From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marc Zyngier <marc.zyngier@arm.com>
Subject: Re: [PATCH v6 13/15] KVM: ARM: Handle I/O aborts
Date: Thu, 17 Jan 2013 16:37:00 +0000
Message-ID: <50F828AC.2050307@arm.com>
References: <20130116175716.29147.15348.stgit@ubuntu> <20130116175911.29147.40578.stgit@ubuntu>
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Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Will Deacon <Will.Deacon@arm.com>
To: Christoffer Dall <c.dall@virtualopensystems.com>
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On 16/01/13 17:59, Christoffer Dall wrote:
> When the guest accesses I/O memory this will create data abort
> exceptions and they are handled by decoding the HSR information
> (physical address, read/write, length, register) and forwarding reads
> and writes to QEMU which performs the device emulation.
> 
> Certain classes of load/store operations do not support the syndrome
> information provided in the HSR.  We don't support decoding these (patches
> are available elsewhere), so we report an error to user space in this case.
> 
> This requires changing the general flow somewhat since new calls to run
> the VCPU must check if there's a pending MMIO load and perform the write
> after userspace has made the data available.
> 
> Reviewed-by: Will Deacon <will.deacon@arm.com>
> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>

[...]

> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> index 04a9705..702743e 100644
> --- a/arch/arm/kvm/interrupts.S
> +++ b/arch/arm/kvm/interrupts.S
> @@ -192,6 +192,44 @@ after_vfp_restore:
>         mov     r0, r1                  @ Return the return code
>         bx      lr                      @ return to IOCTL
> 
> +
> +/********************************************************************
> + * Translate VA to PA
> + *
> + * u64 __kvm_va_to_pa(struct kvm_vcpu *vcpu, u32 va, bool priv)
> + *
> + * Arguments:
> + *  r0: pointer to vcpu struct
> + *  r1: virtual address to map (rounded to page)
> + *  r2: 1 = P1 (read) mapping, 0 = P0 (read) mapping.
> + * Returns 64 bit PAR value.
> + */
> +ENTRY(__kvm_va_to_pa)
> +       push    {r4-r12}
> +
> +       @ Fold flag into r1, easier than using stack.
> +       cmp     r2, #0
> +       movne   r2, #1
> +       orr     r1, r1, r2
> +
> +       @ This swaps too many registers, but we're in the slow path anyway.
> +       read_cp15_state store_to_vcpu = 0
> +       write_cp15_state read_from_vcpu = 1
> +
> +       ands    r2, r1, #1
> +       bic     r1, r1, r2
> +       mcrne   p15, 0, r1, c7, c8, 0   @ VA to PA, ATS1CPR
> +       mcreq   p15, 0, r1, c7, c8, 2   @ VA to PA, ATS1CUR
> +       isb
> +
> +       @ Restore host state.
> +       read_cp15_state store_to_vcpu = 1
> +       write_cp15_state read_from_vcpu = 0
> +
> +       mrrc    p15, 0, r0, r1, c7      @ PAR
> +       pop     {r4-r12}
> +       bx      lr
> +

Do we still need this function? Now that the MMIO emulation is gone,
there should be no need to perform a manual translation.

I can't even find a caller for it either.

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