Re: [PATCH v3 03/18] x86/tsc/paravirt: Remove the read_tsc and read_tscp paravirt hooks

Borislav Petkov
2015-06-17T09:56:34Z

+ paravirt list.

On Tue, Jun 16, 2015 at 05:35:51PM -0700, Andy Lutomirski wrote:
> We've had read_tsc and read_tscp paravirt hooks since the very
> beginning of paravirt, i.e., d3561b7fa0fb ("[PATCH] paravirt: header
> and stubs for paravirtualisation"). AFAICT the only paravirt guest
> implementation that ever replaced these calls was vmware, and it's
> gone. Arguably even vmware shouldn't have hooked rdtsc -- we fully
> support systems that don't have a TSC at all, so there's no point
> for a paravirt implementation to pretend that we have a TSC but to
> replace it.
>
> I also doubt that these hooks actually worked. Calls to rdtscl and
> rdtscll, which respected the hooks, were used seemingly
> interchangeably with native_read_tsc, which did not.
>
> Just remove them. If anyone ever needs them again, they can try
> to make a case for why they need them.
>
> Before, on a paravirt config:
> text data bss dec hex filename
> 13426505 1827056 14508032 29761593 1c62039 vmlinux
>
> After:
> text data bss dec hex filename
> 13426617 1827056 14508032 29761705 1c620a9 vmlinux
>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/include/asm/msr.h | 16 ++++++++--------
> arch/x86/include/asm/paravirt.h | 34 ----------------------------------
> arch/x86/include/asm/paravirt_types.h | 2 --
> arch/x86/kernel/paravirt.c | 2 --
> arch/x86/kernel/paravirt_patch_32.c | 2 --
> arch/x86/xen/enlighten.c | 3 ---
> 6 files changed, 8 insertions(+), 51 deletions(-)

Nice diffstat.

Acked-by: Borislav Petkov <bp@suse.de>

(leaving in the rest for reference)

> diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
> index 88711470af7f..d1afac7df484 100644
> --- a/arch/x86/include/asm/msr.h
> +++ b/arch/x86/include/asm/msr.h
> @@ -178,12 +178,6 @@ static inline int rdmsrl_safe(unsigned msr, unsigned long long *p)
> return err;
> }
>
> -#define rdtscl(low) \
> - ((low) = (u32)native_read_tsc())
> -
> -#define rdtscll(val) \
> - ((val) = native_read_tsc())
> -
> #define rdpmc(counter, low, high) \
> do { \
> u64 _l = native_read_pmc((counter)); \
> @@ -193,6 +187,14 @@ do { \
>
> #define rdpmcl(counter, val) ((val) = native_read_pmc(counter))
>
> +#endif /* !CONFIG_PARAVIRT */
> +
> +#define rdtscl(low) \
> + ((low) = (u32)native_read_tsc())
> +
> +#define rdtscll(val) \
> + ((val) = native_read_tsc())
> +
> #define rdtscp(low, high, aux) \
> do { \
> unsigned long long _val = native_read_tscp(&(aux)); \
> @@ -202,8 +204,6 @@ do { \
>
> #define rdtscpll(val, aux) (val) = native_read_tscp(&(aux))
>
> -#endif /* !CONFIG_PARAVIRT */
> -
> /*
> * 64-bit version of wrmsr_safe():
> */
> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
> index d143bfad45d7..c2be0375bcad 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -174,19 +174,6 @@ static inline int rdmsrl_safe(unsigned msr, unsigned long long *p)
> return err;
> }
>
> -static inline u64 paravirt_read_tsc(void)
> -{
> - return PVOP_CALL0(u64, pv_cpu_ops.read_tsc);
> -}
> -
> -#define rdtscl(low) \
> -do { \
> - u64 _l = paravirt_read_tsc(); \
> - low = (int)_l; \
> -} while (0)
> -
> -#define rdtscll(val) (val = paravirt_read_tsc())
> -
> static inline unsigned long long paravirt_sched_clock(void)
> {
> return PVOP_CALL0(unsigned long long, pv_time_ops.sched_clock);
> @@ -215,27 +202,6 @@ do { \
>
> #define rdpmcl(counter, val) ((val) = paravirt_read_pmc(counter))
>
> -static inline unsigned long long paravirt_rdtscp(unsigned int *aux)
> -{
> - return PVOP_CALL1(u64, pv_cpu_ops.read_tscp, aux);
> -}
> -
> -#define rdtscp(low, high, aux) \
> -do { \
> - int __aux; \
> - unsigned long __val = paravirt_rdtscp(&__aux); \
> - (low) = (u32)__val; \
> - (high) = (u32)(__val >> 32); \
> - (aux) = __aux; \
> -} while (0)
> -
> -#define rdtscpll(val, aux) \
> -do { \
> - unsigned long __aux; \
> - val = paravirt_rdtscp(&__aux); \
> - (aux) = __aux; \
> -} while (0)
> -
> static inline void paravirt_alloc_ldt(struct desc_struct *ldt, unsigned entries)
> {
> PVOP_VCALL2(pv_cpu_ops.alloc_ldt, ldt, entries);
> diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
> index a6b8f9fadb06..ce029e4fa7c6 100644
> --- a/arch/x86/include/asm/paravirt_types.h
> +++ b/arch/x86/include/asm/paravirt_types.h
> @@ -156,9 +156,7 @@ struct pv_cpu_ops {
> u64 (*read_msr)(unsigned int msr, int *err);
> int (*write_msr)(unsigned int msr, unsigned low, unsigned high);
>
> - u64 (*read_tsc)(void);
> u64 (*read_pmc)(int counter);
> - unsigned long long (*read_tscp)(unsigned int *aux);
>
> #ifdef CONFIG_X86_32
> /*
> diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
> index 58bcfb67c01f..f68e48f5f6c2 100644
> --- a/arch/x86/kernel/paravirt.c
> +++ b/arch/x86/kernel/paravirt.c
> @@ -351,9 +351,7 @@ __visible struct pv_cpu_ops pv_cpu_ops = {
> .wbinvd = native_wbinvd,
> .read_msr = native_read_msr_safe,
> .write_msr = native_write_msr_safe,
> - .read_tsc = native_read_tsc,
> .read_pmc = native_read_pmc,
> - .read_tscp = native_read_tscp,
> .load_tr_desc = native_load_tr_desc,
> .set_ldt = native_set_ldt,
> .load_gdt = native_load_gdt,
> diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c
> index e1b013696dde..c89f50a76e97 100644
> --- a/arch/x86/kernel/paravirt_patch_32.c
> +++ b/arch/x86/kernel/paravirt_patch_32.c
> @@ -10,7 +10,6 @@ DEF_NATIVE(pv_mmu_ops, read_cr2, "mov %cr2, %eax");
> DEF_NATIVE(pv_mmu_ops, write_cr3, "mov %eax, %cr3");
> DEF_NATIVE(pv_mmu_ops, read_cr3, "mov %cr3, %eax");
> DEF_NATIVE(pv_cpu_ops, clts, "clts");
> -DEF_NATIVE(pv_cpu_ops, read_tsc, "rdtsc");
>
> #if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS)
> DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%eax)");
> @@ -52,7 +51,6 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
> PATCH_SITE(pv_mmu_ops, read_cr3);
> PATCH_SITE(pv_mmu_ops, write_cr3);
> PATCH_SITE(pv_cpu_ops, clts);
> - PATCH_SITE(pv_cpu_ops, read_tsc);
> #if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS)
> case PARAVIRT_PATCH(pv_lock_ops.queued_spin_unlock):
> if (pv_is_native_spin_unlock()) {
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 0b95c9b8283f..32136bfca43f 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1175,11 +1175,8 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
> .read_msr = xen_read_msr_safe,
> .write_msr = xen_write_msr_safe,
>
> - .read_tsc = native_read_tsc,
> .read_pmc = native_read_pmc,
>
> - .read_tscp = native_read_tscp,
> -
> .iret = xen_iret,
> #ifdef CONFIG_X86_64
> .usergs_sysret32 = xen_sysret32,
> --
> 2.4.2
>

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
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