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

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Tuesday, August 21, 2018 8:32 PM
> 
> >>> 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.
> 

yes, a better description is expected here.

Thanks
Kevin

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