Be a good citizen and don't allow any of the supported MPX xfeatures[1]
to be set if they can't all be set. That way userspace or a guest
doesn't fail if it attempts to set them in XCR0.
[1] CPUID.(EAX=0DH,ECX=0):EAX.BNDREGS[bit-3]
CPUID.(EAX=0DH,ECX=0):EAX.BNDCSR[bit-4]
Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx>
Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
---
arch/x86/kvm/cpuid.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e1165c196970..b2e7407cd114 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -60,9 +60,22 @@ u32 xstate_required_size(u64 xstate_bv, bool compacted)
return ret;
}
+static u64 sanitize_xcr0(u64 xcr0)
+{
+ u64 mask;
+
+ mask = XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR;
+ if ((xcr0 & mask) != mask)
+ xcr0 &= ~mask;
+
+ return xcr0;
+}
+
u64 kvm_permitted_xcr0(void)
{
- return kvm_caps.supported_xcr0 & xstate_get_guest_group_perm();
+ u64 permitted_xcr0 = kvm_caps.supported_xcr0 & xstate_get_guest_group_perm();
+
+ return sanitize_xcr0(permitted_xcr0);
}
/*
--
2.39.2.637.g21b0678d19-goog
