Re: [Xen-devel] [PATCH v6 05/12] x86/domctl: Handle ACPI access from domctl

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 01/03/2017 02:04 PM, Boris Ostrovsky wrote:
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
> Changes in v6:
> * Adjustments to to patch 4 changes.
> * Added a spinlock for VCPU map access
> * Return an error on guest trying to write VCPU map
snip
> -static int acpi_cpumap_access_common(struct domain *d, bool is_write,
> -                                     unsigned int port,
> +static int acpi_cpumap_access_common(struct domain *d, bool is_guest_access,
> +                                     bool is_write, unsigned int port,
>                                        unsigned int bytes, uint32_t *val)
>   {
>       unsigned int first_byte = port - XEN_ACPI_CPU_MAP;
> +    int rc = X86EMUL_OKAY;
>
>       BUILD_BUG_ON(XEN_ACPI_CPU_MAP + XEN_ACPI_CPU_MAP_LEN
>                    > ACPI_GPE0_BLK_ADDRESS_V1);
>
> +    spin_lock(&d->arch.hvm_domain.acpi_lock);
> +
>       if ( !is_write )
>       {
>           uint32_t mask = (bytes < 4) ? ~0U << (bytes * 8) : 0;
> @@ -32,23 +37,61 @@ static int acpi_cpumap_access_common(struct domain *d, bool 
> is_write,
>               memcpy(val, (uint8_t *)d->avail_vcpus + first_byte,
>                      min(bytes, ((d->max_vcpus + 7) / 8) - first_byte));
>       }
> +    else if ( !is_guest_access )
> +        memcpy((uint8_t *)d->avail_vcpus + first_byte, val,
> +               min(bytes, ((d->max_vcpus + 7) / 8) - first_byte));
>       else
>           /* Guests do not write CPU map */
> -        return X86EMUL_UNHANDLEABLE;
> +        rc = X86EMUL_UNHANDLEABLE;
>
> -    return X86EMUL_OKAY;
> +    spin_unlock(&d->arch.hvm_domain.acpi_lock);
> +
> +    return rc;
>   }
>
>   int hvm_acpi_domctl_access(struct domain *d,
>                              const struct xen_domctl_acpi_access *access)
>   {
> -    return -ENOSYS;
> +    unsigned int bytes, i;
> +    uint32_t val = 0;
> +    uint8_t *ptr = (uint8_t *)&val;
> +    int rc;
> +    bool is_write = (access->rw == XEN_DOMCTL_ACPI_WRITE) ? true : false;
> +
> +    if ( has_acpi_dm_ff(d) )
> +        return -EOPNOTSUPP;
> +
> +    if ( access->space_id != XEN_ACPI_SYSTEM_IO )
> +        return -EINVAL;
> +
> +    if ( !((access->address >= XEN_ACPI_CPU_MAP) &&
> +           (access->address < XEN_ACPI_CPU_MAP + XEN_ACPI_CPU_MAP_LEN)) )
> +        return -ENODEV;
> +
> +    for ( i = 0; i < access->width; i += sizeof(val) )
> +    {
> +        bytes = (access->width - i > sizeof(val)) ?
> +            sizeof(val) : access->width - i;
> +
> +        if ( is_write && copy_from_guest_offset(ptr, access->val, i, bytes) )
> +            return -EFAULT;
> +
> +        rc = acpi_cpumap_access_common(d, false, is_write,
> +                                       access->address, bytes, &val);
While I'm looking at this code...
This doesn't work if access->width > sizeof(val) (4 bytes). The same 
value (access->address) is always passed into acpi_cpumap_access_common 
for 'port' and this is used as an offset into the avail_cpus array. So 
the offset is unchanged and only the first 4 bytes of avail_cpus ever 
gets changed.
--
Ross Lagerwall

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