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Thu, 30 Jan 2020 13:26:35 +0000 From: Marc Zyngier To: Paolo Bonzini Subject: [PATCH 23/23] KVM: arm64: Treat emulated TVAL TimerValue as a signed 32-bit integer Date: Thu, 30 Jan 2020 13:25:58 +0000 Message-Id: <20200130132558.10201-24-maz@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200130132558.10201-1-maz@kernel.org> References: <20200130132558.10201-1-maz@kernel.org> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: pbonzini@redhat.com, alexandru.elisei@arm.com, drjones@redhat.com, andrew.murray@arm.com, beata.michalska@linaro.org, christoffer.dall@arm.com, eric.auger@redhat.com, gshan@redhat.com, wanghaibin.wang@huawei.com, james.morse@arm.com, broonie@kernel.org, mark.rutland@arm.com, rmk+kernel@armlinux.org.uk, shannon.zhao@linux.alibaba.com, steven.price@arm.com, will@kernel.org, yuehaibing@huawei.com, yuzenghui@huawei.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200130_052920_158275_E94536FB X-CRM114-Status: GOOD ( 13.75 ) X-Spam-Score: -5.2 (-----) X-Spam-Report: SpamAssassin version 3.4.3 on bombadil.infradead.org summary: Content analysis details: (-5.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [198.145.29.99 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Gavin Shan , Beata Michalska , kvm@vger.kernel.org, Will Deacon , kvmarm@lists.cs.columbia.edu, YueHaibing , Steven Price , Zenghui Yu , Haibin Wang , Julien Thierry , Andrew Jones , Suzuki K Poulose , Shannon Zhao , Eric Auger , Russell King , Mark Brown , Alexandru Elisei , linux-arm-kernel@lists.infradead.org, Christoffer Dall , James Morse , Andrew Murray Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: Alexandru Elisei According to the ARM ARM, registers CNT{P,V}_TVAL_EL0 have bits [63:32] RES0 [1]. When reading the register, the value is truncated to the least significant 32 bits [2], and on writes, TimerValue is treated as a signed 32-bit integer [1, 2]. When the guest behaves correctly and writes 32-bit values, treating TVAL as an unsigned 64 bit register works as expected. However, things start to break down when the guest writes larger values, because (u64)0x1_ffff_ffff = 8589934591. but (s32)0x1_ffff_ffff = -1, and the former will cause the timer interrupt to be asserted in the future, but the latter will cause it to be asserted now. Let's treat TVAL as a signed 32-bit register on writes, to match the behaviour described in the architecture, and the behaviour experimentally exhibited by the virtual timer on a non-vhe host. [1] Arm DDI 0487E.a, section D13.8.18 [2] Arm DDI 0487E.a, section D11.2.4 Signed-off-by: Alexandru Elisei [maz: replaced the read-side mask with lower_32_bits] Signed-off-by: Marc Zyngier Fixes: 8fa761624871 ("KVM: arm/arm64: arch_timer: Fix CNTP_TVAL calculation") Link: https://lore.kernel.org/r/20200127103652.2326-1-alexandru.elisei@arm.com --- virt/kvm/arm/arch_timer.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index f182b2380345..c6c2a9dde00c 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -805,6 +805,7 @@ static u64 kvm_arm_timer_read(struct kvm_vcpu *vcpu, switch (treg) { case TIMER_REG_TVAL: val = timer->cnt_cval - kvm_phys_timer_read() + timer->cntvoff; + val &= lower_32_bits(val); break; case TIMER_REG_CTL: @@ -850,7 +851,7 @@ static void kvm_arm_timer_write(struct kvm_vcpu *vcpu, { switch (treg) { case TIMER_REG_TVAL: - timer->cnt_cval = kvm_phys_timer_read() - timer->cntvoff + val; + timer->cnt_cval = kvm_phys_timer_read() - timer->cntvoff + (s32)val; break; case TIMER_REG_CTL: