Messages in this thread Patch in this message | | | Date | Mon, 7 Mar 2022 20:20:19 +0800 | Subject | Re: [PATCH v4 1/2] x86/arch_prctl: Fix the ARCH_REQ_XCOMP_PERM implementation | From | Hao Xiang <> |
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x86/arch_prctl: Fix the ARCH_REQ_XCOMP_PERM implementation
If WRITE_ONCE(perm->__state_perm, requested) is modified to WRITE_ONCE(perm->__state_perm, mask), When the qemu process does not request the XFEATURE_MASK_XTILE_DATA xsave state permission, there may be a gp error (kvm: kvm_set_xcr line 1091 inject gp fault with cpl 0) because __kvm_set_xcr return 1.
static int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr){ ... // xcr0 includes XFEATURE_MASK_XTILE_CFG by default. if ((xcr0 & XFEATURE_MASK_XTILE) && ((xcr0 & XFEATURE_MASK_XTILE) != XFEATURE_MASK_XTILE)) return 1; ... }
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 02b3dda..2d4363e 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1636,7 +1636,7 @@ static int __xstate_request_perm(u64 permitted, u64 requested, bool guest)
perm = guest ? &fpu->guest_perm : &fpu->perm; /* Pairs with the READ_ONCE() in xstate_get_group_perm() */ - WRITE_ONCE(perm->__state_perm, requested); + WRITE_ONCE(perm->__state_perm, mask); /* Protected by sighand lock */ perm->__state_size = ksize; perm->__user_state_size = usize; diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 494d4d3..e8704568 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -908,6 +908,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) break; case 0xd: { u64 permitted_xcr0 = supported_xcr0 & xstate_get_guest_group_perm(); + permitted_xcr0 = ((permitted_xcr0 & XFEATURES_MASK_XTILE) != XFEATURES_MASK_XTILE) + ? permitted_xcr0 + : permitted_xcr0 & ~XFEATURES_MASK_XTILE; u64 permitted_xss = supported_xss;
entry->eax &= permitted_xcr0;
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