linux-kernel - [tip: x86/seves] x86/sev-es: Do not unroll string I/O for SEV-ES guests

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Date:   Tue, 02 Feb 2021 15:43:22 -0000
From:   "tip-bot2 for Tom Lendacky" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        Borislav Petkov <bp@...e.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/seves] x86/sev-es: Do not unroll string I/O for SEV-ES guests

The following commit has been merged into the x86/seves branch of tip:

Commit-ID:     62a08a7193dc9107904aaa51a04ba3ba2959f745
Gitweb:        https://git.kernel.org/tip/62a08a7193dc9107904aaa51a04ba3ba2959f745
Author:        Tom Lendacky <thomas.lendacky@....com>
AuthorDate:    Mon, 01 Feb 2021 12:26:27 -06:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Tue, 02 Feb 2021 16:25:05 +01:00

x86/sev-es: Do not unroll string I/O for SEV-ES guests

Under the GHCB specification, SEV-ES guests can support string I/O.
The current #VC handler contains this support, so remove the need to
unroll kernel string I/O operations. This will reduce the number of #VC
exceptions generated as well as the number VM exits for the guest.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/3de04b5b638546ac75d42ba52307fe1a922173d3.1612203987.git.thomas.lendacky@amd.com
---
 arch/x86/mm/mem_encrypt.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index c79e573..d55ea77 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -474,9 +474,10 @@ void __init mem_encrypt_init(void)
 	swiotlb_update_mem_attributes();
 
 	/*
-	 * With SEV, we need to unroll the rep string I/O instructions.
+	 * With SEV, we need to unroll the rep string I/O instructions,
+	 * but SEV-ES supports them through the #VC handler.
 	 */
-	if (sev_active())
+	if (sev_active() && !sev_es_active())
 		static_branch_enable(&sev_enable_key);
 
 	print_mem_encrypt_feature_info();