~myrslint <myrsl...@git.sr.ht> writes: > From: myrslint <qemu.haziness...@passinbox.com> > > Thanks to Alex Bennée <alex.ben...@linaro.org> for the kind code review > and helpful guidance.
This doesn't belong in the commit message, you can add it bellow the --- if you want to track the changes while iterating a patch: https://qemu.readthedocs.io/en/master/devel/submitting-a-patch.html#id21 > This is a second attempt at addressing this issue: > https://gitlab.com/qemu-project/qemu/-/issues/2943 This should be a trailer: Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2943 bellow your signed-of-by. > Most Intel CPUs in current use have self-snoop. The few added lines of > code also check for availability of the quirk disablement option so if > some CPU does not have this feature no change of behavior will occur. > > Signed-off-by: Myrsky Lintu <qemu.haziness...@passinbox.com> > --- > Hopefully, I have improved the patch based on kindly provided code > review. > > The only point of divergence is that per > > https://www.kernel.org/doc/html/latest/virt/kvm/api.html > > this is a VM capability (section 7), not a VCPU one, so a call is made > to kvm_vm_enable_cap() rather than kvm_vcpu_enable_cap(). > > target/i386/kvm/kvm.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c > index 369626f8c8..124818bf94 100644 > --- a/target/i386/kvm/kvm.c > +++ b/target/i386/kvm/kvm.c > @@ -16,6 +16,7 @@ > #include "qapi/qapi-events-run-state.h" > #include "qapi/error.h" > #include "qapi/visitor.h" > +#include <asm-x86/kvm.h> > #include <math.h> > #include <sys/ioctl.h> > #include <sys/utsname.h> > @@ -3367,6 +3368,24 @@ int kvm_arch_init(MachineState *ms, KVMState *s) > } > } > > +/* if kernel version does not have it there is no point compiling this in */ > +#ifdef KVM_X86_QUIRK_IGNORE_GUEST_PAT > + /* rationale: most x86 cpus in current use have self-snoop so honoring > + * guest pat is preferrable. as well, the bochs video driver bug which > + * motivated making this a default enabled quirk in kvm was fixed long > ago > + * */ > + /* check if disabling this quirk is feasible and allowed */ > + ret = kvm_check_extension(s, KVM_CAP_DISABLE_QUIRKS2); > + if (ret & KVM_X86_QUIRK_IGNORE_GUEST_PAT) { > + ret = kvm_vm_enable_cap(s, KVM_CAP_DISABLE_QUIRKS2, 0, \ > + KVM_X86_QUIRK_IGNORE_GUEST_PAT); > + if (ret < 0) { > + error_report("KVM_X86_QUIRK_IGNORE_GUEST_PAT available and " > + "modifiable but we failed to disable it\n"); > + } > + } > +#endif This looks good now, I'll leave it to the x86 maintainers to decide on the automatic enabling of this feature. > + > return 0; > } -- Alex Bennée Virtualisation Tech Lead @ Linaro
