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From: Borislav Petkov <bp@alien8.de>
To: Tianyu Lan <ltykernel@gmail.com>
Cc: Tianyu Lan <Tianyu.Lan@microsoft.com>,
	kys@microsoft.com, haiyangz@microsoft.com,
	sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com,
	tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
	hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org,
	peterz@infradead.org, davem@davemloft.net, kuba@kernel.org,
	gregkh@linuxfoundation.org, arnd@arndb.de, jroedel@suse.de,
	brijesh.singh@amd.com, thomas.lendacky@amd.com,
	pgonda@google.com, akpm@linux-foundation.org,
	kirill.shutemov@linux.intel.com, rppt@kernel.org, tj@kernel.org,
	aneesh.kumar@linux.ibm.com, saravanand@fb.com,
	hannes@cmpxchg.org, rientjes@google.com,
	michael.h.kelley@microsoft.com, linux-arch@vger.kernel.org,
	linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, vkuznets@redhat.com,
	konrad.wilk@oracle.com, hch@lst.de, robin.murphy@arm.com,
	joro@8bytes.org, parri.andrea@gmail.com, dave.hansen@intel.com
Subject: Re: [PATCH] x86/sev-es: Expose __sev_es_ghcb_hv_call() to call ghcb hv call out of sev code
Date: Wed, 20 Oct 2021 15:39:38 +0200	[thread overview]
Message-ID: <YXAcGtxe08XiHBFH@zn.tnic> (raw)
In-Reply-To: <c5b55d93-14c4-81cf-e999-71ad5d6a1b41@gmail.com>

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):

---
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.
+	 */
+	if (set_ghcb_msr)
+		sev_es_wr_ghcb_msr(__pa(ghcb));
+
 	VMGEXIT();
 
 	return verify_exception_info(ghcb, ctxt);


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  reply	other threads:[~2021-10-20 13:39 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-06  6:36 [PATCH V7 0/9] x86/Hyper-V: Add Hyper-V Isolation VM support(First part) Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 1/9] x86/hyperv: Initialize GHCB page in Isolation VM Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 2/9] x86/hyperv: Initialize shared memory boundary in the " Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 3/9] x86/hyperv: Add new hvcall guest address host visibility support Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 4/9] Drivers: hv: vmbus: Mark vmbus ring buffer visible to host in Isolation VM Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 5/9] x86/sev-es: Expose __sev_es_ghcb_hv_call() to call ghcb hv call out of sev code Tianyu Lan
2021-10-11 14:42   ` Tianyu Lan
2021-10-11 17:22     ` Borislav Petkov
2021-10-12 14:13       ` Tianyu Lan
2021-10-13 14:24       ` Tianyu Lan
2021-10-18 12:19         ` Tianyu Lan
2021-10-19 13:57           ` Borislav Petkov
2021-10-20  6:23           ` [PATCH] " Tianyu Lan
2021-10-20  9:59             ` Borislav Petkov
2021-10-20 12:39               ` Tianyu Lan
2021-10-20 13:39                 ` Borislav Petkov [this message]
2021-10-20 13:56                   ` Tom Lendacky
2021-10-20 14:23                     ` Tianyu Lan
2021-10-20 14:39                       ` Borislav Petkov
2021-10-20 15:09                         ` Tianyu Lan
2021-10-20 16:24                           ` Borislav Petkov
2021-10-21 15:42                             ` Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 6/9] x86/hyperv: Add Write/Read MSR registers via ghcb page Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 7/9] x86/hyperv: Add ghcb hvcall support for SNP VM Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 8/9] Drivers: hv: vmbus: Add SNP support for VMbus channel initiate message Tianyu Lan
2021-10-06  6:36 ` [PATCH V7 9/9] Drivers: hv : vmbus: Initialize VMbus ring buffer for Isolation VM Tianyu Lan

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