Re: [PATCH v5 2/2] target/arm/hvf: Sync CNTV_CTL_EL0 & CNTV_CVAL_EL0

[Zenghui Yu <zenghui.yu@linux.dev>]

Hi,

On 2/23/26 9:47 PM, Lucas Kornicki wrote:
> Hi. I've found this patch to break EDK2 UEFI on MacOS 15.7
> With it applied, the vm is usually stuck on display not initialized, but
> sometimes it will init and hang on the tianocore logo.
> I've narrowed it down to
> 
> b = hvf_sysreg_write_cp(cpu, "VTimer", SYSREG_CNTV_CVAL_EL0, val);
> 
> in hvf_arch_get_registers.

It was fixed by a revert. See commit 28b0ed32b32c in master.

> 
> On a related note, I've noticed that when using accel=hvf on aarch64,
> the cpu usage is maxing out all assigned cores even if the guest is
> idle. It looks like it's constantly getting woken up from WFI. Could
> this patch be part of the solution?

This is another issue which I had also reported in [*]. It looks to me
that commit b5f8f7727177 has made the WFI handling "an immediate
re-entering in guest" which results in the high CPU utilization.

Before someone familiar with the code acknowledges it, I just reverted
b5f8f7727177 locally for power saving. ;-)

[*]
https://lore.kernel.org/qemu-devel/92a63a78-2ab8-481a-8b78-3a86fa130fe8@linux.dev

Thanks,
Zenghui