On 2/20/2024 11:04 AM, Chao Gao wrote:
On Sun, Feb 18, 2024 at 11:47:16PM -0800, Yang Weijiang wrote:
Tweak the code a bit to facilitate resetting more xstate components in
the future, e.g., CET's xstate-managed MSRs.
No functional change intended.
Strictly speaking, there is a functional change. in the previous logic, if
either of BNDCSR or BNDREGS state is not supported (kvm_mpx_supported() will
return false), KVM won't reset either of them.
Since this gets changed, I vote
to drop 'No functional change ..'
Yes, I'll remove it since existing logic is slightly changed.
Suggested-by: Chao Gao <chao.gao@xxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
arch/x86/kvm/x86.c | 30 +++++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 10847e1cc413..5a9c07751c0e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12217,11 +12217,27 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
static_branch_dec(&kvm_has_noapic_vcpu);
}
+#define XSTATE_NEED_RESET_MASK (XFEATURE_MASK_BNDREGS | \
+ XFEATURE_MASK_BNDCSR)
+
+static bool kvm_vcpu_has_xstate(unsigned long xfeature)
kvm_vcpu_has_xstate is a misnomer because it doesn't take a vCPU.
True, I'll change it, thanks!
+{
+ switch (xfeature) {
+ case XFEATURE_MASK_BNDREGS:
+ case XFEATURE_MASK_BNDCSR:
+ return kvm_cpu_cap_has(X86_FEATURE_MPX);
+ default:
+ return false;
+ }
+}
+
void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
{
struct kvm_cpuid_entry2 *cpuid_0x1;
unsigned long old_cr0 = kvm_read_cr0(vcpu);
+ DECLARE_BITMAP(reset_mask, 64);
unsigned long new_cr0;
+ unsigned int i;
/*
* Several of the "set" flows, e.g. ->set_cr0(), read other registers
@@ -12274,7 +12290,12 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
kvm_async_pf_hash_reset(vcpu);
vcpu->arch.apf.halted = false;
- if (vcpu->arch.guest_fpu.fpstate && kvm_mpx_supported()) {
+ bitmap_from_u64(reset_mask, (kvm_caps.supported_xcr0 |
+ kvm_caps.supported_xss) &
+ XSTATE_NEED_RESET_MASK);
+
+ if (vcpu->arch.guest_fpu.fpstate &&
+ !bitmap_empty(reset_mask, XFEATURE_MAX)) {
struct fpstate *fpstate = vcpu->arch.guest_fpu.fpstate;
/*
@@ -12284,8 +12305,11 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
if (init_event)
kvm_put_guest_fpu(vcpu);
- fpstate_clear_xstate_component(fpstate, XFEATURE_BNDREGS);
- fpstate_clear_xstate_component(fpstate, XFEATURE_BNDCSR);
+ for_each_set_bit(i, reset_mask, XFEATURE_MAX) {
+ if (!kvm_vcpu_has_xstate(i))
+ continue;
The kvm_vcpu_has_xstate() check is superfluous because @i is derived from
kvm_caps.supported_xcr0/xss, which already guarantees that all unsupported
xfeatures are filtered out.
Yeah, at least currently I can skip the check for CET/MPX feaures, will remove it, thanks!
I recommend dropping this check. w/ this change,
Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>
+ fpstate_clear_xstate_component(fpstate, i);
+ }
if (init_event)
kvm_load_guest_fpu(vcpu);
--
2.43.0
