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KVM: arm64: Take a protected vCPU's TWI and TWE only at vCPU load

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Commit 06499de8f9 ("KVM: arm64: Skip fixed-feature state flush for
protected vCPUs") moved the copy of the host's TWI and TWE in
flush_hyp_vcpu() into the non-protected branch: a protected vCPU takes
them in __pkvm_vcpu_load() instead, and only VSE comes from the host on
each entry.

Commit 04447b95c6 ("KVM: arm64: Use the host's HCR_EL2 for
non-protected VMs in pKVM") was written against the old code, where
both VM types took TWI, TWE and VSE on each entry, and kept that for a
protected VM as PKVM_HCR_EL2_HOST_PVM. The merge of the two applies
PKVM_HCR_EL2_HOST_PVM in the common path, so a protected vCPU takes TWI
and TWE from the host's vCPU on every entry again.

That doesn't change what a protected guest runs with today: once the
vCPU is initialised, the host only changes TWI and TWE in
vcpu_set_wfx_traps(), which pkvm_vcpu_load() calls right before
__pkvm_vcpu_load(). But it undoes part of 06499de8f9, and has EL2
read a protected vCPU's trap configuration from host memory on every
entry, which nothing needs.

Make PKVM_HCR_EL2_HOST_PVM VSE alone and add TWI and TWE to
PKVM_HCR_EL2_HOST_NPVM, so that each mask again lists what EL2 takes
from the host on each entry for its VM type. A non-protected VM takes
the same bits as before. Say in the comments that a protected vCPU's
TWI and TWE come at vCPU load.

llminus, an LLM-assisted merge conflict resolution tool, found the
difference while resolving the same conflict in an integration tree.

Fixes: 439d8f9cb0 ("Merge tag 'kvmarm-7.4' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD")
Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@kernel.org>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20261017165204.3343275-1-sashal@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Sasha Levin 2026-10-17 12:52:04 -04:00 committed by Marc Zyngier
parent 814607cd40
commit 5b34f0b4ad
2 changed files with 11 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/arm64/kvm/hyp/include/nvhe/pkvm.h
View File

@ -14,13 +14,14 @@
#include <nvhe/spinlock.h>
/*
* HCR_EL2 bits EL2 takes from the host on each entry, per VM type. The rest
* are EL2's own and nothing the host sets there reaches the guest.
* HCR_EL2 bits EL2 takes from the host on each entry, per VM type. A protected
* VM also takes TWI and TWE, at vCPU load. The rest are EL2's own and nothing
* the host sets there reaches the guest.
*/
#define PKVM_HCR_EL2_HOST_PVM (HCR_EL2_TWI | HCR_EL2_TWE | HCR_EL2_VSE)
#define PKVM_HCR_EL2_HOST_NPVM (PKVM_HCR_EL2_HOST_PVM | HCR_EL2_VI | HCR_EL2_VF | \
HCR_EL2_TVM | HCR_EL2_TID2 | HCR_EL2_TID4 | \
HCR_EL2_TID5 | HCR_EL2_TTLBOS)
#define PKVM_HCR_EL2_HOST_PVM HCR_EL2_VSE
#define PKVM_HCR_EL2_HOST_NPVM (PKVM_HCR_EL2_HOST_PVM | HCR_EL2_TWI | HCR_EL2_TWE | \
HCR_EL2_VI | HCR_EL2_VF | HCR_EL2_TVM | HCR_EL2_TID2 | \
HCR_EL2_TID4 | HCR_EL2_TID5 | HCR_EL2_TTLBOS)
/*
* Holds the relevant data for maintaining the vcpu state completely at hyp.

5
arch/arm64/kvm/hyp/nvhe/pkvm.c
View File

@ -38,7 +38,10 @@ unsigned int kvm_host_sve_max_vl;
*/
static DEFINE_PER_CPU(struct pkvm_hyp_vcpu *, loaded_hyp_vcpu);
/* The PKVM_HCR_EL2_HOST_{PVM,NPVM} bits of this value come from the host on each entry. */
/*
* The PKVM_HCR_EL2_HOST_{PVM,NPVM} bits of this value come from the host on
* each entry, and a protected vCPU's TWI and TWE at vCPU load.
*/
static void pkvm_vcpu_reset_hcr(struct kvm_vcpu *vcpu)
{
vcpu->arch.hcr_el2 = HCR_GUEST_FLAGS;