Re: [RFC PATCH 1/2] mem_access: Fix npfec.kind propagation

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 26/09/18 17:47, George Dunlap wrote:
> The name of the "with_gla" flag is confusing; it has nothing to do
> with the existence or lack thereof of a faulting GLA, but rather where
> the fault originated.  The npfec.kind value is always valid, and
> should thus be propagated, regardless of whether gla_valid is set or
> not.
>
> In particular, gla_valid will never be set on AMD systems; but
> npfec.kind will still be valid and should still be propagated.
>
> Signed-off-by: Alexandru Isaila <aisaila@bitdefender.com>
> Signed-off-by: George Dunlap <george.dunlap@citrix.com>
> ---
> CC: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Jan Beulich <jbeulich@suse.com>
> CC: Tim Deegan <tim@xen.org>
> CC: Tamas K Lengyel <tamas.lengyel@zentific.com>
> CC: Razvan Cojocaru <rcojocaru@bitdefender.com>
> ---
>  xen/arch/x86/mm/mem_access.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/xen/arch/x86/mm/mem_access.c b/xen/arch/x86/mm/mem_access.c
> index d9e64fcbb9..699a315076 100644
> --- a/xen/arch/x86/mm/mem_access.c
> +++ b/xen/arch/x86/mm/mem_access.c
> @@ -232,12 +232,12 @@ bool p2m_mem_access_check(paddr_t gpa, unsigned long gla,
>          {
>              req->u.mem_access.flags |= MEM_ACCESS_GLA_VALID;
>              req->u.mem_access.gla = gla;
> -
> -            if ( npfec.kind == npfec_kind_with_gla )
> -                req->u.mem_access.flags |= MEM_ACCESS_FAULT_WITH_GLA;
> -            else if ( npfec.kind == npfec_kind_in_gpt )
> -                req->u.mem_access.flags |= MEM_ACCESS_FAULT_IN_GPT;
>          }
> +
> +        if ( npfec.kind == npfec_kind_with_gla )
> +            req->u.mem_access.flags |= MEM_ACCESS_FAULT_WITH_GLA;
> +        else if ( npfec.kind == npfec_kind_in_gpt )
> +            req->u.mem_access.flags |= MEM_ACCESS_FAULT_IN_GPT;

Nit.  Newline here please, as it is not logically related with the block
below.

~Andrew

>          req->u.mem_access.flags |= npfec.read_access    ? MEM_ACCESS_R : 0;
>          req->u.mem_access.flags |= npfec.write_access   ? MEM_ACCESS_W : 0;
>          req->u.mem_access.flags |= npfec.insn_fetch     ? MEM_ACCESS_X : 0;


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