Re: [Xen-devel] [PATCH v3 2/2] x86/dmar: zap DMAR signature for dom0 once in TBOOT case

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.08.18 at 11:11, <zhenzhong.duan@xxxxxxxxxx> wrote:
> @@ -490,10 +488,6 @@ 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 */
> -    acpi_dmar_zap();

Interesting - now you remove the other one. I think this is actually correct,
but understanding why could _again_ have been a lot easier with a better
description. Afaict commit 6c298ecc1f ("vtd: Reinstate ACPI DMAR on
system shutdown or S3/S4/S5") did everything for this call to be
unnecessary, except for invoking the function from acpi_parse_dmar(),
which 123c779379 ("VTd/dmar: Tweak how the DMAR table is clobbered")
added several years later.

Jan



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