From eed05744322da07dd7e419432dcedf3c2e017179 Mon Sep 17 00:00:00 2001 From: Dongli Zhang Date: Wed, 2 Mar 2022 08:40:32 -0800 Subject: xen: delay xen_hvm_init_time_ops() if kdump is boot on vcpu>=32 The sched_clock() can be used very early since commit 857baa87b642 ("sched/clock: Enable sched clock early"). In addition, with commit 38669ba205d1 ("x86/xen/time: Output xen sched_clock time from 0"), kdump kernel in Xen HVM guest may panic at very early stage when accessing &__this_cpu_read(xen_vcpu)->time as in below: setup_arch() -> init_hypervisor_platform() -> x86_init.hyper.init_platform = xen_hvm_guest_init() -> xen_hvm_init_time_ops() -> xen_clocksource_read() -> src = &__this_cpu_read(xen_vcpu)->time; This is because Xen HVM supports at most MAX_VIRT_CPUS=32 'vcpu_info' embedded inside 'shared_info' during early stage until xen_vcpu_setup() is used to allocate/relocate 'vcpu_info' for boot cpu at arbitrary address. However, when Xen HVM guest panic on vcpu >= 32, since xen_vcpu_info_reset(0) would set per_cpu(xen_vcpu, cpu) = NULL when vcpu >= 32, xen_clocksource_read() on vcpu >= 32 would panic. This patch calls xen_hvm_init_time_ops() again later in xen_hvm_smp_prepare_boot_cpu() after the 'vcpu_info' for boot vcpu is registered when the boot vcpu is >= 32. This issue can be reproduced on purpose via below command at the guest side when kdump/kexec is enabled: "taskset -c 33 echo c > /proc/sysrq-trigger" The bugfix for PVM is not implemented due to the lack of testing environment. [boris: xen_hvm_init_time_ops() returns on errors instead of jumping to end] Cc: Joe Jin Signed-off-by: Dongli Zhang Reviewed-by: Boris Ostrovsky Link: https://lore.kernel.org/r/20220302164032.14569-3-dongli.zhang@oracle.com Signed-off-by: Boris Ostrovsky --- arch/x86/xen/smp_hvm.c | 6 ++++++ arch/x86/xen/time.c | 24 +++++++++++++++++++++++- 2 files changed, 29 insertions(+), 1 deletion(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/smp_hvm.c b/arch/x86/xen/smp_hvm.c index 6ff3c887e0b9..b70afdff419c 100644 --- a/arch/x86/xen/smp_hvm.c +++ b/arch/x86/xen/smp_hvm.c @@ -19,6 +19,12 @@ static void __init xen_hvm_smp_prepare_boot_cpu(void) */ xen_vcpu_setup(0); + /* + * Called again in case the kernel boots on vcpu >= MAX_VIRT_CPUS. + * Refer to comments in xen_hvm_init_time_ops(). + */ + xen_hvm_init_time_ops(); + /* * The alternative logic (which patches the unlock/lock) runs before * the smp bootup up code is activated. Hence we need to set this up diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index d9c945ee1100..9ef0a5cca96e 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -558,6 +558,11 @@ static void xen_hvm_setup_cpu_clockevents(void) void __init xen_hvm_init_time_ops(void) { + static bool hvm_time_initialized; + + if (hvm_time_initialized) + return; + /* * vector callback is needed otherwise we cannot receive interrupts * on cpu > 0 and at this point we don't know how many cpus are @@ -567,7 +572,22 @@ void __init xen_hvm_init_time_ops(void) return; if (!xen_feature(XENFEAT_hvm_safe_pvclock)) { - pr_info("Xen doesn't support pvclock on HVM, disable pv timer"); + pr_info_once("Xen doesn't support pvclock on HVM, disable pv timer"); + return; + } + + /* + * Only MAX_VIRT_CPUS 'vcpu_info' are embedded inside 'shared_info'. + * The __this_cpu_read(xen_vcpu) is still NULL when Xen HVM guest + * boots on vcpu >= MAX_VIRT_CPUS (e.g., kexec), To access + * __this_cpu_read(xen_vcpu) via xen_clocksource_read() will panic. + * + * The xen_hvm_init_time_ops() should be called again later after + * __this_cpu_read(xen_vcpu) is available. + */ + if (!__this_cpu_read(xen_vcpu)) { + pr_info("Delay xen_init_time_common() as kernel is running on vcpu=%d\n", + xen_vcpu_nr(0)); return; } @@ -577,6 +597,8 @@ void __init xen_hvm_init_time_ops(void) x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents; x86_platform.set_wallclock = xen_set_wallclock; + + hvm_time_initialized = true; } #endif -- cgit v1.2.1 From b359b3a0296a8a9c853c7ee98f9728942d7f0f4e Mon Sep 17 00:00:00 2001 From: Jiapeng Chong Date: Mon, 7 Mar 2022 14:25:54 +0800 Subject: x86/xen: Fix kerneldoc warning Fix the following W=1 kernel warnings: arch/x86/xen/setup.c:725: warning: expecting prototype for machine_specific_memory_setup(). Prototype was for xen_memory_setup() instead. Reported-by: Abaci Robot Signed-off-by: Jiapeng Chong Reviewed-by: Boris Ostrovsky Link: https://lore.kernel.org/r/20220307062554.8334-1-jiapeng.chong@linux.alibaba.com Signed-off-by: Boris Ostrovsky --- arch/x86/xen/setup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index af216feb63d9..81aa46f770c5 100644 --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -719,7 +719,7 @@ static void __init xen_reserve_xen_mfnlist(void) } /** - * machine_specific_memory_setup - Hook for machine specific memory setup. + * xen_memory_setup - Hook for machine specific memory setup. **/ char * __init xen_memory_setup(void) { -- cgit v1.2.1 From 309b517276f21dc7e6315c6637792f8bbfdf7ec4 Mon Sep 17 00:00:00 2001 From: jianchunfu Date: Mon, 14 Mar 2022 15:05:14 +0800 Subject: arch:x86:xen: Remove unnecessary assignment in xen_apic_read() In the function xen_apic_read(), the initialized value of 'ret' is unused because it will be assigned by the function HYPERVISOR_platform_op(), thus remove it. Signed-off-by: jianchunfu Link: https://lore.kernel.org/r/20220314070514.2602-1-jianchunfu@cmss.chinamobile.com Reviewed-by: Boris Ostrovsky Signed-off-by: Boris Ostrovsky --- arch/x86/xen/apic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c index 0d46cc283cf5..62d34b6611c5 100644 --- a/arch/x86/xen/apic.c +++ b/arch/x86/xen/apic.c @@ -51,7 +51,7 @@ static u32 xen_apic_read(u32 reg) .interface_version = XENPF_INTERFACE_VERSION, .u.pcpu_info.xen_cpuid = 0, }; - int ret = 0; + int ret; /* Shouldn't need this as APIC is turned off for PV, and we only * get called on the bootup processor. But just in case. */ -- cgit v1.2.1 From de2ae403b4c0e79a3410e63bc448542fbb9f9bfc Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Fri, 25 Mar 2022 15:20:02 +0100 Subject: xen: fix is_xen_pmu() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit is_xen_pmu() is taking the cpu number as parameter, but it is not using it. Instead it just tests whether the Xen PMU initialization on the current cpu did succeed. As this test is done by checking a percpu pointer, preemption needs to be disabled in order to avoid switching the cpu while doing the test. While resuming from suspend() this seems not to be the case: [ 88.082751] ACPI: PM: Low-level resume complete [ 88.087933] ACPI: EC: EC started [ 88.091464] ACPI: PM: Restoring platform NVS memory [ 88.097166] xen_acpi_processor: Uploading Xen processor PM info [ 88.103850] Enabling non-boot CPUs ... [ 88.108128] installing Xen timer for CPU 1 [ 88.112763] BUG: using smp_processor_id() in preemptible [00000000] code: systemd-sleep/7138 [ 88.122256] caller is is_xen_pmu+0x12/0x30 [ 88.126937] CPU: 0 PID: 7138 Comm: systemd-sleep Tainted: G W 5.16.13-2.fc32.qubes.x86_64 #1 [ 88.137939] Hardware name: Star Labs StarBook/StarBook, BIOS 7.97 03/21/2022 [ 88.145930] Call Trace: [ 88.148757] [ 88.151193] dump_stack_lvl+0x48/0x5e [ 88.155381] check_preemption_disabled+0xde/0xe0 [ 88.160641] is_xen_pmu+0x12/0x30 [ 88.164441] xen_smp_intr_init_pv+0x75/0x100 Fix that by replacing is_xen_pmu() by a simple boolean variable which reflects the Xen PMU initialization state on cpu 0. Modify xen_pmu_init() to return early in case it is being called for a cpu other than cpu 0 and the boolean variable not being set. Fixes: bf6dfb154d93 ("xen/PMU: PMU emulation code") Reported-by: Marek Marczykowski-Górecki Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Link: https://lore.kernel.org/r/20220325142002.31789-1-jgross@suse.com Signed-off-by: Boris Ostrovsky --- arch/x86/xen/pmu.c | 10 ++++------ arch/x86/xen/pmu.h | 3 ++- arch/x86/xen/smp_pv.c | 2 +- 3 files changed, 7 insertions(+), 8 deletions(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c index 89dd6b1708b0..21ecbe754cb2 100644 --- a/arch/x86/xen/pmu.c +++ b/arch/x86/xen/pmu.c @@ -506,10 +506,7 @@ irqreturn_t xen_pmu_irq_handler(int irq, void *dev_id) return ret; } -bool is_xen_pmu(int cpu) -{ - return (get_xenpmu_data() != NULL); -} +bool is_xen_pmu; void xen_pmu_init(int cpu) { @@ -520,7 +517,7 @@ void xen_pmu_init(int cpu) BUILD_BUG_ON(sizeof(struct xen_pmu_data) > PAGE_SIZE); - if (xen_hvm_domain()) + if (xen_hvm_domain() || (cpu != 0 && !is_xen_pmu)) return; xenpmu_data = (struct xen_pmu_data *)get_zeroed_page(GFP_KERNEL); @@ -541,7 +538,8 @@ void xen_pmu_init(int cpu) per_cpu(xenpmu_shared, cpu).xenpmu_data = xenpmu_data; per_cpu(xenpmu_shared, cpu).flags = 0; - if (cpu == 0) { + if (!is_xen_pmu) { + is_xen_pmu = true; perf_register_guest_info_callbacks(&xen_guest_cbs); xen_pmu_arch_init(); } diff --git a/arch/x86/xen/pmu.h b/arch/x86/xen/pmu.h index 0e83a160589b..65c58894fc79 100644 --- a/arch/x86/xen/pmu.h +++ b/arch/x86/xen/pmu.h @@ -4,6 +4,8 @@ #include +extern bool is_xen_pmu; + irqreturn_t xen_pmu_irq_handler(int irq, void *dev_id); #ifdef CONFIG_XEN_HAVE_VPMU void xen_pmu_init(int cpu); @@ -12,7 +14,6 @@ void xen_pmu_finish(int cpu); static inline void xen_pmu_init(int cpu) {} static inline void xen_pmu_finish(int cpu) {} #endif -bool is_xen_pmu(int cpu); bool pmu_msr_read(unsigned int msr, uint64_t *val, int *err); bool pmu_msr_write(unsigned int msr, uint32_t low, uint32_t high, int *err); int pmu_apic_update(uint32_t reg); diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 4a6019238ee7..688aa8b6ae29 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -129,7 +129,7 @@ int xen_smp_intr_init_pv(unsigned int cpu) per_cpu(xen_irq_work, cpu).irq = rc; per_cpu(xen_irq_work, cpu).name = callfunc_name; - if (is_xen_pmu(cpu)) { + if (is_xen_pmu) { pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu); rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu, xen_pmu_irq_handler, -- cgit v1.2.1