, #26			// x17=EC
> 
> The first patch enabled kvm_arm.h macros to be used from asm. Can't we
> use them here? If we don't include kvm_arm.h in the hyp stub, maybe we
> should (ideally we'd factor common stuff out, but I can see that getting
> messy fast).

I didn't want to tackle the cleanup of the headers in this patch
series, and I thought it odd to include a kvm header in this core
arm64 file, but maybe it is better to include kvm_arm.h and use the
ESR_EL2_ macros so the values are at least easier to understand and
keep track of.

> Assuming we can use them:
> 
> 	lsr	x17, x18, #ESR_EL2_EC_SHIFT
> 
> > +	and	x18, x18, #0xffffff		// x18=ISS
> 
> 	and	x18, x18, ESR_EL2_ISS
> 
> > +
> > +	cmp     x17, #0x16
> 
> 	cmp 	x17, #ESR_EL2_EC_HVC64
> 
> > +	b.ne    2f				// Not an HVC trap
> > +
> > +	cmp	x18, #HVC_GET_VECTORS
> > +	b.ne	1f
> > +	mrs	x0, vbar_el2
> >  	b	2f
> > -1:	mrs	x0, vbar_el2			// Return vbar_el2
> > +
> > +1:	cmp	x18, #HVC_SET_VECTORS
> > +	b.ne	2f
> > +	msr	vbar_el2, x0
> > +
> >  2:	eret
> >  ENDPROC(el1_sync)
> >  
> > @@ -100,11 +108,12 @@ ENDPROC(\label)
> >   * initialisation entry point.
> >   */
> >  
> > -ENTRY(__hyp_get_vectors)
> > -	mov	x0, xzr
> > -	// fall through
> >  ENTRY(__hyp_set_vectors)
> > -	hvc	#0
> > +	hvc	#HVC_SET_VECTORS
> >  	ret
> > -ENDPROC(__hyp_get_vectors)
> >  ENDPROC(__hyp_set_vectors)
> > +
> > +ENTRY(__hyp_get_vectors)
> > +	hvc	#HVC_GET_VECTORS
> > +	ret
> > +ENDPROC(__hyp_get_vectors)
> > diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> > index b72aa9f..9607f15 100644
> > --- a/arch/arm64/kvm/hyp.S
> > +++ b/arch/arm64/kvm/hyp.S
> > @@ -26,6 +26,7 @@
> >  #include <asm/kvm_asm.h>
> >  #include <asm/kvm_arm.h>
> >  #include <asm/kvm_mmu.h>
> > +#include <asm/virt.h>
> 
> As far as I can see, virt.h only defines BOOT_CPU_MODE_EL{1,2}, which we
> don't use below. So I don't think we need this include.

We need asm/virt.h for the new HVC_ macros added to it by this
patch (above)...

> Otherwise this looks fine to me.
> 
> Mark.
> 
> >  
> >  #define CPU_GP_REG_OFFSET(x)	(CPU_GP_REGS + x)
> >  #define CPU_XREG_OFFSET(x)	CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)
> > @@ -1105,12 +1106,9 @@ __hyp_panic_str:
> >   * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c).  Return values are
> >   * passed in r0 and r1.
> >   *
> > - * A function pointer with a value of 0 has a special meaning, and is
> > - * used to implement __hyp_get_vectors in the same way as in
> > - * arch/arm64/kernel/hyp_stub.S.
> >   */
> >  ENTRY(kvm_call_hyp)
> > -	hvc	#0
> > +	hvc	#HVC_CALL_HYP
> >  	ret
> >  ENDPROC(kvm_call_hyp)

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