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Date: Tue, 25 Oct 2022 15:47:31 +0300 From: Maxim Levitsky <mlevitsk@...hat.com> To: kvm@...r.kernel.org Cc: Thomas Gleixner <tglx@...utronix.de>, Yang Zhong <yang.zhong@...el.com>, x86@...nel.org, Jim Mattson <jmattson@...gle.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, Wanpeng Li <wanpengli@...cent.com>, Shuah Khan <shuah@...nel.org>, Guang Zeng <guang.zeng@...el.com>, Joerg Roedel <joro@...tes.org>, Maxim Levitsky <mlevitsk@...hat.com>, linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...ux.intel.com>, Ingo Molnar <mingo@...hat.com>, linux-kselftest@...r.kernel.org, Kees Cook <keescook@...omium.org>, "H. Peter Anvin" <hpa@...or.com>, Wei Wang <wei.w.wang@...el.com>, Borislav Petkov <bp@...en8.de> Subject: [PATCH RESEND v4 13/23] KVM: x86: emulator: update the emulation mode after CR0 write Update the emulation mode when handling writes to CR0, because toggling CR0.PE switches between Real and Protected Mode, and toggling CR0.PG when EFER.LME=1 switches between Long and Protected Mode. This is likely a benign bug because there is no writeback of state, other than the RIP increment, and when toggling CR0.PE, the CPU has to execute code from a very low memory address. Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com> --- arch/x86/kvm/emulate.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 2c56d08b426065..5cc3efa0e21c17 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3290,11 +3290,25 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt) static int em_cr_write(struct x86_emulate_ctxt *ctxt) { - if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val)) + int cr_num = ctxt->modrm_reg; + int r; + + if (ctxt->ops->set_cr(ctxt, cr_num, ctxt->src.val)) return emulate_gp(ctxt, 0); /* Disable writeback. */ ctxt->dst.type = OP_NONE; + + if (cr_num == 0) { + /* + * CR0 write might have updated CR0.PE and/or CR0.PG + * which can affect the cpu's execution mode. + */ + r = emulator_recalc_and_set_mode(ctxt); + if (r != X86EMUL_CONTINUE) + return r; + } + return X86EMUL_CONTINUE; } -- 2.34.3
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