On Wed, Aug 21, 2019 at 07:54:17PM +0800, owen...@ucloud.cn wrote: > It is CentOS 6.3 with kernel version 2.6.32-279. Actually all CentOS 6 > releases have this issue.
We stopped supporting CentOS 6 in July 2016 (2 years after CentOS 7 was released). Be aware that even if we work around that specific bug, there are no guarantees that QEMU will still build on a CentOS 6 host in the future. That said, I probably wouldn't reject a patch that works around that CentOS 6 bug, if it's conditional on kvm_enabled() and has a comment explaining why the workaround exists. > > > > owen...@ucloud.cn > > From: Eduardo Habkost > Date: 2019-08-21 19:19 > To: owen...@ucloud.cn > CC: qemu-devel > Subject: Re: Re: [Qemu-devel] [PATCH] Revert "i386: correct > cpu_x86_cpuid(0xd)" > On Wed, Aug 21, 2019 at 11:04:46AM +0800, owen...@ucloud.cn wrote: > > Thanks for you reply, we have some hosts running with legacy kernel, > > difficult to upgrade, and i want to run the latest qemu. > > Does QEMU support running with legacy kernel(kvm) in design? > > For KVM, QEMU requires Linux 4.5 or newer. See "System > requirements" / "KVM kernel module" section on qemu-doc. We also > aim to support the latest version of Linux distributions with > long term support (e.g. RHEL, Debian, Ubuntu LTS, SLES). > > Do you have more details on the kernel you are using? Is it > built and distributed by a third party? > > > > > > > > > > owen...@ucloud.cn > > > > From: Eduardo Habkost > > Date: 2019-08-21 05:23 > > To: Bingsong Si > > CC: qemu-devel > > Subject: Re: [Qemu-devel] [PATCH] Revert "i386: correct cpu_x86_cpuid(0xd)" > > On Mon, Aug 19, 2019 at 06:09:24PM +0800, Bingsong Si wrote: > > > This reverts commit de2e68c902f7b6e438b0fa3cfedd74a06a20704f. > > > > > > Initial value of env->xcr0 == 0, then CPUID(EAX=0xd,ECX=0).EBX == 0, > > > after kvm > > > upstream commit 412a3c41, It is ok. > > > On host before commit 412a3c41, some legacy guest, i.e. CentOS 6, get > > > xstate_size == 0, will crash the guest. > > > > > > Signed-off-by: Bingsong Si <owen...@ucloud.cn> > > > > cpu_x86_cpuid() is also used by TCG, and needs to return the > > correct data depending on xcr0. If you want to work around a KVM > > bug by ignoring xcr0, it needs to be conditional on > > kvm_enabled(). > > > > But even if we you make this conditional on kvm_enabled(), I > > don't understand why QEMU would need a workaround for a KVM bug > > that was fixed more than 4 years ago. > > > > > --- > > > target/i386/cpu.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > > > index ff65e11008..69562e21ed 100644 > > > --- a/target/i386/cpu.c > > > +++ b/target/i386/cpu.c > > > @@ -4416,7 +4416,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t > > > index, uint32_t count, > > > *ecx = xsave_area_size(x86_cpu_xsave_components(cpu)); > > > *eax = env->features[FEAT_XSAVE_COMP_LO]; > > > *edx = env->features[FEAT_XSAVE_COMP_HI]; > > > - *ebx = xsave_area_size(env->xcr0); > > > + *ebx = *ecx; > > > } else if (count == 1) { > > > *eax = env->features[FEAT_XSAVE]; > > > } else if (count < ARRAY_SIZE(x86_ext_save_areas)) { > > > -- > > > 2.22.0 > > > > > > > > > > -- > > Eduardo > > -- > Eduardo -- Eduardo