From: Alexandru Elisei <alexandru.elisei@arm.com> To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: maz@kernel.org, andre.przywara@arm.com, pbonzini@redhat.com Subject: [kvm-unit-tests RFC PATCH 02/16] arm/arm64: psci: Don't run C code without stack or vectors Date: Wed, 28 Aug 2019 14:38:17 +0100 Message-ID: <1566999511-24916-3-git-send-email-alexandru.elisei@arm.com> (raw) In-Reply-To: <1566999511-24916-1-git-send-email-alexandru.elisei@arm.com> The psci test performs a series of CPU_ON/CPU_OFF cycles for CPU 1. This is done by setting the entry point for the CPU_ON call to the physical address of the C function cpu_psci_cpu_die. The compiler is well within its rights to use the stack when generating code for cpu_psci_cpu_die. However, because no stack initialization has been done, the stack pointer is zero, as set by KVM when creating the VCPU. This causes a data abort without a change in exception level. The VBAR_EL1 register is also zero (the KVM reset value for VBAR_EL1), the MMU is off, and we end up trying to fetch instructions from address 0x200. At this point, a stage 2 instruction abort is generated which is taken to KVM. KVM interprets this as an instruction fetch from an I/O region, and injects a prefetch abort into the guest. Prefetch abort is a synchronous exception, and on guest return the VCPU PC will be set to VBAR_EL1 + 0x200, which is... 0x200. The VCPU ends up in an infinite loop causing a prefetch abort while fetching the instruction to service the said abort. cpu_psci_cpu_die is basically a wrapper over the HVC instruction, so provide an assembly implementation for the function which will serve as the entry point for CPU_ON. Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> --- arm/cstart.S | 7 +++++++ arm/cstart64.S | 7 +++++++ arm/psci.c | 5 +++-- 3 files changed, 17 insertions(+), 2 deletions(-) diff --git a/arm/cstart.S b/arm/cstart.S index 114726feab82..5d4fe4b1570b 100644 --- a/arm/cstart.S +++ b/arm/cstart.S @@ -7,6 +7,7 @@ */ #define __ASSEMBLY__ #include <auxinfo.h> +#include <linux/psci.h> #include <asm/thread_info.h> #include <asm/asm-offsets.h> #include <asm/ptrace.h> @@ -138,6 +139,12 @@ secondary_entry: blx r0 b do_idle +.global asm_cpu_psci_cpu_die +asm_cpu_psci_cpu_die: + ldr r0, =PSCI_0_2_FN_CPU_OFF + hvc #0 + b halt + .globl halt halt: 1: wfi diff --git a/arm/cstart64.S b/arm/cstart64.S index b0e8baa1a23a..20f832fd57f7 100644 --- a/arm/cstart64.S +++ b/arm/cstart64.S @@ -7,6 +7,7 @@ */ #define __ASSEMBLY__ #include <auxinfo.h> +#include <linux/psci.h> #include <asm/asm-offsets.h> #include <asm/ptrace.h> #include <asm/processor.h> @@ -128,6 +129,12 @@ secondary_entry: blr x0 b do_idle +.globl asm_cpu_psci_cpu_die +asm_cpu_psci_cpu_die: + ldr x0, =PSCI_0_2_FN_CPU_OFF + hvc #0 + b halt + .globl halt halt: 1: wfi diff --git a/arm/psci.c b/arm/psci.c index 5cb4d5c7c233..0440c4cdbc59 100644 --- a/arm/psci.c +++ b/arm/psci.c @@ -72,6 +72,7 @@ static int cpu_on_ret[NR_CPUS]; static cpumask_t cpu_on_ready, cpu_on_done; static volatile int cpu_on_start; +extern void asm_cpu_psci_cpu_die(void); static void cpu_on_secondary_entry(void) { int cpu = smp_processor_id(); @@ -79,7 +80,7 @@ static void cpu_on_secondary_entry(void) cpumask_set_cpu(cpu, &cpu_on_ready); while (!cpu_on_start) cpu_relax(); - cpu_on_ret[cpu] = psci_cpu_on(cpus[1], __pa(cpu_psci_cpu_die)); + cpu_on_ret[cpu] = psci_cpu_on(cpus[1], __pa(asm_cpu_psci_cpu_die)); cpumask_set_cpu(cpu, &cpu_on_done); } @@ -104,7 +105,7 @@ static bool psci_cpu_on_test(void) cpu_on_start = 1; smp_mb(); - cpu_on_ret[0] = psci_cpu_on(cpus[1], __pa(cpu_psci_cpu_die)); + cpu_on_ret[0] = psci_cpu_on(cpus[1], __pa(asm_cpu_psci_cpu_die)); cpumask_set_cpu(0, &cpu_on_done); while (!cpumask_full(&cpu_on_done)) -- 2.7.4 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
next prev parent reply index Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-08-28 13:38 [kvm-unit-tests RFC PATCH 00/16] arm64: Run at EL2 Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 01/16] arm: selftest.c: Remove redundant check for Exception Level Alexandru Elisei 2019-08-28 14:32 ` Andrew Jones 2019-08-28 15:39 ` Alexandru Elisei 2019-08-28 13:38 ` Alexandru Elisei [this message] 2019-08-28 14:45 ` [kvm-unit-tests RFC PATCH 02/16] arm/arm64: psci: Don't run C code without stack or vectors Andrew Jones 2019-08-28 15:14 ` Alexandru Elisei 2019-09-02 14:55 ` Alexandru Elisei 2019-09-03 6:37 ` Andrew Jones 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 03/16] lib: arm/arm64: Add missing include for alloc_page.h in pgtable.h Alexandru Elisei 2019-08-28 14:47 ` Andrew Jones 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 04/16] arm/arm64: selftest: Add prefetch abort test Alexandru Elisei 2019-08-28 14:09 ` Mark Rutland 2019-08-29 8:18 ` Alexandru Elisei 2019-08-29 10:19 ` Mark Rutland 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 05/16] arm64: timer: Write to ICENABLER to disable timer IRQ Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 06/16] arm64: timer: EOIR the interrupt after masking the timer Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 07/16] arm64: timer: Test behavior when timer disabled or masked Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 08/16] lib: arm/arm64: Refuse to disable the MMU with non-identity stack pointer Alexandru Elisei 2019-08-28 14:55 ` Andrew Jones 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 09/16] lib: arm/arm64: Invalidate TLB before enabling MMU Alexandru Elisei 2019-08-28 14:59 ` Andrew Jones 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 10/16] lib: Add UL and ULL definitions to linux/const.h Alexandru Elisei 2019-08-28 15:10 ` Andrew Jones 2019-08-28 15:46 ` Alexandru Elisei 2019-08-28 16:19 ` Andrew Jones 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 11/16] lib: arm64: Run existing tests at EL2 Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 12/16] arm64: timer: Add test for EL2 timers Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 13/16] arm64: selftest: Add basic test for EL2 Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 14/16] lib: arm64: Add support for disabling and re-enabling VHE Alexandru Elisei 2019-08-28 14:19 ` Mark Rutland 2019-08-29 8:36 ` Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 15/16] arm64: selftest: Expand EL2 test to disable and re-enable VHE Alexandru Elisei 2019-08-28 13:38 ` [kvm-unit-tests RFC PATCH 16/16] arm64: timer: Run tests with VHE disabled Alexandru Elisei
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