From: Will Deacon <will@kernel.org>
To: kvmarm@lists.linux.dev
Cc: linux-arm-kernel@lists.infradead.org,
Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
Oliver Upton <oliver.upton@linux.dev>
Subject: [PATCH 2/2] KVM: arm64: Use hVHE in pKVM by default on CPUs with VHE support
Date: Wed, 1 May 2024 17:34:00 +0100 [thread overview]
Message-ID: <20240501163400.15838-3-will@kernel.org> (raw)
In-Reply-To: <20240501163400.15838-1-will@kernel.org>
The early command line parsing treats "kvm-arm.mode=protected" as an
alias for "id_aa64mmfr1.vh=0", forcing the use of nVHE so that the host
kernel runs at EL1 with the pKVM hypervisor at EL2.
With the introduction of hVHE support in ad744e8cb346 ("arm64: Allow
arm64_sw.hvhe on command line"), the hypervisor can run using the EL2+0
translation regime. This is interesting for unusual CPUs that have VH
stuck to 1, but also because it opens the possibility of a hypervisor
"userspace" in the distant future which could be used to isolate vCPU
contexts in the hypervisor (see Marc's talk from KVM Forum 2022 [1]).
Repaint the "kvm-arm.mode=protected" alias to map to "arm64_sw.hvhe=1",
which will use hVHE on CPUs that support it and remain with nVHE
otherwise.
[1] https://www.youtube.com/watch?v=1F_Mf2j9eIo
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kernel/pi/idreg-override.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c
index 39c9253fcf23..c20549e43a77 100644
--- a/arch/arm64/kernel/pi/idreg-override.c
+++ b/arch/arm64/kernel/pi/idreg-override.c
@@ -210,7 +210,7 @@ static const struct {
char feature[FTR_ALIAS_OPTION_LEN];
} aliases[] __initconst = {
{ "kvm_arm.mode=nvhe", "arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" },
- { "kvm_arm.mode=protected", "id_aa64mmfr1.vh=0" },
+ { "kvm_arm.mode=protected", "arm64_sw.hvhe=1" },
{ "arm64.nosve", "id_aa64pfr0.sve=0" },
{ "arm64.nosme", "id_aa64pfr1.sme=0" },
{ "arm64.nobti", "id_aa64pfr1.bt=0" },
--
2.45.0.rc0.197.gbae5840b3b-goog
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next prev parent reply other threads:[~2024-05-01 16:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-01 16:33 [PATCH 0/2] Tweaks to the kvm-arm.mode= early cmdline parsing Will Deacon
2024-05-01 16:33 ` [PATCH 1/2] KVM: arm64: Fix hvhe/nvhe early alias parsing Will Deacon
2024-05-01 17:44 ` Oliver Upton
2024-05-02 10:20 ` Will Deacon
2024-05-06 17:35 ` Oliver Upton
2024-05-01 16:34 ` Will Deacon [this message]
2024-05-01 17:47 ` [PATCH 2/2] KVM: arm64: Use hVHE in pKVM by default on CPUs with VHE support Oliver Upton
2024-05-08 6:14 ` [PATCH 0/2] Tweaks to the kvm-arm.mode= early cmdline parsing Marc Zyngier
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