From 2fb1e946450a4fef74bb72f360555f7760d816f0 Mon Sep 17 00:00:00 2001 From: Sam Bobroff Date: Tue, 26 Sep 2017 16:47:04 +1000 Subject: [PATCH 1/4] KVM: PPC: Book3S: Fix server always zero from kvmppc_xive_get_xive() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In KVM's XICS-on-XIVE emulation, kvmppc_xive_get_xive() returns the value of state->guest_server as "server". However, this value is not set by it's counterpart kvmppc_xive_set_xive(). When the guest uses this interface to migrate interrupts away from a CPU that is going offline, it sees all interrupts as belonging to CPU 0, so they are left assigned to (now) offline CPUs. This patch removes the guest_server field from the state, and returns act_server in it's place (that is, the CPU actually handling the interrupt, which may differ from the one requested). Fixes: 5af50993850a ("KVM: PPC: Book3S HV: Native usage of the XIVE interrupt controller") Cc: stable@vger.kernel.org Signed-off-by: Sam Bobroff Acked-by: Benjamin Herrenschmidt Signed-off-by: Radim Krčmář --- arch/powerpc/kvm/book3s_xive.c | 5 ++--- arch/powerpc/kvm/book3s_xive.h | 1 - 2 files changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c index 13304622ab1c..bf457843e032 100644 --- a/arch/powerpc/kvm/book3s_xive.c +++ b/arch/powerpc/kvm/book3s_xive.c @@ -622,7 +622,7 @@ int kvmppc_xive_get_xive(struct kvm *kvm, u32 irq, u32 *server, return -EINVAL; state = &sb->irq_state[idx]; arch_spin_lock(&sb->lock); - *server = state->guest_server; + *server = state->act_server; *priority = state->guest_priority; arch_spin_unlock(&sb->lock); @@ -1331,7 +1331,7 @@ static int xive_get_source(struct kvmppc_xive *xive, long irq, u64 addr) xive->saved_src_count++; /* Convert saved state into something compatible with xics */ - val = state->guest_server; + val = state->act_server; prio = state->saved_scan_prio; if (prio == MASKED) { @@ -1507,7 +1507,6 @@ static int xive_set_source(struct kvmppc_xive *xive, long irq, u64 addr) /* First convert prio and mark interrupt as untargetted */ act_prio = xive_prio_from_guest(guest_prio); state->act_priority = MASKED; - state->guest_server = server; /* * We need to drop the lock due to the mutex below. Hopefully diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h index 5938f7644dc1..6ba63f8e8a61 100644 --- a/arch/powerpc/kvm/book3s_xive.h +++ b/arch/powerpc/kvm/book3s_xive.h @@ -35,7 +35,6 @@ struct kvmppc_xive_irq_state { struct xive_irq_data *pt_data; /* XIVE Pass-through associated data */ /* Targetting as set by guest */ - u32 guest_server; /* Current guest selected target */ u8 guest_priority; /* Guest set priority */ u8 saved_priority; /* Saved priority when masking */ From a2b7861bb33b2538420bb5d8554153484d3f961f Mon Sep 17 00:00:00 2001 From: Boqun Feng Date: Tue, 3 Oct 2017 21:36:51 +0800 Subject: [PATCH 2/4] kvm/x86: Avoid async PF preempting the kernel incorrectly MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently, in PREEMPT_COUNT=n kernel, kvm_async_pf_task_wait() could call schedule() to reschedule in some cases. This could result in accidentally ending the current RCU read-side critical section early, causing random memory corruption in the guest, or otherwise preempting the currently running task inside between preempt_disable and preempt_enable. The difficulty to handle this well is because we don't know whether an async PF delivered in a preemptible section or RCU read-side critical section for PREEMPT_COUNT=n, since preempt_disable()/enable() and rcu_read_lock/unlock() are both no-ops in that case. To cure this, we treat any async PF interrupting a kernel context as one that cannot be preempted, preventing kvm_async_pf_task_wait() from choosing the schedule() path in that case. To do so, a second parameter for kvm_async_pf_task_wait() is introduced, so that we know whether it's called from a context interrupting the kernel, and the parameter is set properly in all the callsites. Cc: "Paul E. McKenney" Cc: Peter Zijlstra Cc: Wanpeng Li Cc: stable@vger.kernel.org Signed-off-by: Boqun Feng Signed-off-by: Radim Krčmář --- arch/x86/include/asm/kvm_para.h | 4 ++-- arch/x86/kernel/kvm.c | 14 ++++++++++---- arch/x86/kvm/mmu.c | 2 +- 3 files changed, 13 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index bc62e7cbf1b1..59ad3d132353 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -88,7 +88,7 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1, bool kvm_para_available(void); unsigned int kvm_arch_para_features(void); void __init kvm_guest_init(void); -void kvm_async_pf_task_wait(u32 token); +void kvm_async_pf_task_wait(u32 token, int interrupt_kernel); void kvm_async_pf_task_wake(u32 token); u32 kvm_read_and_reset_pf_reason(void); extern void kvm_disable_steal_time(void); @@ -103,7 +103,7 @@ static inline void kvm_spinlock_init(void) #else /* CONFIG_KVM_GUEST */ #define kvm_guest_init() do {} while (0) -#define kvm_async_pf_task_wait(T) do {} while(0) +#define kvm_async_pf_task_wait(T, I) do {} while(0) #define kvm_async_pf_task_wake(T) do {} while(0) static inline bool kvm_para_available(void) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index e675704fa6f7..8bb9594d0761 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -117,7 +117,11 @@ static struct kvm_task_sleep_node *_find_apf_task(struct kvm_task_sleep_head *b, return NULL; } -void kvm_async_pf_task_wait(u32 token) +/* + * @interrupt_kernel: Is this called from a routine which interrupts the kernel + * (other than user space)? + */ +void kvm_async_pf_task_wait(u32 token, int interrupt_kernel) { u32 key = hash_32(token, KVM_TASK_SLEEP_HASHBITS); struct kvm_task_sleep_head *b = &async_pf_sleepers[key]; @@ -140,8 +144,10 @@ void kvm_async_pf_task_wait(u32 token) n.token = token; n.cpu = smp_processor_id(); - n.halted = is_idle_task(current) || preempt_count() > 1 || - rcu_preempt_depth(); + n.halted = is_idle_task(current) || + (IS_ENABLED(CONFIG_PREEMPT_COUNT) + ? preempt_count() > 1 || rcu_preempt_depth() + : interrupt_kernel); init_swait_queue_head(&n.wq); hlist_add_head(&n.link, &b->list); raw_spin_unlock(&b->lock); @@ -269,7 +275,7 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code) case KVM_PV_REASON_PAGE_NOT_PRESENT: /* page is swapped out by the host. */ prev_state = exception_enter(); - kvm_async_pf_task_wait((u32)read_cr2()); + kvm_async_pf_task_wait((u32)read_cr2(), !user_mode(regs)); exception_exit(prev_state); break; case KVM_PV_REASON_PAGE_READY: diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index eca30c1eb1d9..106d4a029a8a 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3837,7 +3837,7 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code, case KVM_PV_REASON_PAGE_NOT_PRESENT: vcpu->arch.apf.host_apf_reason = 0; local_irq_disable(); - kvm_async_pf_task_wait(fault_address); + kvm_async_pf_task_wait(fault_address, 0); local_irq_enable(); break; case KVM_PV_REASON_PAGE_READY: From f26e60167d8b5b1c67b3efd4cb5672da446bdb0e Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Wed, 4 Oct 2017 10:39:05 -0500 Subject: [PATCH 3/4] x86/kvm: Move kvm_fastop_exception to .fixup section MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When compiling the kernel with the '-frecord-gcc-switches' flag, objtool complains: arch/x86/kvm/emulate.o: warning: objtool: .GCC.command.line+0x0: special: can't find new instruction And also the kernel fails to link. The problem is that the 'kvm_fastop_exception' code gets placed into the throwaway '.GCC.command.line' section instead of '.text'. Exception fixup code is conventionally placed in the '.fixup' section, so put it there where it belongs. Reported-and-tested-by: Guenter Roeck Signed-off-by: Josh Poimboeuf Reviewed-by: Paolo Bonzini Signed-off-by: Radim Krčmář --- arch/x86/kvm/emulate.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index a36254cbf776..d90cdc77e077 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -425,8 +425,10 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *)); #op " %al \n\t" \ FOP_RET -asm(".global kvm_fastop_exception \n" - "kvm_fastop_exception: xor %esi, %esi; ret"); +asm(".pushsection .fixup, \"ax\"\n" + ".global kvm_fastop_exception \n" + "kvm_fastop_exception: xor %esi, %esi; ret\n" + ".popsection"); FOP_START(setcc) FOP_SETCC(seto) From e42eef4ba38806b18c4a74f0c276fb2e0b548173 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Wed, 4 Oct 2017 12:28:18 +0200 Subject: [PATCH 4/4] KVM: add X86_LOCAL_APIC dependency MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The rework of the posted interrupt handling broke building without support for the local APIC: ERROR: "boot_cpu_physical_apicid" [arch/x86/kvm/kvm-intel.ko] undefined! That configuration is probably not particularly useful anyway, so we can avoid the randconfig failures by adding a Kconfig dependency. Fixes: 8b306e2f3c41 ("KVM: VMX: avoid double list add with VT-d posted interrupts") Signed-off-by: Arnd Bergmann Signed-off-by: Radim Krčmář --- arch/x86/kvm/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index 3ea624452f93..3c48bc8bf08c 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -23,6 +23,7 @@ config KVM depends on HIGH_RES_TIMERS # for TASKSTATS/TASK_DELAY_ACCT: depends on NET && MULTIUSER + depends on X86_LOCAL_APIC select PREEMPT_NOTIFIERS select MMU_NOTIFIER select ANON_INODES