On Wed, Jul 28, 2021 at 10:52:20AM -0400, Tianyu Lan wrote:
> +void hv_ghcb_msr_write(u64 msr, u64 value)
> +{
> + union hv_ghcb *hv_ghcb;
> + void **ghcb_base;
> + unsigned long flags;
> +
> + if (!ms_hyperv.ghcb_base)
> + return;
> +
> + WARN_ON(in_nmi());
> +
> + local_irq_save(flags);
> + ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
> + hv_ghcb = (union hv_ghcb *)*ghcb_base;
> + if (!hv_ghcb) {
> + local_irq_restore(flags);
> + return;
> + }
> +
> + memset(hv_ghcb, 0x00, HV_HYP_PAGE_SIZE);
Do you really need to zero out the whole 4k? The validation bitmap
should be enough, there are no secrets on the page anyway.
Same in hv_ghcb_msr_read().
> +enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
> + struct es_em_ctxt *ctxt,
> + u64 exit_code, u64 exit_info_1,
> + u64 exit_info_2)
> {
> enum es_result ret;
>
> @@ -109,7 +109,16 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
> ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
> ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
>
> - sev_es_wr_ghcb_msr(__pa(ghcb));
> + /*
> + * Hyper-V runs paravisor with SEV. Ghcb page is allocated by
> + * paravisor and not needs to be updated in the Linux guest.
> + * Otherwise, the ghcb page's PA reported by paravisor is above
> + * VTOM. Hyper-V use this function with NULL for ctxt point and
> + * skip setting ghcb page in such case.
> + */
> + if (ctxt)
> + sev_es_wr_ghcb_msr(__pa(ghcb));
No, do not make this function work with ctxt==NULL. Instead, factor out
a helper function which contains what Hyper-V needs and use that in
sev_es_ghcb_hv_call() and Hyper-V code.
> +union hv_ghcb {
> + struct ghcb ghcb;
> +} __packed __aligned(PAGE_SIZE);
I am curious what this will end up being good for.
