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.
