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[91.199.104.161]) by mx.google.com with ESMTPS id s13si1505788wru.417.2019.08.09.09.01.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 09 Aug 2019 09:01:45 -0700 (PDT) Received-SPF: pass (google.com: domain of alazar@bitdefender.com designates 91.199.104.161 as permitted sender) client-ip=91.199.104.161; Authentication-Results: mx.google.com; spf=pass (google.com: domain of alazar@bitdefender.com designates 91.199.104.161 as permitted sender) smtp.mailfrom=alazar@bitdefender.com Received: from smtp.bitdefender.com (smtp02.buh.bitdefender.net [10.17.80.76]) by mx01.bbu.dsd.mx.bitdefender.com (Postfix) with ESMTPS id E0CC5305D36B; Fri, 9 Aug 2019 19:01:44 +0300 (EEST) Received: from localhost.localdomain (unknown [89.136.169.210]) by smtp.bitdefender.com (Postfix) with ESMTPSA id 97C8A305B7A1; Fri, 9 Aug 2019 19:01:44 +0300 (EEST) From: =?UTF-8?q?Adalbert=20Laz=C4=83r?= To: kvm@vger.kernel.org Cc: linux-mm@kvack.org, virtualization@lists.linux-foundation.org, Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Konrad Rzeszutek Wilk , Tamas K Lengyel , Mathieu Tarral , =?UTF-8?q?Samuel=20Laur=C3=A9n?= , Patrick Colp , Jan Kiszka , Stefan Hajnoczi , Weijiang Yang , Zhang@kvack.org, Yu C , =?UTF-8?q?Mihai=20Don=C8=9Bu?= , =?UTF-8?q?Adalbert=20Laz=C4=83r?= Subject: [RFC PATCH v6 92/92] kvm: x86: fallback to the single-step on multipage CMPXCHG emulation Date: Fri, 9 Aug 2019 19:00:47 +0300 Message-Id: <20190809160047.8319-93-alazar@bitdefender.com> In-Reply-To: <20190809160047.8319-1-alazar@bitdefender.com> References: <20190809160047.8319-1-alazar@bitdefender.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Mihai Donțu There are cases where we need to emulate a CMPXCHG that touches two pages (4 in one and another 4 in the next, for example). Because it is not easy to map two pages in the kernel so that we can directly execute the exchange instruction, we fallback to single-stepping. Luckly, this is an uncommon occurrence making the overhead of the single-step mechanism acceptable. Signed-off-by: Mihai Donțu Signed-off-by: Adalbert Lazăr --- arch/x86/kvm/x86.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0e904782d303..e283b074db26 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5671,6 +5671,12 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, #define CMPXCHG_MAX_BYTES 8 #endif + gpa = kvm_mmu_gva_to_gpa_write(vcpu, addr, NULL); + + if (gpa == UNMAPPED_GVA || + (gpa & PAGE_MASK) == APIC_DEFAULT_PHYS_BASE) + goto emul_write; + /* guests cmpxchg{8,16}b have to be emulated atomically */ if (bytes > CMPXCHG_MAX_BYTES || (bytes & (bytes - 1))) goto emul_write; @@ -5678,12 +5684,6 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, if (bytes == 16 && !system_has_cmpxchg_double()) goto emul_write; - gpa = kvm_mmu_gva_to_gpa_write(vcpu, addr, NULL); - - if (gpa == UNMAPPED_GVA || - (gpa & PAGE_MASK) == APIC_DEFAULT_PHYS_BASE) - goto emul_write; - if (((gpa + bytes - 1) & PAGE_MASK) != (gpa & PAGE_MASK)) goto emul_write; @@ -5772,6 +5772,9 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, return X86EMUL_CONTINUE; emul_write: + if (kvmi_tracked_gfn(vcpu, gpa >> PAGE_SHIFT)) + return X86EMUL_UNHANDLEABLE; + printk_once(KERN_WARNING "kvm: emulating exchange as write\n"); return emulator_write_emulated(ctxt, addr, new, bytes, exception);