6.12-stable review patch. If anyone has any objections, please let me know.
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From: Yosry Ahmed yosry.ahmed@linux.dev
commit 5674a76db0213f9db1e4d08e847ff649b46889c0 upstream.
When emulating L2 instructions, svm_check_intercept() checks whether a write to CR0 should trigger a synthesized #VMEXIT with SVM_EXIT_CR0_SEL_WRITE. For MOV-to-CR0, SVM_EXIT_CR0_SEL_WRITE is only triggered if any bit other than CR0.MP and CR0.TS is updated. However, according to the APM (24593—Rev. 3.42—March 2024, Table 15-7):
The LMSW instruction treats the selective CR0-write intercept as a non-selective intercept (i.e., it intercepts regardless of the value being written).
Skip checking the changed bits for x86_intercept_lmsw and always inject SVM_EXIT_CR0_SEL_WRITE.
Fixes: cfec82cb7d31 ("KVM: SVM: Add intercept check for emulated cr accesses") Cc: stable@vger.kernel.org Reported-by: Matteo Rizzo matteorizzo@google.com Signed-off-by: Yosry Ahmed yosry.ahmed@linux.dev Link: https://patch.msgid.link/20251024192918.3191141-3-yosry.ahmed@linux.dev Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm/svm.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)
--- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4675,20 +4675,20 @@ static int svm_check_intercept(struct kv if (info->intercept == x86_intercept_clts) break;
- cr0 = vcpu->arch.cr0 & ~SVM_CR0_SELECTIVE_MASK; - val = info->src_val & ~SVM_CR0_SELECTIVE_MASK; - + /* LMSW always triggers INTERCEPT_SELECTIVE_CR0 */ if (info->intercept == x86_intercept_lmsw) { - cr0 &= 0xfUL; - val &= 0xfUL; - /* lmsw can't clear PE - catch this here */ - if (cr0 & X86_CR0_PE) - val |= X86_CR0_PE; + icpt_info.exit_code = SVM_EXIT_CR0_SEL_WRITE; + break; }
+ /* + * MOV-to-CR0 only triggers INTERCEPT_SELECTIVE_CR0 if any bit + * other than SVM_CR0_SELECTIVE_MASK is changed. + */ + cr0 = vcpu->arch.cr0 & ~SVM_CR0_SELECTIVE_MASK; + val = info->src_val & ~SVM_CR0_SELECTIVE_MASK; if (cr0 ^ val) icpt_info.exit_code = SVM_EXIT_CR0_SEL_WRITE; - break; } case SVM_EXIT_READ_DR0: