Messages in this thread | | | Subject | Re: [PATCH v7 10/45] x86/sev: Add support for hypervisor feature VMGEXIT | From | Brijesh Singh <> | Date | Mon, 6 Dec 2021 09:15:59 -0600 |
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On 12/2/21 11:52 AM, Borislav Petkov wrote: > 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. >
I will look into it, I will improve the sev_enable() to call GHCB MSR protocol query the version and feature.
> 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. >
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