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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 1/3] xen/arm: io: Distinguish unhandled IO from aborted one
On Thu, 1 Feb 2018, Julien Grall wrote:
> Currently, Xen is considering that an IO could either be handled or
> unhandled. When unhandled, the stage-2 abort function will try another
> way to resolve the abort.
>
> However, the MMIO emulation may return unhandled when the address
> belongs to an emulated range but was not correct. In that case, Xen
> should avoid to try another way and directly inject a guest data abort.
>
> Introduce a tri-state return to distinguish the following state:
> * IO_ABORT: The IO was handled but resulted in an abort
> * IO_HANDLED: The IO was handled
> * IO_UNHANDLED: The IO was unhandled
>
> For now, it is considered that an IO belonging to an emulated range
> could either be handled or inject an abort. This could be revisit in the
> future if overlapped region exist (or we want to try another way to
> resolve the abort).
>
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
>
> ---
> Changes in v2:
> - Always return IO_ABORT when the check failed because we know
> it was targeted emulated IO.
> - Fix typoes
> ---
> xen/arch/arm/io.c | 32 ++++++++++++++++++--------------
> xen/arch/arm/traps.c | 18 +++++++++++++++---
> xen/include/asm-arm/mmio.h | 13 ++++++++++---
> 3 files changed, 43 insertions(+), 20 deletions(-)
>
> diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
> index c3e9239ffe..1f4cb8f37d 100644
> --- a/xen/arch/arm/io.c
> +++ b/xen/arch/arm/io.c
> @@ -26,8 +26,9 @@
>
> #include "decode.h"
>
> -static int handle_read(const struct mmio_handler *handler, struct vcpu *v,
> - mmio_info_t *info)
> +static enum io_state handle_read(const struct mmio_handler *handler,
> + struct vcpu *v,
> + mmio_info_t *info)
> {
> const struct hsr_dabt dabt = info->dabt;
> struct cpu_user_regs *regs = guest_cpu_user_regs();
> @@ -40,7 +41,7 @@ static int handle_read(const struct mmio_handler *handler,
> struct vcpu *v,
> uint8_t size = (1 << dabt.size) * 8;
>
> if ( !handler->ops->read(v, info, &r, handler->priv) )
> - return 0;
> + return IO_ABORT;
>
> /*
> * Sign extend if required.
> @@ -60,17 +61,20 @@ static int handle_read(const struct mmio_handler
> *handler, struct vcpu *v,
>
> set_user_reg(regs, dabt.reg, r);
>
> - return 1;
> + return IO_HANDLED;
> }
>
> -static int handle_write(const struct mmio_handler *handler, struct vcpu *v,
> - mmio_info_t *info)
> +static enum io_state handle_write(const struct mmio_handler *handler,
> + struct vcpu *v,
> + mmio_info_t *info)
> {
> const struct hsr_dabt dabt = info->dabt;
> struct cpu_user_regs *regs = guest_cpu_user_regs();
> + int ret;
>
> - return handler->ops->write(v, info, get_user_reg(regs, dabt.reg),
> - handler->priv);
> + ret = handler->ops->write(v, info, get_user_reg(regs, dabt.reg),
> + handler->priv);
> + return ( ret ) ? IO_HANDLED : IO_ABORT;
> }
>
> /* This function assumes that mmio regions are not overlapped */
> @@ -103,9 +107,9 @@ static const struct mmio_handler
> *find_mmio_handler(struct domain *d,
> return handler;
> }
>
> -int try_handle_mmio(struct cpu_user_regs *regs,
> - const union hsr hsr,
> - paddr_t gpa)
> +enum io_state try_handle_mmio(struct cpu_user_regs *regs,
> + const union hsr hsr,
> + paddr_t gpa)
> {
> struct vcpu *v = current;
> const struct mmio_handler *handler = NULL;
> @@ -119,11 +123,11 @@ int try_handle_mmio(struct cpu_user_regs *regs,
>
> handler = find_mmio_handler(v->domain, info.gpa);
> if ( !handler )
> - return 0;
> + return IO_UNHANDLED;
Did you forget to send a patch? Or is there a prerequisite for this
series? This patch doesn't apply.
> /* All the instructions used on emulated MMIO region should be valid */
> if ( !dabt.valid )
> - return 0;
> + return IO_ABORT;
>
> /*
> * Erratum 766422: Thumb store translation fault to Hypervisor may
> @@ -138,7 +142,7 @@ int try_handle_mmio(struct cpu_user_regs *regs,
> if ( rc )
> {
> gprintk(XENLOG_DEBUG, "Unable to decode instruction\n");
> - return 0;
> + return IO_ABORT;
> }
> }
>
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 2f8d790bb3..1e85f99ec1 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -1964,10 +1964,21 @@ static void do_trap_stage2_abort_guest(struct
> cpu_user_regs *regs,
> *
> * Note that emulated region cannot be executed
> */
> - if ( is_data && try_handle_mmio(regs, hsr, gpa) )
> + if ( is_data )
> {
> - advance_pc(regs, hsr);
> - return;
> + enum io_state state = try_handle_mmio(regs, hsr, gpa);
> +
> + switch ( state )
> + {
> + case IO_ABORT:
> + goto inject_abt;
> + case IO_HANDLED:
> + advance_pc(regs, hsr);
> + return;
> + case IO_UNHANDLED:
> + /* IO unhandled, try another way to handle it. */
> + break;
> + }
> }
>
> /*
> @@ -1988,6 +1999,7 @@ static void do_trap_stage2_abort_guest(struct
> cpu_user_regs *regs,
> hsr.bits, xabt.fsc);
> }
>
> +inject_abt:
> gdprintk(XENLOG_DEBUG, "HSR=0x%x pc=%#"PRIregister" gva=%#"PRIvaddr
> " gpa=%#"PRIpaddr"\n", hsr.bits, regs->pc, gva, gpa);
> if ( is_data )
> diff --git a/xen/include/asm-arm/mmio.h b/xen/include/asm-arm/mmio.h
> index c941073257..c8dadb5006 100644
> --- a/xen/include/asm-arm/mmio.h
> +++ b/xen/include/asm-arm/mmio.h
> @@ -32,6 +32,13 @@ typedef struct
> paddr_t gpa;
> } mmio_info_t;
>
> +enum io_state
> +{
> + IO_ABORT, /* The IO was handled by the helper and led to an abort.
> */
> + IO_HANDLED, /* The IO was successfully handled by the helper. */
> + IO_UNHANDLED, /* The IO was not handled by the helper. */
> +};
> +
> typedef int (*mmio_read_t)(struct vcpu *v, mmio_info_t *info,
> register_t *r, void *priv);
> typedef int (*mmio_write_t)(struct vcpu *v, mmio_info_t *info,
> @@ -56,9 +63,9 @@ struct vmmio {
> struct mmio_handler *handlers;
> };
>
> -int try_handle_mmio(struct cpu_user_regs *regs,
> - const union hsr hsr,
> - paddr_t gpa);
> +enum io_state try_handle_mmio(struct cpu_user_regs *regs,
> + const union hsr hsr,
> + paddr_t gpa);
> void register_mmio_handler(struct domain *d,
> const struct mmio_handler_ops *ops,
> paddr_t addr, paddr_t size, void *priv);
> --
> 2.11.0
>
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