Re: [XEN PATCH v12 4/7] x86/domctl: Add hypercall to set the access of x86 gsi

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 8 Jul 2024, Jiqian Chen wrote:
> Some type of domains don't have PIRQs, like PVH, it doesn't do
> PHYSDEVOP_map_pirq for each gsi. When passthrough a device
> to guest base on PVH dom0, callstack
> pci_add_dm_done->XEN_DOMCTL_irq_permission will fail at function
> domain_pirq_to_irq, because PVH has no mapping of gsi, pirq and
> irq on Xen side.
> What's more, current hypercall XEN_DOMCTL_irq_permission requires
> passing in pirq to set the access of irq, it is not suitable for
> dom0 that doesn't have PIRQs.
> 
> So, add a new hypercall XEN_DOMCTL_gsi_permission to grant/deny
> the permission of irq(translate from x86 gsi) to dumU when dom0
> has no PIRQs.
> 
> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
> Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
> ---
> CC: Daniel P . Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> Remaining comment @Daniel P . Smith:
> +        ret = -EPERM;
> +        if ( !irq_access_permitted(currd, irq) ||
> +             xsm_irq_permission(XSM_HOOK, d, irq, access_flag) )
> +            goto gsi_permission_out;
> Is it okay to issue the XSM check using the translated value, 
> not the one that was originally passed into the hypercall?
> ---
>  xen/arch/x86/domctl.c              | 32 ++++++++++++++++++++++++++++++
>  xen/arch/x86/include/asm/io_apic.h |  2 ++
>  xen/arch/x86/io_apic.c             | 17 ++++++++++++++++
>  xen/arch/x86/mpparse.c             |  5 ++---
>  xen/include/public/domctl.h        |  9 +++++++++
>  xen/xsm/flask/hooks.c              |  1 +
>  6 files changed, 63 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> index 9190e11faaa3..4e9e4c4cfed3 100644
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -36,6 +36,7 @@
>  #include <asm/xstate.h>
>  #include <asm/psr.h>
>  #include <asm/cpu-policy.h>
> +#include <asm/io_apic.h>
>  
>  static int update_domain_cpu_policy(struct domain *d,
>                                      xen_domctl_cpu_policy_t *xdpc)
> @@ -237,6 +238,37 @@ long arch_do_domctl(
>          break;
>      }
>  
> +    case XEN_DOMCTL_gsi_permission:
> +    {
> +        int irq;
> +        unsigned int gsi = domctl->u.gsi_permission.gsi;
> +        uint8_t access_flag = domctl->u.gsi_permission.access_flag;
> +
> +        /* Check all bits and pads are zero except lowest bit */
> +        ret = -EINVAL;
> +        if ( access_flag & ( ~XEN_DOMCTL_GSI_PERMISSION_MASK ) )
> +            goto gsi_permission_out;
> +        for ( i = 0; i < ARRAY_SIZE(domctl->u.gsi_permission.pad); ++i )
> +            if ( domctl->u.gsi_permission.pad[i] )
> +                goto gsi_permission_out;
> +
> +        if ( gsi > highest_gsi() || (irq = gsi_2_irq(gsi)) <= 0 )

gsi is unsigned int but it is passed to gsi_2_irq which takes an int as
parameter. If gsi >= INT32_MAX we have a problem. I think we should
explicitly check for the possible overflow and return error in that
case.


> +            goto gsi_permission_out;
> +
> +        ret = -EPERM;
> +        if ( !irq_access_permitted(currd, irq) ||
> +             xsm_irq_permission(XSM_HOOK, d, irq, access_flag) )
> +            goto gsi_permission_out;
> +
> +        if ( access_flag )
> +            ret = irq_permit_access(d, irq);
> +        else
> +            ret = irq_deny_access(d, irq);
> +
> +    gsi_permission_out:
> +        break;
> +    }
> +
>      case XEN_DOMCTL_getpageframeinfo3:
>      {
>          unsigned int num = domctl->u.getpageframeinfo3.num;
> diff --git a/xen/arch/x86/include/asm/io_apic.h 
> b/xen/arch/x86/include/asm/io_apic.h
> index 78268ea8f666..7e86d8337758 100644
> --- a/xen/arch/x86/include/asm/io_apic.h
> +++ b/xen/arch/x86/include/asm/io_apic.h
> @@ -213,5 +213,7 @@ unsigned highest_gsi(void);
>  
>  int ioapic_guest_read( unsigned long physbase, unsigned int reg, u32 *pval);
>  int ioapic_guest_write(unsigned long physbase, unsigned int reg, u32 val);
> +int mp_find_ioapic(int gsi);
> +int gsi_2_irq(int gsi);
>  
>  #endif
> diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
> index d2a313c4ac72..5968c8055671 100644
> --- a/xen/arch/x86/io_apic.c
> +++ b/xen/arch/x86/io_apic.c
> @@ -955,6 +955,23 @@ static int pin_2_irq(int idx, int apic, int pin)
>      return irq;
>  }
>  
> +int gsi_2_irq(int gsi)
> +{
> +    int ioapic, pin, irq;
> +
> +    ioapic = mp_find_ioapic(gsi);
> +    if ( ioapic < 0 )
> +        return -EINVAL;
> +
> +    pin = gsi - io_apic_gsi_base(ioapic);
> +
> +    irq = apic_pin_2_gsi_irq(ioapic, pin);
> +    if ( irq <= 0 )
> +        return -EINVAL;
> +
> +    return irq;
> +}
> +
>  static inline int IO_APIC_irq_trigger(int irq)
>  {
>      int apic, idx, pin;
> diff --git a/xen/arch/x86/mpparse.c b/xen/arch/x86/mpparse.c
> index d8ccab2449c6..7786a3337760 100644
> --- a/xen/arch/x86/mpparse.c
> +++ b/xen/arch/x86/mpparse.c
> @@ -841,8 +841,7 @@ static struct mp_ioapic_routing {
>  } mp_ioapic_routing[MAX_IO_APICS];
>  
>  
> -static int mp_find_ioapic (
> -     int                     gsi)
> +int mp_find_ioapic(int gsi)
>  {
>       unsigned int            i;
>  
> @@ -914,7 +913,7 @@ void __init mp_register_ioapic (
>       return;
>  }
>  
> -unsigned __init highest_gsi(void)
> +unsigned highest_gsi(void)
>  {
>       unsigned x, res = 0;
>       for (x = 0; x < nr_ioapics; x++)
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index 2a49fe46ce25..877e35ab1376 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -464,6 +464,13 @@ struct xen_domctl_irq_permission {
>      uint8_t pad[3];
>  };
>  
> +/* XEN_DOMCTL_gsi_permission */
> +struct xen_domctl_gsi_permission {
> +    uint32_t gsi;
> +#define XEN_DOMCTL_GSI_PERMISSION_MASK 1
> +    uint8_t access_flag;    /* flag to specify enable/disable of x86 gsi 
> access */
> +    uint8_t pad[3];
> +};
>  
>  /* XEN_DOMCTL_iomem_permission */
>  struct xen_domctl_iomem_permission {
> @@ -1306,6 +1313,7 @@ struct xen_domctl {
>  #define XEN_DOMCTL_get_paging_mempool_size       85
>  #define XEN_DOMCTL_set_paging_mempool_size       86
>  #define XEN_DOMCTL_dt_overlay                    87
> +#define XEN_DOMCTL_gsi_permission                88
>  #define XEN_DOMCTL_gdbsx_guestmemio            1000
>  #define XEN_DOMCTL_gdbsx_pausevcpu             1001
>  #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
> @@ -1328,6 +1336,7 @@ struct xen_domctl {
>          struct xen_domctl_setdomainhandle   setdomainhandle;
>          struct xen_domctl_setdebugging      setdebugging;
>          struct xen_domctl_irq_permission    irq_permission;
> +        struct xen_domctl_gsi_permission    gsi_permission;
>          struct xen_domctl_iomem_permission  iomem_permission;
>          struct xen_domctl_ioport_permission ioport_permission;
>          struct xen_domctl_hypercall_init    hypercall_init;
> diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
> index 5e88c71b8e22..a5b134c91101 100644
> --- a/xen/xsm/flask/hooks.c
> +++ b/xen/xsm/flask/hooks.c
> @@ -685,6 +685,7 @@ static int cf_check flask_domctl(struct domain *d, int 
> cmd)
>      case XEN_DOMCTL_shadow_op:
>      case XEN_DOMCTL_ioport_permission:
>      case XEN_DOMCTL_ioport_mapping:
> +    case XEN_DOMCTL_gsi_permission:
>  #endif
>  #ifdef CONFIG_HAS_PASSTHROUGH
>      /*
> -- 
> 2.34.1
>