[Expired for QEMU because there has been no activity for 60 days.]
** Changed in: qemu
Status: Incomplete => Expired
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https://bugs.launchpad.net/bugs/1904317
Title:
cpu feature selection is not affected to guest 's cpuid with whpx
Status in QEMU:
Expired
Bug description:
On windows with -accel whpx, "-cpu" is ignored without any messages.
Guest recognizes features as same as host's.
Confirmed on v5.2.0-rc1.
I suggest qemu may do,
- Warn with incompatible -cpu options were given.
- Enhance cpuid handling.
Background:
I was investigated mmio and block copy issue in Linux kernel.
I met a problem that Linux went ill for touching mmio with whpx. (not with
tcg)
I suspect erms(enhanced rep movs) might trigger.
I tried to mask erms on qemu with -feature,erms, but it was ineffective.
At last, I disabled erms manually, to tweak whpx-all.c to mask erms in
cpuid.
FYI, qemu with whpx from/to mmio, "rep movsb" does byte access regardless of
erms.
Linux kernel tends to choose not "rep movsq" but "rep movsb" with erms.
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