| Message ID | 20230910082911.3378782-9-guoren@kernel.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | riscv: Add Native/Paravirt qspinlock support | expand |
| Context | Check | Description |
|---|---|---|
| conchuod/tree_selection | fail | Failed to apply to next/pending-fixes, riscv/for-next or riscv/master |
On Sun, Sep 10, 2023 at 04:29:02AM -0400, guoren@kernel.org wrote: > From: Guo Ren <guoren@linux.alibaba.com> > > Add a static key controlling whether virt_spin_lock() should be > called or not. When running on bare metal set the new key to > false. > > The KVM guests fall back to a Test-and-Set spinlock, because fair > locks have horrible lock 'holder' preemption issues. The > virt_spin_lock_key would shortcut for the > queued_spin_lock_slowpath() function that allow virt_spin_lock to > hijack it. > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > Signed-off-by: Guo Ren <guoren@kernel.org> > --- > .../admin-guide/kernel-parameters.txt | 4 +++ > arch/riscv/include/asm/sbi.h | 8 +++++ > arch/riscv/include/asm/spinlock.h | 22 ++++++++++++++ > arch/riscv/kernel/sbi.c | 2 +- > arch/riscv/kernel/setup.c | 30 ++++++++++++++++++- > 5 files changed, 64 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 61cacb8dfd0e..f75bedc50e00 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -3927,6 +3927,10 @@ > no_uaccess_flush > [PPC] Don't flush the L1-D cache after accessing user data. > > + no_virt_spin [RISC-V] Disable virt_spin_lock in KVM guest to use > + native_queued_spinlock when the nopvspin option is enabled. > + This would help vcpu=pcpu scenarios. > + > novmcoredd [KNL,KDUMP] > Disable device dump. Device dump allows drivers to > append dump data to vmcore so you can collect driver > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h > index 501e06e52078..e0233b3d7a5f 100644 > --- a/arch/riscv/include/asm/sbi.h > +++ b/arch/riscv/include/asm/sbi.h > @@ -50,6 +50,13 @@ enum sbi_ext_base_fid { > SBI_EXT_BASE_GET_MIMPID, > }; > > +enum sbi_ext_base_impl_id { > + SBI_EXT_BASE_IMPL_ID_BBL = 0, > + SBI_EXT_BASE_IMPL_ID_OPENSBI, > + SBI_EXT_BASE_IMPL_ID_XVISOR, > + SBI_EXT_BASE_IMPL_ID_KVM, > +}; > + > enum sbi_ext_time_fid { > SBI_EXT_TIME_SET_TIMER = 0, > }; > @@ -269,6 +276,7 @@ int sbi_console_getchar(void); > long sbi_get_mvendorid(void); > long sbi_get_marchid(void); > long sbi_get_mimpid(void); > +long sbi_get_firmware_id(void); > void sbi_set_timer(uint64_t stime_value); > void sbi_shutdown(void); > void sbi_send_ipi(unsigned int cpu); > diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h > index 8ea0fee80652..6b38d6616f14 100644 > --- a/arch/riscv/include/asm/spinlock.h > +++ b/arch/riscv/include/asm/spinlock.h > @@ -4,6 +4,28 @@ > #define __ASM_RISCV_SPINLOCK_H > > #ifdef CONFIG_QUEUED_SPINLOCKS > +/* > + * The KVM guests fall back to a Test-and-Set spinlock, because fair locks > + * have horrible lock 'holder' preemption issues. The virt_spin_lock_key > + * would shortcut for the queued_spin_lock_slowpath() function that allow > + * virt_spin_lock to hijack it. > + */ > +DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); > + > +#define virt_spin_lock virt_spin_lock > +static inline bool virt_spin_lock(struct qspinlock *lock) > +{ > + if (!static_branch_likely(&virt_spin_lock_key)) > + return false; > + > + do { > + while (atomic_read(&lock->val) != 0) > + cpu_relax(); > + } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0); > + > + return true; > +} > + > #define _Q_PENDING_LOOPS (1 << 9) > #endif > > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c > index 88eea3a99ee0..cdd45edc8db4 100644 > --- a/arch/riscv/kernel/sbi.c > +++ b/arch/riscv/kernel/sbi.c > @@ -555,7 +555,7 @@ static inline long sbi_get_spec_version(void) > return __sbi_base_ecall(SBI_EXT_BASE_GET_SPEC_VERSION); > } > > -static inline long sbi_get_firmware_id(void) > +long sbi_get_firmware_id(void) > { > return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_ID); > } > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > index 0f084f037651..c57d15b05160 100644 > --- a/arch/riscv/kernel/setup.c > +++ b/arch/riscv/kernel/setup.c > @@ -26,6 +26,7 @@ > #include <asm/alternative.h> > #include <asm/cacheflush.h> > #include <asm/cpu_ops.h> > +#include <asm/cpufeature.h> > #include <asm/early_ioremap.h> > #include <asm/pgtable.h> > #include <asm/setup.h> > @@ -283,16 +284,43 @@ DEFINE_STATIC_KEY_TRUE(combo_qspinlock_key); > EXPORT_SYMBOL(combo_qspinlock_key); > #endif > > +#ifdef CONFIG_QUEUED_SPINLOCKS > +static bool no_virt_spin_key = false; I suggest no _key, also there is no need for "= false". To be consistent with enable_qspinlock, I also suggest adding __ro_after_init: static bool no_virt_spin __ro_after_init; > +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); > + > +static int __init no_virt_spin_setup(char *p) > +{ > + no_virt_spin_key = true; > + > + return 0; > +} > +early_param("no_virt_spin", no_virt_spin_setup); > + > +static void __init virt_spin_lock_init(void) > +{ > + if (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM || > + no_virt_spin_key) > + static_branch_disable(&virt_spin_lock_key); > + else > + pr_info("Enable virt_spin_lock\n"); > +} > +#endif > + A new virt_no_spin kernel parameter was introduced, but without CONFIG_QUEUED_SPINLOCKS it will silently fail. I would suggest an #else clause here with a function to print an error / warning message about no_virt_spin being invalid in this scenario. It will probably help future debugging. > static void __init riscv_spinlock_init(void) > { > #ifdef CONFIG_RISCV_COMBO_SPINLOCKS > - if (!enable_qspinlock_key) { > + if (!enable_qspinlock_key && > + (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)) { > static_branch_disable(&combo_qspinlock_key); > pr_info("Ticket spinlock: enabled\n"); > } else { > pr_info("Queued spinlock: enabled\n"); > } > #endif > + > +#ifdef CONFIG_QUEUED_SPINLOCKS > + virt_spin_lock_init(); > +#endif > } > > extern void __init init_rt_signal_env(void); > -- > 2.36.1 > I am probably missing something out, but it looks to me that this patch is causing 2 different changes: 1 - Enabling no_virt_spin parameter 2 - Disabling queued spinlocks for some firmware_id Wouldn't be better to split those changes in multiple patches? Or am I missing the point on why they need to be together? Thanks! Leo
On Thu, Sep 14, 2023 at 4:02 PM Leonardo Bras <leobras@redhat.com> wrote: > > On Sun, Sep 10, 2023 at 04:29:02AM -0400, guoren@kernel.org wrote: > > From: Guo Ren <guoren@linux.alibaba.com> > > > > Add a static key controlling whether virt_spin_lock() should be > > called or not. When running on bare metal set the new key to > > false. > > > > The KVM guests fall back to a Test-and-Set spinlock, because fair > > locks have horrible lock 'holder' preemption issues. The > > virt_spin_lock_key would shortcut for the > > queued_spin_lock_slowpath() function that allow virt_spin_lock to > > hijack it. > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > Signed-off-by: Guo Ren <guoren@kernel.org> > > --- > > .../admin-guide/kernel-parameters.txt | 4 +++ > > arch/riscv/include/asm/sbi.h | 8 +++++ > > arch/riscv/include/asm/spinlock.h | 22 ++++++++++++++ > > arch/riscv/kernel/sbi.c | 2 +- > > arch/riscv/kernel/setup.c | 30 ++++++++++++++++++- > > 5 files changed, 64 insertions(+), 2 deletions(-) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index 61cacb8dfd0e..f75bedc50e00 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -3927,6 +3927,10 @@ > > no_uaccess_flush > > [PPC] Don't flush the L1-D cache after accessing user data. > > > > + no_virt_spin [RISC-V] Disable virt_spin_lock in KVM guest to use > > + native_queued_spinlock when the nopvspin option is enabled. > > + This would help vcpu=pcpu scenarios. > > + > > novmcoredd [KNL,KDUMP] > > Disable device dump. Device dump allows drivers to > > append dump data to vmcore so you can collect driver > > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h > > index 501e06e52078..e0233b3d7a5f 100644 > > --- a/arch/riscv/include/asm/sbi.h > > +++ b/arch/riscv/include/asm/sbi.h > > @@ -50,6 +50,13 @@ enum sbi_ext_base_fid { > > SBI_EXT_BASE_GET_MIMPID, > > }; > > > > +enum sbi_ext_base_impl_id { > > + SBI_EXT_BASE_IMPL_ID_BBL = 0, > > + SBI_EXT_BASE_IMPL_ID_OPENSBI, > > + SBI_EXT_BASE_IMPL_ID_XVISOR, > > + SBI_EXT_BASE_IMPL_ID_KVM, > > +}; > > + > > enum sbi_ext_time_fid { > > SBI_EXT_TIME_SET_TIMER = 0, > > }; > > @@ -269,6 +276,7 @@ int sbi_console_getchar(void); > > long sbi_get_mvendorid(void); > > long sbi_get_marchid(void); > > long sbi_get_mimpid(void); > > +long sbi_get_firmware_id(void); > > void sbi_set_timer(uint64_t stime_value); > > void sbi_shutdown(void); > > void sbi_send_ipi(unsigned int cpu); > > diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h > > index 8ea0fee80652..6b38d6616f14 100644 > > --- a/arch/riscv/include/asm/spinlock.h > > +++ b/arch/riscv/include/asm/spinlock.h > > @@ -4,6 +4,28 @@ > > #define __ASM_RISCV_SPINLOCK_H > > > > #ifdef CONFIG_QUEUED_SPINLOCKS > > +/* > > + * The KVM guests fall back to a Test-and-Set spinlock, because fair locks > > + * have horrible lock 'holder' preemption issues. The virt_spin_lock_key > > + * would shortcut for the queued_spin_lock_slowpath() function that allow > > + * virt_spin_lock to hijack it. > > + */ > > +DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); > > + > > +#define virt_spin_lock virt_spin_lock > > +static inline bool virt_spin_lock(struct qspinlock *lock) > > +{ > > + if (!static_branch_likely(&virt_spin_lock_key)) > > + return false; > > + > > + do { > > + while (atomic_read(&lock->val) != 0) > > + cpu_relax(); > > + } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0); > > + > > + return true; > > +} > > + > > #define _Q_PENDING_LOOPS (1 << 9) > > #endif > > > > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c > > index 88eea3a99ee0..cdd45edc8db4 100644 > > --- a/arch/riscv/kernel/sbi.c > > +++ b/arch/riscv/kernel/sbi.c > > @@ -555,7 +555,7 @@ static inline long sbi_get_spec_version(void) > > return __sbi_base_ecall(SBI_EXT_BASE_GET_SPEC_VERSION); > > } > > > > -static inline long sbi_get_firmware_id(void) > > +long sbi_get_firmware_id(void) > > { > > return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_ID); > > } > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > > index 0f084f037651..c57d15b05160 100644 > > --- a/arch/riscv/kernel/setup.c > > +++ b/arch/riscv/kernel/setup.c > > @@ -26,6 +26,7 @@ > > #include <asm/alternative.h> > > #include <asm/cacheflush.h> > > #include <asm/cpu_ops.h> > > +#include <asm/cpufeature.h> > > #include <asm/early_ioremap.h> > > #include <asm/pgtable.h> > > #include <asm/setup.h> > > @@ -283,16 +284,43 @@ DEFINE_STATIC_KEY_TRUE(combo_qspinlock_key); > > EXPORT_SYMBOL(combo_qspinlock_key); > > #endif > > > > +#ifdef CONFIG_QUEUED_SPINLOCKS > > +static bool no_virt_spin_key = false; > > I suggest no _key, also there is no need for "= false". > To be consistent with enable_qspinlock, I also suggest > adding __ro_after_init: > > static bool no_virt_spin __ro_after_init; okay. > > > > > +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); > > + > > +static int __init no_virt_spin_setup(char *p) > > +{ > > + no_virt_spin_key = true; > > + > > + return 0; > > +} > > +early_param("no_virt_spin", no_virt_spin_setup); > > + > > +static void __init virt_spin_lock_init(void) > > +{ > > + if (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM || > > + no_virt_spin_key) > > + static_branch_disable(&virt_spin_lock_key); > > + else > > + pr_info("Enable virt_spin_lock\n"); > > +} > > +#endif > > + > > A new virt_no_spin kernel parameter was introduced, but without > CONFIG_QUEUED_SPINLOCKS it will silently fail. > > I would suggest an #else clause here with a function to print an error / > warning message about no_virt_spin being invalid in this scenario. > It will probably help future debugging. If CONFIG_QUEUED_SPINLOCKS=n, no_virt_spin should be quiet. The no_virt_spin is one path of qspinlock. > > > > static void __init riscv_spinlock_init(void) > > { > > #ifdef CONFIG_RISCV_COMBO_SPINLOCKS > > - if (!enable_qspinlock_key) { > > + if (!enable_qspinlock_key && > > + (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)) { > > static_branch_disable(&combo_qspinlock_key); > > pr_info("Ticket spinlock: enabled\n"); > > } else { > > pr_info("Queued spinlock: enabled\n"); > > } > > #endif > > + > > +#ifdef CONFIG_QUEUED_SPINLOCKS > > + virt_spin_lock_init(); > > +#endif > > } > > > > extern void __init init_rt_signal_env(void); > > -- > > 2.36.1 > > > > I am probably missing something out, but it looks to me that this patch is > causing 2 different changes: > 1 - Enabling no_virt_spin parameter > 2 - Disabling queued spinlocks for some firmware_id > > Wouldn't be better to split those changes in multiple patches? > Or am I missing the point on why they need to be together? > > Thanks! > Leo >
On Sun, Sep 17, 2023 at 11:12:31PM +0800, Guo Ren wrote: > On Thu, Sep 14, 2023 at 4:02 PM Leonardo Bras <leobras@redhat.com> wrote: > > > > On Sun, Sep 10, 2023 at 04:29:02AM -0400, guoren@kernel.org wrote: > > > From: Guo Ren <guoren@linux.alibaba.com> > > > > > > Add a static key controlling whether virt_spin_lock() should be > > > called or not. When running on bare metal set the new key to > > > false. > > > > > > The KVM guests fall back to a Test-and-Set spinlock, because fair > > > locks have horrible lock 'holder' preemption issues. The > > > virt_spin_lock_key would shortcut for the > > > queued_spin_lock_slowpath() function that allow virt_spin_lock to > > > hijack it. > > > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > > Signed-off-by: Guo Ren <guoren@kernel.org> > > > --- > > > .../admin-guide/kernel-parameters.txt | 4 +++ > > > arch/riscv/include/asm/sbi.h | 8 +++++ > > > arch/riscv/include/asm/spinlock.h | 22 ++++++++++++++ > > > arch/riscv/kernel/sbi.c | 2 +- > > > arch/riscv/kernel/setup.c | 30 ++++++++++++++++++- > > > 5 files changed, 64 insertions(+), 2 deletions(-) > > > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > > index 61cacb8dfd0e..f75bedc50e00 100644 > > > --- a/Documentation/admin-guide/kernel-parameters.txt > > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > > @@ -3927,6 +3927,10 @@ > > > no_uaccess_flush > > > [PPC] Don't flush the L1-D cache after accessing user data. > > > > > > + no_virt_spin [RISC-V] Disable virt_spin_lock in KVM guest to use > > > + native_queued_spinlock when the nopvspin option is enabled. > > > + This would help vcpu=pcpu scenarios. > > > + > > > novmcoredd [KNL,KDUMP] > > > Disable device dump. Device dump allows drivers to > > > append dump data to vmcore so you can collect driver > > > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h > > > index 501e06e52078..e0233b3d7a5f 100644 > > > --- a/arch/riscv/include/asm/sbi.h > > > +++ b/arch/riscv/include/asm/sbi.h > > > @@ -50,6 +50,13 @@ enum sbi_ext_base_fid { > > > SBI_EXT_BASE_GET_MIMPID, > > > }; > > > > > > +enum sbi_ext_base_impl_id { > > > + SBI_EXT_BASE_IMPL_ID_BBL = 0, > > > + SBI_EXT_BASE_IMPL_ID_OPENSBI, > > > + SBI_EXT_BASE_IMPL_ID_XVISOR, > > > + SBI_EXT_BASE_IMPL_ID_KVM, > > > +}; > > > + > > > enum sbi_ext_time_fid { > > > SBI_EXT_TIME_SET_TIMER = 0, > > > }; > > > @@ -269,6 +276,7 @@ int sbi_console_getchar(void); > > > long sbi_get_mvendorid(void); > > > long sbi_get_marchid(void); > > > long sbi_get_mimpid(void); > > > +long sbi_get_firmware_id(void); > > > void sbi_set_timer(uint64_t stime_value); > > > void sbi_shutdown(void); > > > void sbi_send_ipi(unsigned int cpu); > > > diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h > > > index 8ea0fee80652..6b38d6616f14 100644 > > > --- a/arch/riscv/include/asm/spinlock.h > > > +++ b/arch/riscv/include/asm/spinlock.h > > > @@ -4,6 +4,28 @@ > > > #define __ASM_RISCV_SPINLOCK_H > > > > > > #ifdef CONFIG_QUEUED_SPINLOCKS > > > +/* > > > + * The KVM guests fall back to a Test-and-Set spinlock, because fair locks > > > + * have horrible lock 'holder' preemption issues. The virt_spin_lock_key > > > + * would shortcut for the queued_spin_lock_slowpath() function that allow > > > + * virt_spin_lock to hijack it. > > > + */ > > > +DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); > > > + > > > +#define virt_spin_lock virt_spin_lock > > > +static inline bool virt_spin_lock(struct qspinlock *lock) > > > +{ > > > + if (!static_branch_likely(&virt_spin_lock_key)) > > > + return false; > > > + > > > + do { > > > + while (atomic_read(&lock->val) != 0) > > > + cpu_relax(); > > > + } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0); > > > + > > > + return true; > > > +} > > > + > > > #define _Q_PENDING_LOOPS (1 << 9) > > > #endif > > > > > > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c > > > index 88eea3a99ee0..cdd45edc8db4 100644 > > > --- a/arch/riscv/kernel/sbi.c > > > +++ b/arch/riscv/kernel/sbi.c > > > @@ -555,7 +555,7 @@ static inline long sbi_get_spec_version(void) > > > return __sbi_base_ecall(SBI_EXT_BASE_GET_SPEC_VERSION); > > > } > > > > > > -static inline long sbi_get_firmware_id(void) > > > +long sbi_get_firmware_id(void) > > > { > > > return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_ID); > > > } > > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > > > index 0f084f037651..c57d15b05160 100644 > > > --- a/arch/riscv/kernel/setup.c > > > +++ b/arch/riscv/kernel/setup.c > > > @@ -26,6 +26,7 @@ > > > #include <asm/alternative.h> > > > #include <asm/cacheflush.h> > > > #include <asm/cpu_ops.h> > > > +#include <asm/cpufeature.h> > > > #include <asm/early_ioremap.h> > > > #include <asm/pgtable.h> > > > #include <asm/setup.h> > > > @@ -283,16 +284,43 @@ DEFINE_STATIC_KEY_TRUE(combo_qspinlock_key); > > > EXPORT_SYMBOL(combo_qspinlock_key); > > > #endif > > > > > > +#ifdef CONFIG_QUEUED_SPINLOCKS > > > +static bool no_virt_spin_key = false; > > > > I suggest no _key, also there is no need for "= false". > > To be consistent with enable_qspinlock, I also suggest > > adding __ro_after_init: > > > > static bool no_virt_spin __ro_after_init; > okay. > > > > > > > > > > +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); > > > + > > > +static int __init no_virt_spin_setup(char *p) > > > +{ > > > + no_virt_spin_key = true; > > > + > > > + return 0; > > > +} > > > +early_param("no_virt_spin", no_virt_spin_setup); > > > + > > > +static void __init virt_spin_lock_init(void) > > > +{ > > > + if (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM || > > > + no_virt_spin_key) > > > + static_branch_disable(&virt_spin_lock_key); > > > + else > > > + pr_info("Enable virt_spin_lock\n"); > > > +} > > > +#endif > > > + > > > > A new virt_no_spin kernel parameter was introduced, but without > > CONFIG_QUEUED_SPINLOCKS it will silently fail. > > > > I would suggest an #else clause here with a function to print an error / > > warning message about no_virt_spin being invalid in this scenario. > > It will probably help future debugging. > If CONFIG_QUEUED_SPINLOCKS=n, no_virt_spin should be quiet. The > no_virt_spin is one path of qspinlock. IIUC having no_virt_spin being passed as parameter to a kernel with CONFIG_QUEUED_SPINLOCKS=n is not supposed to have any warning this parameter is useless. I was just thinking it would be nice to have this warning during debugging, but if it's standard practice then I am ok with this. > > > > > > > > static void __init riscv_spinlock_init(void) > > > { > > > #ifdef CONFIG_RISCV_COMBO_SPINLOCKS > > > - if (!enable_qspinlock_key) { > > > + if (!enable_qspinlock_key && > > > + (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)) { > > > static_branch_disable(&combo_qspinlock_key); > > > pr_info("Ticket spinlock: enabled\n"); > > > } else { > > > pr_info("Queued spinlock: enabled\n"); > > > } > > > #endif > > > + > > > +#ifdef CONFIG_QUEUED_SPINLOCKS > > > + virt_spin_lock_init(); > > > +#endif > > > } > > > > > > extern void __init init_rt_signal_env(void); > > > -- > > > 2.36.1 > > > > > > > I am probably missing something out, but it looks to me that this patch is > > causing 2 different changes: > > 1 - Enabling no_virt_spin parameter > > 2 - Disabling queued spinlocks for some firmware_id > > > > Wouldn't be better to split those changes in multiple patches? > > Or am I missing the point on why they need to be together? ^ Want your input on this Thanks! Leo > > > > Thanks! > > Leo > > > > > -- > Best Regards > Guo Ren >
On Tue, Sep 19, 2023 at 1:30 PM Leonardo Bras <leobras@redhat.com> wrote: > > On Sun, Sep 17, 2023 at 11:12:31PM +0800, Guo Ren wrote: > > On Thu, Sep 14, 2023 at 4:02 PM Leonardo Bras <leobras@redhat.com> wrote: > > > > > > On Sun, Sep 10, 2023 at 04:29:02AM -0400, guoren@kernel.org wrote: > > > > From: Guo Ren <guoren@linux.alibaba.com> > > > > > > > > Add a static key controlling whether virt_spin_lock() should be > > > > called or not. When running on bare metal set the new key to > > > > false. > > > > > > > > The KVM guests fall back to a Test-and-Set spinlock, because fair > > > > locks have horrible lock 'holder' preemption issues. The > > > > virt_spin_lock_key would shortcut for the > > > > queued_spin_lock_slowpath() function that allow virt_spin_lock to > > > > hijack it. > > > > > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > > > Signed-off-by: Guo Ren <guoren@kernel.org> > > > > --- > > > > .../admin-guide/kernel-parameters.txt | 4 +++ > > > > arch/riscv/include/asm/sbi.h | 8 +++++ > > > > arch/riscv/include/asm/spinlock.h | 22 ++++++++++++++ > > > > arch/riscv/kernel/sbi.c | 2 +- > > > > arch/riscv/kernel/setup.c | 30 ++++++++++++++++++- > > > > 5 files changed, 64 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > > > index 61cacb8dfd0e..f75bedc50e00 100644 > > > > --- a/Documentation/admin-guide/kernel-parameters.txt > > > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > > > @@ -3927,6 +3927,10 @@ > > > > no_uaccess_flush > > > > [PPC] Don't flush the L1-D cache after accessing user data. > > > > > > > > + no_virt_spin [RISC-V] Disable virt_spin_lock in KVM guest to use > > > > + native_queued_spinlock when the nopvspin option is enabled. > > > > + This would help vcpu=pcpu scenarios. > > > > + > > > > novmcoredd [KNL,KDUMP] > > > > Disable device dump. Device dump allows drivers to > > > > append dump data to vmcore so you can collect driver > > > > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h > > > > index 501e06e52078..e0233b3d7a5f 100644 > > > > --- a/arch/riscv/include/asm/sbi.h > > > > +++ b/arch/riscv/include/asm/sbi.h > > > > @@ -50,6 +50,13 @@ enum sbi_ext_base_fid { > > > > SBI_EXT_BASE_GET_MIMPID, > > > > }; > > > > > > > > +enum sbi_ext_base_impl_id { > > > > + SBI_EXT_BASE_IMPL_ID_BBL = 0, > > > > + SBI_EXT_BASE_IMPL_ID_OPENSBI, > > > > + SBI_EXT_BASE_IMPL_ID_XVISOR, > > > > + SBI_EXT_BASE_IMPL_ID_KVM, > > > > +}; > > > > + > > > > enum sbi_ext_time_fid { > > > > SBI_EXT_TIME_SET_TIMER = 0, > > > > }; > > > > @@ -269,6 +276,7 @@ int sbi_console_getchar(void); > > > > long sbi_get_mvendorid(void); > > > > long sbi_get_marchid(void); > > > > long sbi_get_mimpid(void); > > > > +long sbi_get_firmware_id(void); > > > > void sbi_set_timer(uint64_t stime_value); > > > > void sbi_shutdown(void); > > > > void sbi_send_ipi(unsigned int cpu); > > > > diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h > > > > index 8ea0fee80652..6b38d6616f14 100644 > > > > --- a/arch/riscv/include/asm/spinlock.h > > > > +++ b/arch/riscv/include/asm/spinlock.h > > > > @@ -4,6 +4,28 @@ > > > > #define __ASM_RISCV_SPINLOCK_H > > > > > > > > #ifdef CONFIG_QUEUED_SPINLOCKS > > > > +/* > > > > + * The KVM guests fall back to a Test-and-Set spinlock, because fair locks > > > > + * have horrible lock 'holder' preemption issues. The virt_spin_lock_key > > > > + * would shortcut for the queued_spin_lock_slowpath() function that allow > > > > + * virt_spin_lock to hijack it. > > > > + */ > > > > +DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); > > > > + > > > > +#define virt_spin_lock virt_spin_lock > > > > +static inline bool virt_spin_lock(struct qspinlock *lock) > > > > +{ > > > > + if (!static_branch_likely(&virt_spin_lock_key)) > > > > + return false; > > > > + > > > > + do { > > > > + while (atomic_read(&lock->val) != 0) > > > > + cpu_relax(); > > > > + } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0); > > > > + > > > > + return true; > > > > +} > > > > + > > > > #define _Q_PENDING_LOOPS (1 << 9) > > > > #endif > > > > > > > > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c > > > > index 88eea3a99ee0..cdd45edc8db4 100644 > > > > --- a/arch/riscv/kernel/sbi.c > > > > +++ b/arch/riscv/kernel/sbi.c > > > > @@ -555,7 +555,7 @@ static inline long sbi_get_spec_version(void) > > > > return __sbi_base_ecall(SBI_EXT_BASE_GET_SPEC_VERSION); > > > > } > > > > > > > > -static inline long sbi_get_firmware_id(void) > > > > +long sbi_get_firmware_id(void) > > > > { > > > > return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_ID); > > > > } > > > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > > > > index 0f084f037651..c57d15b05160 100644 > > > > --- a/arch/riscv/kernel/setup.c > > > > +++ b/arch/riscv/kernel/setup.c > > > > @@ -26,6 +26,7 @@ > > > > #include <asm/alternative.h> > > > > #include <asm/cacheflush.h> > > > > #include <asm/cpu_ops.h> > > > > +#include <asm/cpufeature.h> > > > > #include <asm/early_ioremap.h> > > > > #include <asm/pgtable.h> > > > > #include <asm/setup.h> > > > > @@ -283,16 +284,43 @@ DEFINE_STATIC_KEY_TRUE(combo_qspinlock_key); > > > > EXPORT_SYMBOL(combo_qspinlock_key); > > > > #endif > > > > > > > > +#ifdef CONFIG_QUEUED_SPINLOCKS > > > > +static bool no_virt_spin_key = false; > > > > > > I suggest no _key, also there is no need for "= false". > > > To be consistent with enable_qspinlock, I also suggest > > > adding __ro_after_init: > > > > > > static bool no_virt_spin __ro_after_init; > > okay. > > > > > > > > > > > > > > > +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); > > > > + > > > > +static int __init no_virt_spin_setup(char *p) > > > > +{ > > > > + no_virt_spin_key = true; > > > > + > > > > + return 0; > > > > +} > > > > +early_param("no_virt_spin", no_virt_spin_setup); > > > > + > > > > +static void __init virt_spin_lock_init(void) > > > > +{ > > > > + if (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM || > > > > + no_virt_spin_key) > > > > + static_branch_disable(&virt_spin_lock_key); > > > > + else > > > > + pr_info("Enable virt_spin_lock\n"); > > > > +} > > > > +#endif > > > > + > > > > > > A new virt_no_spin kernel parameter was introduced, but without > > > CONFIG_QUEUED_SPINLOCKS it will silently fail. > > > > > > I would suggest an #else clause here with a function to print an error / > > > warning message about no_virt_spin being invalid in this scenario. > > > It will probably help future debugging. > > If CONFIG_QUEUED_SPINLOCKS=n, no_virt_spin should be quiet. The > > no_virt_spin is one path of qspinlock. > > IIUC having no_virt_spin being passed as parameter to a kernel with > CONFIG_QUEUED_SPINLOCKS=n is not supposed to have any warning this > parameter is useless. > > I was just thinking it would be nice to have this warning during debugging, > but if it's standard practice then I am ok with this. Yes, I think it's okay, e.g., x86: early_param("hv_nopvspin", hv_parse_nopvspin); depends on CONFIG_PARAVIRT_SPINLOCKS=y > > > > > > > > > > > > > static void __init riscv_spinlock_init(void) > > > > { > > > > #ifdef CONFIG_RISCV_COMBO_SPINLOCKS > > > > - if (!enable_qspinlock_key) { > > > > + if (!enable_qspinlock_key && > > > > + (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)) { > > > > static_branch_disable(&combo_qspinlock_key); > > > > pr_info("Ticket spinlock: enabled\n"); > > > > } else { > > > > pr_info("Queued spinlock: enabled\n"); > > > > } > > > > #endif > > > > + > > > > +#ifdef CONFIG_QUEUED_SPINLOCKS > > > > + virt_spin_lock_init(); > > > > +#endif > > > > } > > > > > > > > extern void __init init_rt_signal_env(void); > > > > -- > > > > 2.36.1 > > > > > > > > > > I am probably missing something out, but it looks to me that this patch is > > > causing 2 different changes: > > > 1 - Enabling no_virt_spin parameter > > > 2 - Disabling queued spinlocks for some firmware_id > > > > > > Wouldn't be better to split those changes in multiple patches? > > > Or am I missing the point on why they need to be together? > > ^ Want your input on this Sorry, I missed that. Okay, I would split those changes. > > Thanks! > Leo > > > > > > > Thanks! > > > Leo > > > > > > > > > -- > > Best Regards > > Guo Ren > > >
On Tue, Sep 19, 2023 at 04:04:48PM +0800, Guo Ren wrote: > On Tue, Sep 19, 2023 at 1:30 PM Leonardo Bras <leobras@redhat.com> wrote: > > > > On Sun, Sep 17, 2023 at 11:12:31PM +0800, Guo Ren wrote: > > > On Thu, Sep 14, 2023 at 4:02 PM Leonardo Bras <leobras@redhat.com> wrote: > > > > > > > > On Sun, Sep 10, 2023 at 04:29:02AM -0400, guoren@kernel.org wrote: > > > > > From: Guo Ren <guoren@linux.alibaba.com> > > > > > > > > > > Add a static key controlling whether virt_spin_lock() should be > > > > > called or not. When running on bare metal set the new key to > > > > > false. > > > > > > > > > > The KVM guests fall back to a Test-and-Set spinlock, because fair > > > > > locks have horrible lock 'holder' preemption issues. The > > > > > virt_spin_lock_key would shortcut for the > > > > > queued_spin_lock_slowpath() function that allow virt_spin_lock to > > > > > hijack it. > > > > > > > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > > > > Signed-off-by: Guo Ren <guoren@kernel.org> > > > > > --- > > > > > .../admin-guide/kernel-parameters.txt | 4 +++ > > > > > arch/riscv/include/asm/sbi.h | 8 +++++ > > > > > arch/riscv/include/asm/spinlock.h | 22 ++++++++++++++ > > > > > arch/riscv/kernel/sbi.c | 2 +- > > > > > arch/riscv/kernel/setup.c | 30 ++++++++++++++++++- > > > > > 5 files changed, 64 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > > > > index 61cacb8dfd0e..f75bedc50e00 100644 > > > > > --- a/Documentation/admin-guide/kernel-parameters.txt > > > > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > > > > @@ -3927,6 +3927,10 @@ > > > > > no_uaccess_flush > > > > > [PPC] Don't flush the L1-D cache after accessing user data. > > > > > > > > > > + no_virt_spin [RISC-V] Disable virt_spin_lock in KVM guest to use > > > > > + native_queued_spinlock when the nopvspin option is enabled. > > > > > + This would help vcpu=pcpu scenarios. > > > > > + > > > > > novmcoredd [KNL,KDUMP] > > > > > Disable device dump. Device dump allows drivers to > > > > > append dump data to vmcore so you can collect driver > > > > > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h > > > > > index 501e06e52078..e0233b3d7a5f 100644 > > > > > --- a/arch/riscv/include/asm/sbi.h > > > > > +++ b/arch/riscv/include/asm/sbi.h > > > > > @@ -50,6 +50,13 @@ enum sbi_ext_base_fid { > > > > > SBI_EXT_BASE_GET_MIMPID, > > > > > }; > > > > > > > > > > +enum sbi_ext_base_impl_id { > > > > > + SBI_EXT_BASE_IMPL_ID_BBL = 0, > > > > > + SBI_EXT_BASE_IMPL_ID_OPENSBI, > > > > > + SBI_EXT_BASE_IMPL_ID_XVISOR, > > > > > + SBI_EXT_BASE_IMPL_ID_KVM, > > > > > +}; > > > > > + > > > > > enum sbi_ext_time_fid { > > > > > SBI_EXT_TIME_SET_TIMER = 0, > > > > > }; > > > > > @@ -269,6 +276,7 @@ int sbi_console_getchar(void); > > > > > long sbi_get_mvendorid(void); > > > > > long sbi_get_marchid(void); > > > > > long sbi_get_mimpid(void); > > > > > +long sbi_get_firmware_id(void); > > > > > void sbi_set_timer(uint64_t stime_value); > > > > > void sbi_shutdown(void); > > > > > void sbi_send_ipi(unsigned int cpu); > > > > > diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h > > > > > index 8ea0fee80652..6b38d6616f14 100644 > > > > > --- a/arch/riscv/include/asm/spinlock.h > > > > > +++ b/arch/riscv/include/asm/spinlock.h > > > > > @@ -4,6 +4,28 @@ > > > > > #define __ASM_RISCV_SPINLOCK_H > > > > > > > > > > #ifdef CONFIG_QUEUED_SPINLOCKS > > > > > +/* > > > > > + * The KVM guests fall back to a Test-and-Set spinlock, because fair locks > > > > > + * have horrible lock 'holder' preemption issues. The virt_spin_lock_key > > > > > + * would shortcut for the queued_spin_lock_slowpath() function that allow > > > > > + * virt_spin_lock to hijack it. > > > > > + */ > > > > > +DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); > > > > > + > > > > > +#define virt_spin_lock virt_spin_lock > > > > > +static inline bool virt_spin_lock(struct qspinlock *lock) > > > > > +{ > > > > > + if (!static_branch_likely(&virt_spin_lock_key)) > > > > > + return false; > > > > > + > > > > > + do { > > > > > + while (atomic_read(&lock->val) != 0) > > > > > + cpu_relax(); > > > > > + } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0); > > > > > + > > > > > + return true; > > > > > +} > > > > > + > > > > > #define _Q_PENDING_LOOPS (1 << 9) > > > > > #endif > > > > > > > > > > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c > > > > > index 88eea3a99ee0..cdd45edc8db4 100644 > > > > > --- a/arch/riscv/kernel/sbi.c > > > > > +++ b/arch/riscv/kernel/sbi.c > > > > > @@ -555,7 +555,7 @@ static inline long sbi_get_spec_version(void) > > > > > return __sbi_base_ecall(SBI_EXT_BASE_GET_SPEC_VERSION); > > > > > } > > > > > > > > > > -static inline long sbi_get_firmware_id(void) > > > > > +long sbi_get_firmware_id(void) > > > > > { > > > > > return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_ID); > > > > > } > > > > > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c > > > > > index 0f084f037651..c57d15b05160 100644 > > > > > --- a/arch/riscv/kernel/setup.c > > > > > +++ b/arch/riscv/kernel/setup.c > > > > > @@ -26,6 +26,7 @@ > > > > > #include <asm/alternative.h> > > > > > #include <asm/cacheflush.h> > > > > > #include <asm/cpu_ops.h> > > > > > +#include <asm/cpufeature.h> > > > > > #include <asm/early_ioremap.h> > > > > > #include <asm/pgtable.h> > > > > > #include <asm/setup.h> > > > > > @@ -283,16 +284,43 @@ DEFINE_STATIC_KEY_TRUE(combo_qspinlock_key); > > > > > EXPORT_SYMBOL(combo_qspinlock_key); > > > > > #endif > > > > > > > > > > +#ifdef CONFIG_QUEUED_SPINLOCKS > > > > > +static bool no_virt_spin_key = false; > > > > > > > > I suggest no _key, also there is no need for "= false". > > > > To be consistent with enable_qspinlock, I also suggest > > > > adding __ro_after_init: > > > > > > > > static bool no_virt_spin __ro_after_init; > > > okay. > > > > > > > > > > > > > > > > > > > > +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); > > > > > + > > > > > +static int __init no_virt_spin_setup(char *p) > > > > > +{ > > > > > + no_virt_spin_key = true; > > > > > + > > > > > + return 0; > > > > > +} > > > > > +early_param("no_virt_spin", no_virt_spin_setup); > > > > > + > > > > > +static void __init virt_spin_lock_init(void) > > > > > +{ > > > > > + if (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM || > > > > > + no_virt_spin_key) > > > > > + static_branch_disable(&virt_spin_lock_key); > > > > > + else > > > > > + pr_info("Enable virt_spin_lock\n"); > > > > > +} > > > > > +#endif > > > > > + > > > > > > > > A new virt_no_spin kernel parameter was introduced, but without > > > > CONFIG_QUEUED_SPINLOCKS it will silently fail. > > > > > > > > I would suggest an #else clause here with a function to print an error / > > > > warning message about no_virt_spin being invalid in this scenario. > > > > It will probably help future debugging. > > > If CONFIG_QUEUED_SPINLOCKS=n, no_virt_spin should be quiet. The > > > no_virt_spin is one path of qspinlock. > > > > IIUC having no_virt_spin being passed as parameter to a kernel with > > CONFIG_QUEUED_SPINLOCKS=n is not supposed to have any warning this > > parameter is useless. > > > > I was just thinking it would be nice to have this warning during debugging, > > but if it's standard practice then I am ok with this. > Yes, I think it's okay, e.g., > x86: early_param("hv_nopvspin", hv_parse_nopvspin); > depends on CONFIG_PARAVIRT_SPINLOCKS=y Okay then, thanks for sharing this info! > > > > > > > > > > > > > > > > > > > static void __init riscv_spinlock_init(void) > > > > > { > > > > > #ifdef CONFIG_RISCV_COMBO_SPINLOCKS > > > > > - if (!enable_qspinlock_key) { > > > > > + if (!enable_qspinlock_key && > > > > > + (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)) { > > > > > static_branch_disable(&combo_qspinlock_key); > > > > > pr_info("Ticket spinlock: enabled\n"); > > > > > } else { > > > > > pr_info("Queued spinlock: enabled\n"); > > > > > } > > > > > #endif > > > > > + > > > > > +#ifdef CONFIG_QUEUED_SPINLOCKS > > > > > + virt_spin_lock_init(); > > > > > +#endif > > > > > } > > > > > > > > > > extern void __init init_rt_signal_env(void); > > > > > -- > > > > > 2.36.1 > > > > > > > > > > > > > I am probably missing something out, but it looks to me that this patch is > > > > causing 2 different changes: > > > > 1 - Enabling no_virt_spin parameter > > > > 2 - Disabling queued spinlocks for some firmware_id > > > > > > > > Wouldn't be better to split those changes in multiple patches? > > > > Or am I missing the point on why they need to be together? > > > > ^ Want your input on this > Sorry, I missed that. Okay, I would split those changes. Thanks! Leo > > > > > Thanks! > > Leo > > > > > > > > > > Thanks! > > > > Leo > > > > > > > > > > > > > -- > > > Best Regards > > > Guo Ren > > > > > > > > -- > Best Regards > Guo Ren >
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 61cacb8dfd0e..f75bedc50e00 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3927,6 +3927,10 @@ no_uaccess_flush [PPC] Don't flush the L1-D cache after accessing user data. + no_virt_spin [RISC-V] Disable virt_spin_lock in KVM guest to use + native_queued_spinlock when the nopvspin option is enabled. + This would help vcpu=pcpu scenarios. + novmcoredd [KNL,KDUMP] Disable device dump. Device dump allows drivers to append dump data to vmcore so you can collect driver diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h index 501e06e52078..e0233b3d7a5f 100644 --- a/arch/riscv/include/asm/sbi.h +++ b/arch/riscv/include/asm/sbi.h @@ -50,6 +50,13 @@ enum sbi_ext_base_fid { SBI_EXT_BASE_GET_MIMPID, }; +enum sbi_ext_base_impl_id { + SBI_EXT_BASE_IMPL_ID_BBL = 0, + SBI_EXT_BASE_IMPL_ID_OPENSBI, + SBI_EXT_BASE_IMPL_ID_XVISOR, + SBI_EXT_BASE_IMPL_ID_KVM, +}; + enum sbi_ext_time_fid { SBI_EXT_TIME_SET_TIMER = 0, }; @@ -269,6 +276,7 @@ int sbi_console_getchar(void); long sbi_get_mvendorid(void); long sbi_get_marchid(void); long sbi_get_mimpid(void); +long sbi_get_firmware_id(void); void sbi_set_timer(uint64_t stime_value); void sbi_shutdown(void); void sbi_send_ipi(unsigned int cpu); diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h index 8ea0fee80652..6b38d6616f14 100644 --- a/arch/riscv/include/asm/spinlock.h +++ b/arch/riscv/include/asm/spinlock.h @@ -4,6 +4,28 @@ #define __ASM_RISCV_SPINLOCK_H #ifdef CONFIG_QUEUED_SPINLOCKS +/* + * The KVM guests fall back to a Test-and-Set spinlock, because fair locks + * have horrible lock 'holder' preemption issues. The virt_spin_lock_key + * would shortcut for the queued_spin_lock_slowpath() function that allow + * virt_spin_lock to hijack it. + */ +DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key); + +#define virt_spin_lock virt_spin_lock +static inline bool virt_spin_lock(struct qspinlock *lock) +{ + if (!static_branch_likely(&virt_spin_lock_key)) + return false; + + do { + while (atomic_read(&lock->val) != 0) + cpu_relax(); + } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0); + + return true; +} + #define _Q_PENDING_LOOPS (1 << 9) #endif diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c index 88eea3a99ee0..cdd45edc8db4 100644 --- a/arch/riscv/kernel/sbi.c +++ b/arch/riscv/kernel/sbi.c @@ -555,7 +555,7 @@ static inline long sbi_get_spec_version(void) return __sbi_base_ecall(SBI_EXT_BASE_GET_SPEC_VERSION); } -static inline long sbi_get_firmware_id(void) +long sbi_get_firmware_id(void) { return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_ID); } diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c index 0f084f037651..c57d15b05160 100644 --- a/arch/riscv/kernel/setup.c +++ b/arch/riscv/kernel/setup.c @@ -26,6 +26,7 @@ #include <asm/alternative.h> #include <asm/cacheflush.h> #include <asm/cpu_ops.h> +#include <asm/cpufeature.h> #include <asm/early_ioremap.h> #include <asm/pgtable.h> #include <asm/setup.h> @@ -283,16 +284,43 @@ DEFINE_STATIC_KEY_TRUE(combo_qspinlock_key); EXPORT_SYMBOL(combo_qspinlock_key); #endif +#ifdef CONFIG_QUEUED_SPINLOCKS +static bool no_virt_spin_key = false; +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); + +static int __init no_virt_spin_setup(char *p) +{ + no_virt_spin_key = true; + + return 0; +} +early_param("no_virt_spin", no_virt_spin_setup); + +static void __init virt_spin_lock_init(void) +{ + if (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM || + no_virt_spin_key) + static_branch_disable(&virt_spin_lock_key); + else + pr_info("Enable virt_spin_lock\n"); +} +#endif + static void __init riscv_spinlock_init(void) { #ifdef CONFIG_RISCV_COMBO_SPINLOCKS - if (!enable_qspinlock_key) { + if (!enable_qspinlock_key && + (sbi_get_firmware_id() != SBI_EXT_BASE_IMPL_ID_KVM)) { static_branch_disable(&combo_qspinlock_key); pr_info("Ticket spinlock: enabled\n"); } else { pr_info("Queued spinlock: enabled\n"); } #endif + +#ifdef CONFIG_QUEUED_SPINLOCKS + virt_spin_lock_init(); +#endif } extern void __init init_rt_signal_env(void);