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Tsirkin" , Alexander Graf , kvm@vger.kernel.org, Peter Maydell , Paolo Bonzini , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , =?utf-8?q?Alex?= =?utf-8?q?_Benn=C3=A9e?= Subject: [RFC PATCH 11/11] kvm/arm: implement WFx traps for KVM Date: Tue, 17 Jun 2025 17:33:51 +0100 Message-ID: <20250617163351.2640572-12-alex.bennee@linaro.org> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250617163351.2640572-1-alex.bennee@linaro.org> References: <20250617163351.2640572-1-alex.bennee@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::433; envelope-from=alex.bennee@linaro.org; helo=mail-wr1-x433.google.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org This allows the vCPU guest core to go to sleep on a WFx instruction. Signed-off-by: Alex Bennée --- target/arm/kvm.c | 28 ++++++++++++++++++++++++++++ target/arm/trace-events | 1 + 2 files changed, 29 insertions(+) diff --git a/target/arm/kvm.c b/target/arm/kvm.c index 1280e2c1e8..63ba8573a2 100644 --- a/target/arm/kvm.c +++ b/target/arm/kvm.c @@ -1544,6 +1544,32 @@ static int kvm_arm_handle_hypercall(ARMCPU *cpu, return 0; } +/* + * It would be perfectly fine to immediately return from any WFE/WFI + * trap however that would mean we spend a lot of time bouncing + * between the hypervisor and QEMU when things are idle. + */ + +static const char * wfx_insn[] = { + "WFI", + "WFE", + "WFIT", + "WFET" +}; + +static int kvm_arm_handle_wfx(CPUState *cs, int esr_iss) +{ + int ti = extract32(esr_iss, 0, 2); + ARMCPU *cpu = ARM_CPU(cs); + CPUARMState *env = &cpu->env; + + trace_kvm_wfx_trap(cs->cpu_index, wfx_insn[ti], env->pc); + + /* stop the CPU, return to the top of the loop */ + cs->stop = true; + return EXCP_YIELD; +} + /** * kvm_arm_handle_hard_trap: * @cpu: ARMCPU @@ -1582,6 +1608,8 @@ static int kvm_arm_handle_hard_trap(ARMCPU *cpu, case EC_AA64_HVC: case EC_AA64_SMC: return kvm_arm_handle_hypercall(cpu, esr_ec); + case EC_WFX_TRAP: + return kvm_arm_handle_wfx(cs, esr_iss); default: qemu_log_mask(LOG_UNIMP, "%s: unhandled EC: %x/%x/%x/%d\n", __func__, esr_ec, esr_iss, esr_iss2, esr_il); diff --git a/target/arm/trace-events b/target/arm/trace-events index 10cdba92a3..bb02da12ab 100644 --- a/target/arm/trace-events +++ b/target/arm/trace-events @@ -16,3 +16,4 @@ kvm_arm_fixup_msi_route(uint64_t iova, uint64_t gpa) "MSI iova = 0x%"PRIx64" is kvm_sysreg_read(const char *name, uint64_t val) "%s => 0x%" PRIx64 kvm_sysreg_write(const char *name, uint64_t val) "%s <= 0x%" PRIx64 kvm_hypercall(int ec, uint64_t arg0) "%d: %"PRIx64 +kvm_wfx_trap(int vcpu, const char *insn, uint64_t vaddr) "%d: %s @ 0x%" PRIx64