Messages in this thread | | | Date | Wed, 20 Oct 2021 22:23:06 +0800 | Subject | Re: [PATCH] x86/sev-es: Expose __sev_es_ghcb_hv_call() to call ghcb hv call out of sev code | From | Tianyu Lan <> |
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On 10/20/2021 9:56 PM, Tom Lendacky wrote: > On 10/20/21 8:39 AM, Borislav Petkov wrote: >> On Wed, Oct 20, 2021 at 08:39:59PM +0800, Tianyu Lan wrote: >>> Hyper-V runs paravisor in guest VMPL0 which emulates some functions >>> (e.g, timer, tsc, serial console and so on) via handling VC exception. >>> GHCB pages are allocated and set up by the paravisor and report to Linux >>> guest via MSR register.Hyper-V SEV implementation is unenlightened guest >>> case which doesn't Linux doesn't handle VC and paravisor in the VMPL0 >>> handle it. >> >> Aha, unenlightened. >> >> So why don't you export the original function by doing this (only >> partial diff to show intent only):
This follows Joreg's previous comment and I implemented similar version in the V! patchset([PATCH 05/13] HV: Add Write/Read MSR registers via ghcb page https://lkml.org/lkml/2021/7/28/668). "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."
https://lkml.org/lkml/2021/8/2/375
>> >> --- >> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c >> index f1d513897baf..bfe82f58508f 100644 >> --- a/arch/x86/kernel/sev-shared.c >> +++ b/arch/x86/kernel/sev-shared.c >> @@ -125,7 +125,7 @@ static enum es_result verify_exception_info(struct >> ghcb *ghcb, struct es_em_ctxt >> return ES_VMM_ERROR; >> } >> -static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, >> +static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, bool >> set_ghcb_msr, >> struct es_em_ctxt *ctxt, >> u64 exit_code, u64 exit_info_1, >> u64 exit_info_2) >> @@ -138,7 +138,14 @@ 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 unenlightened guests use a paravisor for communicating >> and >> + * GHCB pages are being allocated by that paravisor which uses a >> + * different MSR and protocol. > > Just to clarify the comment, the paravisor uses the same GHCB MSR and > GHCB protocol, it just can't use __pa() to get the address of the GHCB. > So I expect that the Hyper-V support sets the address properly before > calling this function. > > Thanks, > Tom > >> + */ >> + if (set_ghcb_msr) >> + sev_es_wr_ghcb_msr(__pa(ghcb)); >> + >> VMGEXIT(); >> return verify_exception_info(ghcb, ctxt); >> >>
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