Re: [Xen-devel] [PATCH v4 02/39] arm/p2m: Add first altp2m HVMOP stubs

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Sergej,

On 30/08/17 19:32, Sergej Proskurin wrote:
> This commit copies and extends the altp2m-related code from x86 to ARM.
> Functions that are no yet supported notify the caller or print a BUG
> message stating their absence.
I am still concerned on the locking differing between x86 and Arm 
(likely the former is wrong) and for maintain POV in the future.
Last year you said you were working on getting do_altp2m_op common 
between x86 and Arm. What's the status?
> diff --git a/xen/arch/arm/hvm.c b/xen/arch/arm/hvm.c
> index a56b3fe3fb..042bdda979 100644
> --- a/xen/arch/arm/hvm.c
> +++ b/xen/arch/arm/hvm.c
> @@ -31,6 +31,99 @@
>   
>   #include <asm/hypercall.h>
>   
> +#include <asm/altp2m.h>
> +
> +static int do_altp2m_op(XEN_GUEST_HANDLE_PARAM(void) arg)
> +{
> +    struct xen_hvm_altp2m_op a;
> +    struct domain *d = NULL;
> +    uint64_t mode;
> +    int rc = 0;
> +
> +    if ( copy_from_guest(&a, arg, 1) )
> +        return -EFAULT;
> +
> +    if ( a.pad1 || a.pad2 ||
> +         (a.version != HVMOP_ALTP2M_INTERFACE_VERSION) ||
> +         (a.cmd < HVMOP_altp2m_get_domain_state) ||
> +         (a.cmd > HVMOP_altp2m_change_gfn) )
That exactly support my view above. You resent a series after a year and 
don't even look at what changed in x86.
I don't expect any better improvement as people will add more features 
in each side.
[...]

> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 8dfc1d1ec2..0991a0a79d 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -145,6 +145,9 @@ struct arch_domain
>       struct {
>           uint8_t privileged_call_enabled : 1;
>       } monitor;
> +
> +    /* altp2m: allow multiple copies of the host's p2m */
> +    bool altp2m_active;
Does it have to be in arch_domain? Can't this be done in common code?

>   }  __cacheline_aligned;
>   
>   struct arch_vcpu
Cheers,

--
Julien Grall

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