On 3/3/25 02:15, Yan Zhao wrote:
On Sat, Mar 01, 2025 at 02:34:25AM -0500, Paolo Bonzini wrote:
In some cases, the handling of quirks is split between platform-specific
code and generic code, or it is done entirely in generic code, but the
relevant bug does not trigger on some platforms; for example,
KVM_X86_QUIRK_CD_NW_CLEARED is only applicable to AMD systems. In that
case, allow unaffected vendor modules to disable handling of the quirk.
The quirk remains available in KVM_CAP_DISABLE_QUIRKS2, because that API
tells userspace that KVM *knows* that some of its past behavior was bogus
or just undesirable. In other words, it's plausible for userspace to
refuse to run if a quirk is not listed by KVM_CAP_DISABLE_QUIRKS2.
In kvm_check_has_quirk(), in addition to checking if a quirk is not
explicitly disabled by the user, also verify if the quirk applies to
the hardware.
Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
Message-ID: <20250224070832.31394-1-yan.y.zhao@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 1 +
arch/x86/kvm/x86.c | 1 +
arch/x86/kvm/x86.h | 12 +++++++-----
3 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 486fbdb4365c..75df4caea2f7 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8506,6 +8506,7 @@ __init int vmx_hardware_setup(void)
kvm_set_posted_intr_wakeup_handler(pi_wakeup_handler);
+ kvm_caps.inapplicable_quirks = KVM_X86_QUIRK_CD_NW_CLEARED;
As you mentioned, KVM_X86_QUIRK_CD_NW_CLEARED has no effect on Intel's
platforms, no matter kvm_check_has_quirk() returns true or false.
So, what's the purpose to introduce kvm_caps.inapplicable_quirks?
The purpose is to later mark IGNORE_GUEST_PAT as inapplicable, so that
the relevant code does not run on AMD. However you have a point here:
One concern is that since KVM_X86_QUIRK_CD_NW_CLEARED is not for Intel
platforms, it's unnatural for Intel's code to add it into the
kvm_caps.inapplicable_quirks.
So let's instead have kvm-amd.ko clear it from inapplicable_quirks. And
likewise kvm-intel.ko can clear IGNORE_GUEST_PAT.
Paolo
