[PATCH 2/2] qemu: Generate command line for tb-cache feature

[Michal Prívozník]

On 11/4/21 6:25 PM, Daniel P. Berrangé wrote:
> On Thu, Nov 04, 2021 at 01:22:53PM +0100, Michal Privoznik wrote:
>> Alright, here's the deal: to enable tb-cache one has to use
>> '-accel tcg,tb-size=' which then conflicts with '-machine
>> accel=tcg'. But sure, we can use the old -accel in this specific
>> case. But because of how the tb-size argument is defined in QEMU
>> there's no way for us to have a capability check. The feature was
>> introduced in QEMU commit of v5.0.0-rc0~175^2~62 and is tied to
>> TCG only. Therefore, I think we can live without capability
>> check. Worst case scenario, QEMU fails to start.
>>
>> Resolves: https://gitlab.com/libvirt/libvirt/-/issues/229
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>>  src/qemu/qemu_command.c                       | 14 ++++++-
>>  ...efault-cpu-tcg-features.x86_64-latest.args | 40 +++++++++++++++++++
>>  tests/qemuxml2argvtest.c                      |  1 +
>>  3 files changed, 54 insertions(+), 1 deletion(-)
>>  create mode 100644 tests/qemuxml2argvdata/x86_64-default-cpu-tcg-features.x86_64-latest.args
>>


> IOW, long term we want to be using -accel exclusively.
> 
> Given our minimum QEMU 2.11.0, we can in fact use -accel
> exclusively already AFAICT.
> 
> That would simplify this patch so that we're not supporting
> distinct syntax with tb_cache.

Ah, I don't know why I thought the opposite. Let me post v2.

Michal