| Message ID | 20210108121524.656872-4-qperret@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM/arm64: A stage 2 for the host | expand |
On Fri, Jan 08, 2021 at 12:15:01PM +0000, Quentin Perret wrote: > From: Will Deacon <will@kernel.org> > > We will soon need to synchronise multiple CPUs in the hyp text at EL2. > The qspinlock-based locking used by the host is overkill for this purpose > and relies on the kernel's "percpu" implementation for the MCS nodes. > > Implement a simple ticket locking scheme based heavily on the code removed > by commit c11090474d70 ("arm64: locking: Replace ticket lock implementation > with qspinlock"). > > Signed-off-by: Will Deacon <will@kernel.org> > Signed-off-by: Quentin Perret <qperret@google.com> > --- > arch/arm64/kvm/hyp/include/nvhe/spinlock.h | 92 ++++++++++++++++++++++ > 1 file changed, 92 insertions(+) > create mode 100644 arch/arm64/kvm/hyp/include/nvhe/spinlock.h > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/spinlock.h b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h > new file mode 100644 > index 000000000000..7584c397bbac > --- /dev/null > +++ b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h > @@ -0,0 +1,92 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * A stand-alone ticket spinlock implementation for use by the non-VHE > + * KVM hypervisor code running at EL2. > + * > + * Copyright (C) 2020 Google LLC > + * Author: Will Deacon <will@kernel.org> > + * > + * Heavily based on the implementation removed by c11090474d70 which was: > + * Copyright (C) 2012 ARM Ltd. > + */ > + > +#ifndef __ARM64_KVM_NVHE_SPINLOCK_H__ > +#define __ARM64_KVM_NVHE_SPINLOCK_H__ > + > +#include <asm/alternative.h> > +#include <asm/lse.h> > + > +typedef union hyp_spinlock { > + u32 __val; > + struct { > +#ifdef __AARCH64EB__ > + u16 next, owner; > +#else > + u16 owner, next; > + }; > +#endif Looks like I put this #endif in the wrong place; probably needs to be a line higher. Will
On Monday 01 Feb 2021 at 17:28:34 (+0000), Will Deacon wrote: > On Fri, Jan 08, 2021 at 12:15:01PM +0000, Quentin Perret wrote: > > From: Will Deacon <will@kernel.org> > > > > We will soon need to synchronise multiple CPUs in the hyp text at EL2. > > The qspinlock-based locking used by the host is overkill for this purpose > > and relies on the kernel's "percpu" implementation for the MCS nodes. > > > > Implement a simple ticket locking scheme based heavily on the code removed > > by commit c11090474d70 ("arm64: locking: Replace ticket lock implementation > > with qspinlock"). > > > > Signed-off-by: Will Deacon <will@kernel.org> > > Signed-off-by: Quentin Perret <qperret@google.com> > > --- > > arch/arm64/kvm/hyp/include/nvhe/spinlock.h | 92 ++++++++++++++++++++++ > > 1 file changed, 92 insertions(+) > > create mode 100644 arch/arm64/kvm/hyp/include/nvhe/spinlock.h > > > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/spinlock.h b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h > > new file mode 100644 > > index 000000000000..7584c397bbac > > --- /dev/null > > +++ b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h > > @@ -0,0 +1,92 @@ > > +/* SPDX-License-Identifier: GPL-2.0-only */ > > +/* > > + * A stand-alone ticket spinlock implementation for use by the non-VHE > > + * KVM hypervisor code running at EL2. > > + * > > + * Copyright (C) 2020 Google LLC > > + * Author: Will Deacon <will@kernel.org> > > + * > > + * Heavily based on the implementation removed by c11090474d70 which was: > > + * Copyright (C) 2012 ARM Ltd. > > + */ > > + > > +#ifndef __ARM64_KVM_NVHE_SPINLOCK_H__ > > +#define __ARM64_KVM_NVHE_SPINLOCK_H__ > > + > > +#include <asm/alternative.h> > > +#include <asm/lse.h> > > + > > +typedef union hyp_spinlock { > > + u32 __val; > > + struct { > > +#ifdef __AARCH64EB__ > > + u16 next, owner; > > +#else > > + u16 owner, next; > > + }; > > +#endif > > Looks like I put this #endif in the wrong place; probably needs to be a line > higher. Uh oh, missed that too. Fix now merged locally, thanks. Quentin
diff --git a/arch/arm64/kvm/hyp/include/nvhe/spinlock.h b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h new file mode 100644 index 000000000000..7584c397bbac --- /dev/null +++ b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h @@ -0,0 +1,92 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * A stand-alone ticket spinlock implementation for use by the non-VHE + * KVM hypervisor code running at EL2. + * + * Copyright (C) 2020 Google LLC + * Author: Will Deacon <will@kernel.org> + * + * Heavily based on the implementation removed by c11090474d70 which was: + * Copyright (C) 2012 ARM Ltd. + */ + +#ifndef __ARM64_KVM_NVHE_SPINLOCK_H__ +#define __ARM64_KVM_NVHE_SPINLOCK_H__ + +#include <asm/alternative.h> +#include <asm/lse.h> + +typedef union hyp_spinlock { + u32 __val; + struct { +#ifdef __AARCH64EB__ + u16 next, owner; +#else + u16 owner, next; + }; +#endif +} hyp_spinlock_t; + +#define hyp_spin_lock_init(l) \ +do { \ + *(l) = (hyp_spinlock_t){ .__val = 0 }; \ +} while (0) + +static inline void hyp_spin_lock(hyp_spinlock_t *lock) +{ + u32 tmp; + hyp_spinlock_t lockval, newval; + + asm volatile( + /* Atomically increment the next ticket. */ + ARM64_LSE_ATOMIC_INSN( + /* LL/SC */ +" prfm pstl1strm, %3\n" +"1: ldaxr %w0, %3\n" +" add %w1, %w0, #(1 << 16)\n" +" stxr %w2, %w1, %3\n" +" cbnz %w2, 1b\n", + /* LSE atomics */ +" mov %w2, #(1 << 16)\n" +" ldadda %w2, %w0, %3\n" + __nops(3)) + + /* Did we get the lock? */ +" eor %w1, %w0, %w0, ror #16\n" +" cbz %w1, 3f\n" + /* + * No: spin on the owner. Send a local event to avoid missing an + * unlock before the exclusive load. + */ +" sevl\n" +"2: wfe\n" +" ldaxrh %w2, %4\n" +" eor %w1, %w2, %w0, lsr #16\n" +" cbnz %w1, 2b\n" + /* We got the lock. Critical section starts here. */ +"3:" + : "=&r" (lockval), "=&r" (newval), "=&r" (tmp), "+Q" (*lock) + : "Q" (lock->owner) + : "memory"); +} + +static inline void hyp_spin_unlock(hyp_spinlock_t *lock) +{ + u64 tmp; + + asm volatile( + ARM64_LSE_ATOMIC_INSN( + /* LL/SC */ + " ldrh %w1, %0\n" + " add %w1, %w1, #1\n" + " stlrh %w1, %0", + /* LSE atomics */ + " mov %w1, #1\n" + " staddlh %w1, %0\n" + __nops(1)) + : "=Q" (lock->owner), "=&r" (tmp) + : + : "memory"); +} + +#endif /* __ARM64_KVM_NVHE_SPINLOCK_H__ */