This is a note to let you know that I've just added the patch titled
KVM: arm64: vgic-v4: Make the doorbell request robust w.r.t preemption
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-arm64-vgic-v4-make-the-doorbell-request-robust-w.r.t-preemption.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b321c31c9b7b309dcde5e8854b741c8e6a9a05f0 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <maz@xxxxxxxxxx>
Date: Thu, 13 Jul 2023 08:06:57 +0100
Subject: KVM: arm64: vgic-v4: Make the doorbell request robust w.r.t preemption
From: Marc Zyngier <maz@xxxxxxxxxx>
commit b321c31c9b7b309dcde5e8854b741c8e6a9a05f0 upstream.
Xiang reports that VMs occasionally fail to boot on GICv4.1 systems when
running a preemptible kernel, as it is possible that a vCPU is blocked
without requesting a doorbell interrupt.
The issue is that any preemption that occurs between vgic_v4_put() and
schedule() on the block path will mark the vPE as nonresident and *not*
request a doorbell irq. This occurs because when the vcpu thread is
resumed on its way to block, vcpu_load() will make the vPE resident
again. Once the vcpu actually blocks, we don't request a doorbell
anymore, and the vcpu won't be woken up on interrupt delivery.
Fix it by tracking that we're entering WFI, and key the doorbell
request on that flag. This allows us not to make the vPE resident
when going through a preempt/schedule cycle, meaning we don't lose
any state.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 8e01d9a396e6 ("KVM: arm64: vgic-v4: Move the GICv4 residency flow to be driven by vcpu_load/put")
Reported-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
Suggested-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
Tested-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
Co-developed-by: Oliver Upton <oliver.upton@xxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Acked-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230713070657.3873244-1-maz@xxxxxxxxxx
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/include/asm/kvm_host.h | 2 ++
arch/arm64/kvm/arm.c | 6 ++++--
arch/arm64/kvm/vgic/vgic-v3.c | 2 +-
arch/arm64/kvm/vgic/vgic-v4.c | 7 +++++--
include/kvm/arm_vgic.h | 2 +-
5 files changed, 13 insertions(+), 6 deletions(-)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -701,6 +701,8 @@ struct kvm_vcpu_arch {
#define DBG_SS_ACTIVE_PENDING __vcpu_single_flag(sflags, BIT(5))
/* PMUSERENR for the guest EL0 is on physical CPU */
#define PMUSERENR_ON_CPU __vcpu_single_flag(sflags, BIT(6))
+/* WFI instruction trapped */
+#define IN_WFI __vcpu_single_flag(sflags, BIT(7))
/* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -704,13 +704,15 @@ void kvm_vcpu_wfi(struct kvm_vcpu *vcpu)
*/
preempt_disable();
kvm_vgic_vmcr_sync(vcpu);
- vgic_v4_put(vcpu, true);
+ vcpu_set_flag(vcpu, IN_WFI);
+ vgic_v4_put(vcpu);
preempt_enable();
kvm_vcpu_halt(vcpu);
vcpu_clear_flag(vcpu, IN_WFIT);
preempt_disable();
+ vcpu_clear_flag(vcpu, IN_WFI);
vgic_v4_load(vcpu);
preempt_enable();
}
@@ -778,7 +780,7 @@ static int check_vcpu_requests(struct kv
if (kvm_check_request(KVM_REQ_RELOAD_GICv4, vcpu)) {
/* The distributor enable bits were changed */
preempt_disable();
- vgic_v4_put(vcpu, false);
+ vgic_v4_put(vcpu);
vgic_v4_load(vcpu);
preempt_enable();
}
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -749,7 +749,7 @@ void vgic_v3_put(struct kvm_vcpu *vcpu)
{
struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
- WARN_ON(vgic_v4_put(vcpu, false));
+ WARN_ON(vgic_v4_put(vcpu));
vgic_v3_vmcr_sync(vcpu);
--- a/arch/arm64/kvm/vgic/vgic-v4.c
+++ b/arch/arm64/kvm/vgic/vgic-v4.c
@@ -336,14 +336,14 @@ void vgic_v4_teardown(struct kvm *kvm)
its_vm->vpes = NULL;
}
-int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db)
+int vgic_v4_put(struct kvm_vcpu *vcpu)
{
struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
if (!vgic_supports_direct_msis(vcpu->kvm) || !vpe->resident)
return 0;
- return its_make_vpe_non_resident(vpe, need_db);
+ return its_make_vpe_non_resident(vpe, !!vcpu_get_flag(vcpu, IN_WFI));
}
int vgic_v4_load(struct kvm_vcpu *vcpu)
@@ -354,6 +354,9 @@ int vgic_v4_load(struct kvm_vcpu *vcpu)
if (!vgic_supports_direct_msis(vcpu->kvm) || vpe->resident)
return 0;
+ if (vcpu_get_flag(vcpu, IN_WFI))
+ return 0;
+
/*
* Before making the VPE resident, make sure the redistributor
* corresponding to our current CPU expects us here. See the
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -431,7 +431,7 @@ int kvm_vgic_v4_unset_forwarding(struct
int vgic_v4_load(struct kvm_vcpu *vcpu);
void vgic_v4_commit(struct kvm_vcpu *vcpu);
-int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db);
+int vgic_v4_put(struct kvm_vcpu *vcpu);
/* CPU HP callbacks */
void kvm_vgic_cpu_up(void);
Patches currently in stable-queue which might be from maz@xxxxxxxxxx are
queue-6.4/kvm-arm64-timers-use-cnthctl_el2-when-setting-non-cntkctl_el1-bits.patch
queue-6.4/kvm-arm64-disable-preemption-in-kvm_arch_hardware_enable.patch
queue-6.4/kvm-arm64-correctly-handle-page-aging-notifiers-for-unaligned-memslot.patch
queue-6.4/kvm-arm64-vgic-v4-make-the-doorbell-request-robust-w.r.t-preemption.patch
