From: "Michal Suchánek" <msuchanek@suse•de>
To: Nicholas Piggin <npiggin@gmail•com>
Cc: Tulio Magno Quites Machado Filho <tuliom@linux•ibm.com>,
linuxppc-dev@lists•ozlabs.org
Subject: Re: [RFC PATCH 27/27] powerpc/64s: system call support for scv/rfscv instructions
Date: Wed, 2 Oct 2019 10:21:09 +0200 [thread overview]
Message-ID: <20190923125046.GD18205@kitsune.suse.cz> (raw)
In-Reply-To: <20190915012813.29317-28-npiggin@gmail.com>
On Sun, Sep 15, 2019 at 11:28:13AM +1000, Nicholas Piggin wrote:
> Add support for the scv instruction on POWER9 and later CPUs.
>
> For now this implements the zeroth scv vector 'scv 0', as identical
> to 'sc' system calls, with the exception that lr is not preserved, and
> it is 64-bit only. There may yet be changes made to this ABI, so it's
> for testing only.
>
> This also doesn't yet properly handle PR KVM, or the case where a guest
> is denied AIL=3 mode. I haven't added real mode entry points, so scv
> must not be used when AIL=0, but I haven't cleared the FSCR in this
> case.
>
> This also implements a strange hack to handle the non-implemented
> vectors, scheduling a decrementer and expecting it to interrupt and
> replay pending soft masked interrupts. This is unlikely to be a good
> idea, and needs to actually do a proper handler and replay in case an
> interrupt is pending.
>
> It may also require some errata handling before it can be safely used
> on all POWER9 CPUs, I have to look that up.
>
> rfscv is implemented to return from scv type system calls. It can not
> be used to return from sc system calls because those are defined to
> preserve lr.
>
> In a comparison of getpid syscall, the test program had scv taking
> about 3 more cycles in user mode (92 vs 89 for sc), due to lr handling.
> Total cycles taken for a getpid system call on POWER9 are improved from
> 436 to 345 (26.3% faster), mostly due to reducing mtmsr and mtspr.
...
> diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
> index 034b52d3d78c..3e8aa5ae8ec8 100644
> --- a/arch/powerpc/kernel/syscall_64.c
> +++ b/arch/powerpc/kernel/syscall_64.c
> @@ -15,6 +15,77 @@ extern void __noreturn tabort_syscall(void);
>
> typedef long (*syscall_fn)(long, long, long, long, long, long);
>
> +#ifdef CONFIG_PPC_BOOK3S
> +long system_call_vectored_exception(long r3, long r4, long r5, long r6, long r7, long r8, unsigned long r0, struct pt_regs *regs)
> +{
> + unsigned long ti_flags;
> + syscall_fn f;
> +
> + BUG_ON(!(regs->msr & MSR_RI));
> + BUG_ON(!(regs->msr & MSR_PR));
> + BUG_ON(!FULL_REGS(regs));
> + BUG_ON(regs->softe != IRQS_ENABLED);
> +
> + if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
> + unlikely(regs->msr & MSR_TS_T))
> + tabort_syscall();
> +
> + account_cpu_user_entry();
> +
> +#ifdef CONFIG_PPC_SPLPAR
> + if (IS_ENABLED(CONFIG_VIRT_CPU_ACCOUNTING_NATIVE) &&
> + firmware_has_feature(FW_FEATURE_SPLPAR)) {
> + struct lppaca *lp = get_lppaca();
> +
> + if (unlikely(local_paca->dtl_ridx != lp->dtl_idx))
This adds another instance of the lack of endian conversion issue.
> + accumulate_stolen_time();
> + }
> +#endif
Thanks
Michal
next prev parent reply other threads:[~2019-10-02 8:26 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-15 1:27 [RFC PATCH 00/27] current interrupt series plus scv syscall Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 01/27] powerpc/64s/exception: Introduce INT_DEFINE parameter block for code generation Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 02/27] powerpc/64s/exception: Add GEN_COMMON macro that uses INT_DEFINE parameters Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 03/27] powerpc/64s/exception: Add GEN_KVM " Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 04/27] powerpc/64s/exception: Expand EXC_COMMON and EXC_COMMON_ASYNC macros Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 05/27] powerpc/64s/exception: Move all interrupt handlers to new style code gen macros Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 06/27] powerpc/64s/exception: Remove old INT_ENTRY macro Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 07/27] powerpc/64s/exception: Remove old INT_COMMON macro Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 08/27] powerpc/64s/exception: Remove old INT_KVM_HANDLER Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 09/27] powerpc/64s/exception: Add ISIDE option Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 10/27] powerpc/64s/exception: move real->virt switch into the common handler Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 11/27] powerpc/64s/exception: move soft-mask test to common code Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 12/27] powerpc/64s/exception: move KVM " Nicholas Piggin
2019-09-15 1:27 ` [RFC PATCH 13/27] powerpc/64s/exception: remove confusing IEARLY option Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 14/27] powerpc/64s/exception: remove the SPR saving patch code macros Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 15/27] powerpc/64s/exception: trim unused arguments from KVMTEST macro Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 16/27] powerpc/64s/exception: hdecrementer avoid touching the stack Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 17/27] powerpc/64s/exception: re-inline some handlers Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 18/27] powerpc/64s/exception: Clean up SRR specifiers Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 19/27] powerpc/64s/exception: add more comments for interrupt handlers Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 20/27] powerpc/64s/exception: only test KVM in SRR interrupts when PR KVM is supported Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 21/27] powerpc/64s/exception: soft nmi interrupt should not use ret_from_except Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 22/27] powerpc/64: system call remove non-volatile GPR save optimisation Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 23/27] powerpc/64: system call implement the bulk of the logic in C Nicholas Piggin
2019-10-02 8:21 ` Michal Suchánek
2019-10-02 3:10 ` Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 24/27] powerpc/64s: interrupt return " Nicholas Piggin
2019-10-02 8:20 ` Michal Suchánek
2019-09-15 1:28 ` [RFC PATCH 25/27] powerpc/64s/exception: remove lite interrupt return Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 26/27] powerpc/64s/exception: treat NIA below __end_interrupts as soft-masked Nicholas Piggin
2019-09-15 1:28 ` [RFC PATCH 27/27] powerpc/64s: system call support for scv/rfscv instructions Nicholas Piggin
2019-10-02 8:21 ` Michal Suchánek [this message]
2019-10-02 8:20 ` [RFC PATCH 00/27] current interrupt series plus scv syscall Michal Suchánek
2019-10-02 3:13 ` Nicholas Piggin
2019-10-30 12:55 ` Michal Suchánek
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