| Date | Thu, 2 Dec 2021 18:52:15 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v7 10/45] x86/sev: Add support for hypervisor feature VMGEXIT |
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On Wed, Nov 10, 2021 at 04:06:56PM -0600, Brijesh Singh wrote: > +/* > + * The hypervisor features are available from GHCB version 2 onward. > + */ > +static bool get_hv_features(void) > +{ > + u64 val; > + > + sev_hv_features = 0; > + > + if (ghcb_version < 2) > + return false; > + > + sev_es_wr_ghcb_msr(GHCB_MSR_HV_FT_REQ); > + VMGEXIT(); > + > + val = sev_es_rd_ghcb_msr(); > + if (GHCB_RESP_CODE(val) != GHCB_MSR_HV_FT_RESP) > + return false; > + > + sev_hv_features = GHCB_MSR_HV_FT_RESP_VAL(val); > + > + return true; > +}
I still don't like this.
This is more of that run-me-in-the-exception-handler thing while this is purely feature detection stuff which needs to be done exactly once on init.
IOW, that stanza
if (!sev_es_negotiate_protocol()) sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_PROT_UNSUPPORTED);
should be called once in sev_enable() for the decompressor kernel and once in sev_es_init_vc_handling() for kernel proper.
Then you don't need to do any of that sev_hv_features = 0 thing but detect them exactly once and query them as much as you can.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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