Re: [Xen-devel] [PATCH 2/2] x86/dmar: zap DMAR signature for dom0 once in TBOOT case

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.08.18 at 05:32, <zhenzhong.duan@xxxxxxxxxx> wrote:
> When TBOOT enabled, acpi_parse_dmar() zap a copy of DMAR table rather
> than the real table, so make it controled by config option based on the
> fact that we already have done the real zapping in tboot_parse_dmar_table().

Is this just a cosmetic change, or is there any harm done by the extra
zapping?

> As said above, acpi_parse_dmar() doesn't zaps APCI DMAR signature in
> real TXT heap table, fix the stale comments.
> 
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
> ---
>  xen/arch/x86/tboot.c               |    3 +--
>  xen/drivers/passthrough/vtd/dmar.c |    2 ++
>  2 files changed, 3 insertions(+), 2 deletions(-)

You've again failed to Cc maintainers (included now).

Jan

> --- a/xen/arch/x86/tboot.c
> +++ b/xen/arch/x86/tboot.c
> @@ -490,8 +490,7 @@ int __init tboot_parse_dmar_table(acpi_table_handler 
> dmar_handler)
>      rc = dmar_handler(dmar_table);
>      xfree(dmar_table);
>  
> -    /* acpi_parse_dmar() zaps APCI DMAR signature in TXT heap table */
> -    /* but dom0 will read real table, so must zap it there too */
> +    /* Dom0 will read real DMAR table, so must zap it there */
>      acpi_dmar_zap();
>  
>      return rc;
> --- a/xen/drivers/passthrough/vtd/dmar.c
> +++ b/xen/drivers/passthrough/vtd/dmar.c
> @@ -866,8 +866,10 @@ static int __init acpi_parse_dmar(struct 
> acpi_table_header *table)
>      }
>  
>  out:
> +#ifndef CONFIG_TBOOT
>      /* Zap ACPI DMAR signature to prevent dom0 using vt-d HW. */
>      acpi_dmar_zap();
> +#endif
>      return ret;
>  }
>  



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