Re: [Xen-devel] [PATCH for-next 07/16] xen/arm: Introduce copy_to_guest_phys_flush_dcache

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 23/11/17 18:32, Julien Grall wrote:
> This new function will be used in a follow-up patch to copy data to the guest
> using the IPA (aka guest physical address) and then clean the cache.
>
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>  xen/arch/arm/guestcopy.c           | 10 ++++++++++
>  xen/include/asm-arm/guest_access.h |  6 ++++++
>  2 files changed, 16 insertions(+)
>
> diff --git a/xen/arch/arm/guestcopy.c b/xen/arch/arm/guestcopy.c
> index be53bee559..7958663970 100644
> --- a/xen/arch/arm/guestcopy.c
> +++ b/xen/arch/arm/guestcopy.c
> @@ -110,6 +110,16 @@ unsigned long raw_copy_from_guest(void *to, const void 
> __user *from, unsigned le
>                        COPY_from_guest | COPY_linear);
>  }
>  
> +unsigned long copy_to_guest_phys_flush_dcache(struct domain *d,
> +                                              paddr_t gpa,
> +                                              void *buf,
> +                                              unsigned int len)
> +{
> +    /* P2M is shared between all vCPUs, so the vCPU used does not matter. */

Be very careful with this line of thinking.  It is only works after
DOMCTL_max_vcpus has succeeded, and before that point, it is a latent
NULL pointer dereference.

Also, what about vcpus configured with alternative views?

~Andrew

> +    return copy_guest(buf, gpa, len, d->vcpu[0],
> +                      COPY_to_guest | COPY_ipa | COPY_flush_dcache);
> +}
> +
>  int access_guest_memory_by_ipa(struct domain *d, paddr_t gpa, void *buf,
>                                 uint32_t size, bool is_write)
>  {
> diff --git a/xen/include/asm-arm/guest_access.h 
> b/xen/include/asm-arm/guest_access.h
> index 6796801cfe..224d2a033b 100644
> --- a/xen/include/asm-arm/guest_access.h
> +++ b/xen/include/asm-arm/guest_access.h
> @@ -11,6 +11,12 @@ unsigned long raw_copy_to_guest_flush_dcache(void *to, 
> const void *from,
>  unsigned long raw_copy_from_guest(void *to, const void *from, unsigned len);
>  unsigned long raw_clear_guest(void *to, unsigned len);
>  
> +/* Copy data to guest physical address, then clean the region. */
> +unsigned long copy_to_guest_phys_flush_dcache(struct domain *d,
> +                                              paddr_t phys,
> +                                              void *buf,
> +                                              unsigned int len);
> +
>  int access_guest_memory_by_ipa(struct domain *d, paddr_t ipa, void *buf,
>                                 uint32_t size, bool is_write);
>  


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