Re: [PATCH v5 09/16] x86/bugs: add lfence mitigation to spectre v2 and no meltdown for Hygon

[Pu Wen]

On 2018/9/5 17:13, Borislav Petkov wrote:
> >   static const char *spectre_v2_strings[] = {
> >   	[SPECTRE_V2_NONE]			= "Vulnerable",
> >   	[SPECTRE_V2_RETPOLINE_MINIMAL]		= "Vulnerable: Minimal generic ASM retpoline",
> > -	[SPECTRE_V2_RETPOLINE_MINIMAL_AMD]	= "Vulnerable: Minimal AMD ASM retpoline",
> > +	[SPECTRE_V2_RETPOLINE_MINIMAL_LFENCE]	= "Vulnerable: Minimal LFENCE ASM retpoline",
> >   	[SPECTRE_V2_RETPOLINE_GENERIC]		= "Mitigation: Full generic retpoline",
> > -	[SPECTRE_V2_RETPOLINE_AMD]		= "Mitigation: Full AMD retpoline",
> > +	[SPECTRE_V2_RETPOLINE_LFENCE]		= "Mitigation: Full LFENCE retpoline",
> >   	[SPECTRE_V2_IBRS_ENHANCED]		= "Mitigation: Enhanced IBRS",
> >   };
>
> This is user-visible and with all the back'n'forth and backporting
> and the whole security fiasco, I don't want to have another source of
> confusion. You'll have to live with it saying "AMD" in dmesg
....
> > @@ -272,7 +272,7 @@ static const struct {
> >   	{ "off",               SPECTRE_V2_CMD_NONE,              false },
> >   	{ "on",                SPECTRE_V2_CMD_FORCE,             true },
> >   	{ "retpoline",         SPECTRE_V2_CMD_RETPOLINE,         false },
> > -	{ "retpoline,amd",     SPECTRE_V2_CMD_RETPOLINE_AMD,     false },
> > +	{ "retpoline,lfence",     SPECTRE_V2_CMD_RETPOLINE_LFENCE,     false },
> >   	{ "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
> >   	{ "auto",              SPECTRE_V2_CMD_AUTO,              false },
> >   };
>
> This even more so. Those are command line strings which we're still
> communicating to people, even. So no, it needs to remain "retpoline,amd"
> on Hygon.
>
> And then to not confuse people staring at the code either, we can drop
> this change too:
>
> -     SPECTRE_V2_CMD_RETPOLINE_AMD,
> +     SPECTRE_V2_CMD_RETPOLINE_LFENCE,
>
> Which leaves this patch only with the addition of the vendor tests. The
> other stuff you can drop.

That's reasonable. To avoid the confusion, will only leave the vendor
testing for Hygon and drop the other changes, which also minimize the
code modification.

--
Regards,
Pu Wen