Hi Yury,

On Thu, Nov 30, 2017 at 09:33:30PM +0300, Yury Norov wrote:

On Thu, Oct 12, 2017 at 12:41:41PM +0200, Christoffer Dall wrote:

quoted

We can finally get completely rid of any calls to the VGICv3
save/restore functions when the AP lists are empty on VHE systems.  This
requires carefully factoring out trap configuration from saving and
restoring state, and carefully choosing what to do on the VHE and
non-VHE path.

One of the challenges is that we cannot save/restore the VMCR lazily
because we can only write the VMCR when ICC_SRE_EL1.SRE is cleared when
emulating a GICv2-on-GICv3, since otherwise all Group-0 interrupts end
up being delivered as FIQ.

To solve this problem, and still provide fast performance in the fast
path of exiting a VM when no interrupts are pending (which also
optimized the latency for actually delivering virtual interrupts coming
from physical interrupts), we orchestrate a dance of only doing the
activate/deactivate traps in vgic load/put for VHE systems (which can
have ICC_SRE_EL1.SRE cleared when running in the host), and doing the
configuration on every round-trip on non-VHE systems.

Signed-off-by: Christoffer Dall <redacted>
---
 arch/arm/include/asm/kvm_hyp.h   |   2 +
 arch/arm/kvm/hyp/switch.c        |   8 ++-
 arch/arm64/include/asm/kvm_hyp.h |   2 +
 arch/arm64/kvm/hyp/switch.c      |   8 ++-
 virt/kvm/arm/hyp/vgic-v3-sr.c    | 116 +++++++++++++++++++++++++--------------
 virt/kvm/arm/vgic/vgic-v3.c      |   6 ++
 virt/kvm/arm/vgic/vgic.c         |   7 +--
 7 files changed, 101 insertions(+), 48 deletions(-)

[...]

quoted

diff --git a/virt/kvm/arm/hyp/vgic-v3-sr.c b/virt/kvm/arm/hyp/vgic-v3-sr.c
index ed5da75..34d71d2 100644
--- a/virt/kvm/arm/hyp/vgic-v3-sr.c
+++ b/virt/kvm/arm/hyp/vgic-v3-sr.c

@@ -208,15 +208,15 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
 	u64 used_lrs = vcpu->arch.vgic_cpu.used_lrs;
-	u64 val;
 
 	/*
 	 * Make sure stores to the GIC via the memory mapped interface
-	 * are now visible to the system register interface.
+	 * are now visible to the system register interface when reading the
+	 * LRs, and when reading back the VMCR on non-VHE systems.
 	 */
-	if (!cpu_if->vgic_sre) {
-		dsb(st);
-		cpu_if->vgic_vmcr = read_gicreg(ICH_VMCR_EL2);
+	if (used_lrs || !has_vhe()) {
+		if (!cpu_if->vgic_sre)
+			dsb(st);
 	}

Nit:
	if ((used_lrs || !has_vhe()) && !cpu_if->vgic_sre)
		dsb(st);

I don't think that's easier to read and I'm not paying for vertical
space, so I'm going to keep it as is.

Thanks,
-Christoffer