On Mon, 01 Jul 2024 11:57:07 +0100, James Gowans jgowans@amazon.com wrote:
From: Marc Zyngier maz@kernel.org
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@vger.kernel.org Fixes: 8e01d9a396e6 ("KVM: arm64: vgic-v4: Move the GICv4 residency flow to be driven by vcpu_load/put") Reported-by: Xiang Chen chenxiang66@hisilicon.com Suggested-by: Zenghui Yu yuzenghui@huawei.com Tested-by: Xiang Chen chenxiang66@hisilicon.com Co-developed-by: Oliver Upton oliver.upton@linux.dev Signed-off-by: Marc Zyngier maz@kernel.org Acked-by: Zenghui Yu yuzenghui@huawei.com Link: https://lore.kernel.org/r/20230713070657.3873244-1-maz@kernel.org Signed-off-by: Oliver Upton oliver.upton@linux.dev
(cherry picked from commit b321c31c9b7b309dcde5e8854b741c8e6a9a05f0)
[modified to wrangle the vCPU flags directly instead of going through the flag helper macros as they have not yet been introduced. Also doing the flag wranging in the kvm_arch_vcpu_{un}blocking() hooks as the introduction of kvm_vcpu_wfi has not yet happened. See: 6109c5a6ab7f ("KVM: arm64: Move vGIC v4 handling for WFI out arch callback hook")]
Signed-off-by: James Gowans jgowans@amazon.com
Acked-by: Marc Zyngier maz@kernel.org
M.