Re: [PATCH v6 13/15] KVM: ARM: Handle I/O aborts

Marc Zyngier
2013-01-17T16:37:03Z

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...