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Re: [RFC PATCH V3 01/11] x86/HV: Initialize GHCB page in Isolation VM

Hi Joerg:
        Thanks for your review.

On 6/9/2021 8:38 PM, Joerg Roedel wrote:
On Sun, May 30, 2021 at 11:06:18AM -0400, Tianyu Lan wrote:
From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>

Hyper-V exposes GHCB page via SEV ES GHCB MSR for SNP guest
to communicate with hypervisor. Map GHCB page for all
cpus to read/write MSR register and submit hvcall request
via GHCB.

Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
  arch/x86/hyperv/hv_init.c       | 60 ++++++++++++++++++++++++++++++---
  arch/x86/include/asm/mshyperv.h |  2 ++
  include/asm-generic/mshyperv.h  |  2 ++
  3 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index bb0ae4b5c00f..dc74d01cb859 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -60,6 +60,9 @@ static int hv_cpu_init(unsigned int cpu)
        struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
        void **input_arg;
        struct page *pg;
+       u64 ghcb_gpa;
+       void *ghcb_va;
+       void **ghcb_base;

Any reason you can't reuse the SEV-ES support code in the Linux kernel?
It already has code to setup GHCBs for all vCPUs.

I see that you don't need #VC handling in your SNP VMs because of the
paravisor running underneath it, but just re-using the GHCB setup code
shouldn't be too hard.

Thanks for your suggestion. I will have a try to use SEV-ES code.



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