RE: [PATCH 09/11] xen/arm: if 1:1 direct-map domain use native UART address and IRQ number for vPL011

[Penny Zheng <Penny.Zheng@xxxxxxx>]

Hi Julien

> -----Original Message-----
> From: Julien Grall <julien@xxxxxxx>
> Sent: Monday, October 11, 2021 6:49 PM
> To: Penny Zheng <Penny.Zheng@xxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx;
> sstabellini@xxxxxxxxxx
> Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>; Wei Chen
> <Wei.Chen@xxxxxxx>
> Subject: Re: [PATCH 09/11] xen/arm: if 1:1 direct-map domain use native UART
> address and IRQ number for vPL011
> 
> On 09/10/2021 09:47, Penny Zheng wrote:
> > Hi Julien
> 
> Hi Penny,
> 
> >> -----Original Message-----
> >> From: Julien Grall <julien@xxxxxxx>
> >> Sent: Thursday, September 23, 2021 7:14 PM
> >> To: Penny Zheng <Penny.Zheng@xxxxxxx>;
> >> xen-devel@xxxxxxxxxxxxxxxxxxxx; sstabellini@xxxxxxxxxx
> >> Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>; Wei Chen
> >> <Wei.Chen@xxxxxxx>
> >> Subject: Re: [PATCH 09/11] xen/arm: if 1:1 direct-map domain use
> >> native UART address and IRQ number for vPL011
> >>
> >>
> >>
> >> On 23/09/2021 08:11, Penny Zheng wrote:
> >>> From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> >>>
> >>> We always use a fix address to map the vPL011 to domains. The
> >>> address could be a problem for domains that are directly mapped.
> >>>
> >>> So, for domains that are directly mapped, reuse the address of the
> >>> physical UART on the platform to avoid potential clashes.
> >>>
> >>> Do the same for the virtual IRQ number: instead of always using
> >>> GUEST_VPL011_SPI, try to reuse the physical SPI number if possible.
> >>>
> >>> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> >>> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> >>> ---
> >>>    xen/arch/arm/domain_build.c  | 34 +++++++++++++++++++++++++++-----
> --
> >>>    xen/arch/arm/vpl011.c        | 34 +++++++++++++++++++++++++++-------
> >>>    xen/include/asm-arm/vpl011.h |  2 ++
> >>>    3 files changed, 56 insertions(+), 14 deletions(-)
> >>>
> >>> diff --git a/xen/arch/arm/domain_build.c
> >>> b/xen/arch/arm/domain_build.c index 120f1ae575..c92e510ae7 100644
> >>> --- a/xen/arch/arm/domain_build.c
> >>> +++ b/xen/arch/arm/domain_build.c
> >>> @@ -30,6 +30,7 @@
> >>>
> >>>    #include <xen/irq.h>
> >>>    #include <xen/grant_table.h>
> >>> +#include <xen/serial.h>
> >>>
> >>>    static unsigned int __initdata opt_dom0_max_vcpus;
> >>>    integer_param("dom0_max_vcpus", opt_dom0_max_vcpus); @@ -
> 1942,8
> >>> +1943,11 @@ static int __init make_vpl011_uart_node(struct
> >>> +kernel_info
> >> *kinfo)
> >>>        gic_interrupt_t intr;
> >>>        __be32 reg[GUEST_ROOT_ADDRESS_CELLS +
> GUEST_ROOT_SIZE_CELLS];
> >>>        __be32 *cells;
> >>> +    struct domain *d = kinfo->d;
> >>> +    char buf[27];
> >>>
> >>> -    res = fdt_begin_node(fdt, "sbsa-
> uart@"__stringify(GUEST_PL011_BASE));
> >>> +    snprintf(buf, sizeof(buf), "sbsa-uart@%"PRIx64, d-
> >>> arch.vpl011.base_addr);
> >>> +    res = fdt_begin_node(fdt, buf);
> >>>        if ( res )
> >>>            return res;
> >>>
> >>> @@ -1953,14 +1957,14 @@ static int __init
> >>> make_vpl011_uart_node(struct kernel_info *kinfo)
> >>>
> >>>        cells = &reg[0];
> >>>        dt_child_set_range(&cells, GUEST_ROOT_ADDRESS_CELLS,
> >>> -                       GUEST_ROOT_SIZE_CELLS, GUEST_PL011_BASE,
> >>> +                       GUEST_ROOT_SIZE_CELLS,
> >>> + d->arch.vpl011.base_addr,
> >>>                           GUEST_PL011_SIZE);
> >>>
> >>>        res = fdt_property(fdt, "reg", reg, sizeof(reg));
> >>>        if ( res )
> >>>            return res;
> >>>
> >>> -    set_interrupt(intr, GUEST_VPL011_SPI, 0xf, DT_IRQ_TYPE_LEVEL_HIGH);
> >>> +    set_interrupt(intr, d->arch.vpl011.virq, 0xf,
> >>> + DT_IRQ_TYPE_LEVEL_HIGH);
> >>>
> >>>        res = fdt_property(fdt, "interrupts", intr, sizeof (intr));
> >>>        if ( res )
> >>> @@ -2670,6 +2674,13 @@ static int __init construct_domU(struct
> >>> domain
> >> *d,
> >>>        else
> >>>            allocate_static_memory(d, &kinfo, node);
> >>>
> >>> +    /*
> >>> +     * Initialization before creating its device
> >>> +     * tree node in prepare_dtb_domU.
> >>> +     */
> >>
> >> I think it would be better to explain *why* this needs to be done before.
> >>
> >>> +    if ( kinfo.vpl011 )
> >>> +        rc = domain_vpl011_init(d, NULL);
> >>> +
> >>>        rc = prepare_dtb_domU(d, &kinfo);
> >>>        if ( rc < 0 )
> >>>            return rc;
> >>> @@ -2678,9 +2689,6 @@ static int __init construct_domU(struct domain
> >> *d,
> >>>        if ( rc < 0 )
> >>>            return rc;
> >>>
> >>> -    if ( kinfo.vpl011 )
> >>> -        rc = domain_vpl011_init(d, NULL);
> >>> -
> >>>        return rc;
> >>>    }
> >>>
> >>> @@ -2723,15 +2731,27 @@ void __init create_domUs(void)
> >>>
> >>>            if ( !dt_property_read_u32(node, "nr_spis", 
> >>> &d_cfg.arch.nr_spis) )
> >>>            {
> >>> +            unsigned int vpl011_virq = GUEST_VPL011_SPI;
> >>
> >> Coding style: Add a newline here.
> >>
> >>>                d_cfg.arch.nr_spis = gic_number_lines() - 32;
> >>>
> >>> +            /*
> >>> +             * The VPL011 virq is GUEST_VPL011_SPI, unless direct-map in
> >>> +             * set, in which case we'll try to match the hardware.
> >>> +             *
> >>> +             * Typically, d->arch.vpl011.virq has the vpl011 irq number
> >>> +             * but at this point of the boot sequence it is not
> >>> +             * initialized yet.
> >>> +             */
> >>> +            if ( direct_map && serial_irq(SERHND_DTUART) > 0 )
> >>> +                vpl011_virq = serial_irq(SERHND_DTUART);
> >>
> >> I think we should not continue if the domain is direct-mapped *and*
> >> the IRQ is not found. Otherwise, this will may just result to
> >> potential breakage if GUEST_VPL011_SPI happens to be used for an HW
> device.
> >>
> >>> +
> >>>                /*
> >>>                 * vpl011 uses one emulated SPI. If vpl011 is requested, 
> >>> make
> >>>                 * sure that we allocate enough SPIs for it.
> >>>                 */
> >>>                if ( dt_property_read_bool(node, "vpl011") )
> >>>                    d_cfg.arch.nr_spis = MAX(d_cfg.arch.nr_spis,
> >>> -                                         GUEST_VPL011_SPI - 32 + 1);
> >>> +                                         vpl011_virq - 32 + 1);
> >>>            }
> >>>
> >>>            /*
> >>> diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c index
> >>> 895f436cc4..10df25f098 100644
> >>> --- a/xen/arch/arm/vpl011.c
> >>> +++ b/xen/arch/arm/vpl011.c
> >>> @@ -29,6 +29,7 @@
> >>>    #include <xen/mm.h>
> >>>    #include <xen/sched.h>
> >>>    #include <xen/console.h>
> >>> +#include <xen/serial.h>
> >>>    #include <public/domctl.h>
> >>>    #include <public/io/console.h>
> >>>    #include <asm/pl011-uart.h>
> >>> @@ -71,11 +72,11 @@ static void
> >>> vpl011_update_interrupt_status(struct
> >> domain *d)
> >>>         * status bit has been set since the last time.
> >>>         */
> >>>        if ( uartmis & ~vpl011->shadow_uartmis )
> >>> -        vgic_inject_irq(d, NULL, GUEST_VPL011_SPI, true);
> >>> +        vgic_inject_irq(d, NULL, vpl011->virq, true);
> >>>
> >>>        vpl011->shadow_uartmis = uartmis;
> >>>    #else
> >>> -    vgic_inject_irq(d, NULL, GUEST_VPL011_SPI, uartmis);
> >>> +    vgic_inject_irq(d, NULL, vpl011->virq, uartmis);
> >>>    #endif
> >>>    }
> >>>
> >>> @@ -347,7 +348,8 @@ static int vpl011_mmio_read(struct vcpu *v,
> >>>                                void *priv)
> >>>    {
> >>>        struct hsr_dabt dabt = info->dabt;
> >>> -    uint32_t vpl011_reg = (uint32_t)(info->gpa - GUEST_PL011_BASE);
> >>> +    uint32_t vpl011_reg = (uint32_t)(info->gpa -
> >>> +
> >>> + v->domain->arch.vpl011.base_addr);
> >>>        struct vpl011 *vpl011 = &v->domain->arch.vpl011;
> >>>        struct domain *d = v->domain;
> >>>        unsigned long flags;
> >>> @@ -430,7 +432,8 @@ static int vpl011_mmio_write(struct vcpu *v,
> >>>                                 void *priv)
> >>>    {
> >>>        struct hsr_dabt dabt = info->dabt;
> >>> -    uint32_t vpl011_reg = (uint32_t)(info->gpa - GUEST_PL011_BASE);
> >>> +    uint32_t vpl011_reg = (uint32_t)(info->gpa -
> >>> +
> >>> + v->domain->arch.vpl011.base_addr);
> >>>        struct vpl011 *vpl011 = &v->domain->arch.vpl011;
> >>>        struct domain *d = v->domain;
> >>>        unsigned long flags;
> >>> @@ -622,10 +625,27 @@ int domain_vpl011_init(struct domain *d,
> >>> struct
> >> vpl011_init_info *info)
> >>>    {
> >>>        int rc;
> >>>        struct vpl011 *vpl011 = &d->arch.vpl011;
> >>> +    const struct vuart_info *uart =
> >>> + serial_vuart_info(SERHND_DTUART);
> >>>
> >>>        if ( vpl011->backend.dom.ring_buf )
> >>>            return -EINVAL;
> >>>
> >>> +    vpl011->base_addr = GUEST_PL011_BASE;
> >>> +    vpl011->virq = GUEST_VPL011_SPI;
> >>> +    if ( is_domain_direct_mapped(d) )
> >>> +    {
> >>> +        if ( uart != NULL && serial_irq(SERHND_DTUART) > 0 )
> >>> +        {
> >>> +            vpl011->base_addr = uart->base_addr;
> >>> +            vpl011->virq = serial_irq(SERHND_DTUART);
> >>
> >> This seems a bit pointless to call serial_irq() twice. How about add
> >> a field in vuart_info to return the interrupt number?
> >>
> >>> +        }
> >>> +        else
> >>> +            printk(XENLOG_ERR
> >>> +                   "Unable to reuse physical UART address and irq for 
> >>> vPL011.\n"
> >>> +                   "Defaulting to addr %#"PRIpaddr" and IRQ %u\n",
> >>> +                   vpl011->base_addr, vpl011->virq);
> >>> +    }
> >>> +
> >>>        /*
> >>>         * info is NULL when the backend is in Xen.
> >>>         * info is != NULL when the backend is in a domain.
> >>> @@ -661,7 +681,7 @@ int domain_vpl011_init(struct domain *d, struct
> >> vpl011_init_info *info)
> >>>            }
> >>>        }
> >>>
> >>> -    rc = vgic_reserve_virq(d, GUEST_VPL011_SPI);
> >>> +    rc = vgic_reserve_virq(d, vpl011->virq);
> >>>        if ( !rc )
> >>>        {
> >>>            rc = -EINVAL;
> >>> @@ -673,12 +693,12 @@ int domain_vpl011_init(struct domain *d,
> >>> struct
> >> vpl011_init_info *info)
> >>>        spin_lock_init(&vpl011->lock);
> >>>
> >>>        register_mmio_handler(d, &vpl011_mmio_handler,
> >>> -                          GUEST_PL011_BASE, GUEST_PL011_SIZE, NULL);
> >>> +                          vpl011->base_addr, GUEST_PL011_SIZE,
> >>> + NULL);
> >>
> >> So you are making the assumpption that the UART region will be equal
> >> to (or
> >> bigger) than GUEST_PL011_SIZE. There are definitely UART out where
> >> the MMIO region is smaller than 4K.
> >>
> >
> > Sorry. I got a few confused here, since I am not very familiar with 
> > pl011/UART
> knowledge.
> >
> > Problems will occur when UART region is bigger than GUEST_PL011_SIZE,
> > since we are only considering MMIO region of [vpl011->base_addr, vpl011-
> >base_addr + GUEST_PL011_SIZE], right?
> 
> It is in fact the other way around. The problem will appear if the host UART
> MMIO region is smaller than the one we will emulate for the guest PL011.
> 

Sorry to keep bothering.
Is it that because when the UART MMIO region is smaller than the one we 
emulated,
register(DR, RSR, FR, ...) will not be at the place where we emulated?
  
> >
> > So I shall add the justification like
> > ASSERT(uart->size <= GUEST_PL011_SIZE);
> 
> I think this would want to be a proper check so distro users would get an 
> error
> if they are trying to use this feature on such platform.
> 

Sure, I’ll add the length check.

> Cheers,
> 
> --
> Julien Grall