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KVM: arm64: Use hVHE in pKVM by default on CPUs with VHE support

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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 ad744e8cb3 ("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>
Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240501163400.15838-3-will@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Will Deacon 2024-05-01 17:34:00 +01:00 • committed by Marc Zyngier
parent 3c142f9d02
commit 5053c3f051
1 changed files with 1 additions and 1 deletions
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2
arch/arm64/kernel/pi/idreg-override.c
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@ -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" },