On 09/15 05:51, Dr. David Alan Gilbert wrote: > * Vitaly Kuznetsov (vkuznets@xxxxxxxxxx) wrote: > > With QEMU and newer AMD CPUs (namely: Epyc 'Rome') the current limit for Could you elaborate on this limit? On Rome, I counted ~35 CPUID functions which include Fn0000_xxxx, Fn4000_xxxx and Fn8000_xxxx. > > KVM_MAX_CPUID_ENTRIES(80) is reported to be hit. Last time it was raised > > from '40' in 2010. We can, of course, just bump it a little bit to fix > > the immediate issue but the report made me wonder why we need to pre- > > allocate vcpu->arch.cpuid_entries array instead of sizing it dynamically. > > This RFC is intended to feed my curiosity. > > > > Very mildly tested with selftests/kvm-unit-tests and nothing seems to > > break. I also don't have access to the system where the original issue > > was reported but chances we're fixing it are very good IMO as just the > > second patch alone was reported to be sufficient. > > > > Reported-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx> > > Oh nice, I was just going to bump the magic number :-) > > Anyway, this seems to work for me, so: > > Tested-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx> > I tested on two platforms and the patches worked fine. So no objection on the design. Tested-by: Wei Huang <wei.huang2@xxxxxxx> > > Vitaly Kuznetsov (2): > > KVM: x86: allocate vcpu->arch.cpuid_entries dynamically > > KVM: x86: bump KVM_MAX_CPUID_ENTRIES > > > > arch/x86/include/asm/kvm_host.h | 4 +-- > > arch/x86/kvm/cpuid.c | 55 ++++++++++++++++++++++++--------- > > arch/x86/kvm/x86.c | 1 + > > 3 files changed, 43 insertions(+), 17 deletions(-) > > > > -- > > 2.25.4 > > > -- > Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK >
