Re: [PATCH] x86: Remove 32-bit versions of readq()/writeq()

[Hitoshi Mitake <h.mitake@gmail.com>]

On Fri, May 20, 2011 at 08:54, Roland Dreier <roland@kernel.org> wrote:
> From: Roland Dreier <roland@purestorage.com>
>
> The presense of a writeq() implementation on 32-bit x86 that splits
> the 64-bit write into two 32-bit writes turns out to break the mpt2sas
> driver (and in general is risky for drivers as was discussed in
> <http://lkml.kernel.org/r/adaab6c1h7c.fsf@cisco.com>).  To fix this,
> revert 2c5643b1c5c7 ("x86: provide readq()/writeq() on 32-bit too")
> and follow-on cleanups.
>
> This unfortunately leads to pushing non-atomic definitions of readq()
> and write() to various x86-only drivers that in the mean time started
> using the definitions in the x86 version of <asm/io.h>.  However as
> discussed exhaustively, this is actually the right thing to do,
> because the right way to split a 64-bit transaction is hardware
> dependent and therefore belongs in the hardware driver (eg mpt2sas
> needs a spinlock to make sure no other accesses occur in between the
> two halves of the access).
>
> Build tested on 32- and 64-bit x86 allmodconfig.
>
> Link: http://lkml.kernel.org/r/x86-32-writeq-is-broken@mdm.bga.com
> Cc: Hitoshi Mitake <h.mitake@gmail.com>
> Cc: Kashyap Desai <Kashyap.Desai@lsi.com>
> Cc: Len Brown <lenb@kernel.org>
> Cc: Ravi Anand <ravi.anand@qlogic.com>
> Cc: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
> Cc: Matthew Garrett <mjg@redhat.com>
> Signed-off-by: Roland Dreier <roland@purestorage.com>

I should ack this patch based on the detailed explanation from guys in
the previous thread.
Acked-by: Hitoshi Mitake <h.mitake@gmail.com>

Thanks for your cleaning drivers, Roland!

> ---
>  arch/x86/Kconfig                 |    2 --
>  arch/x86/include/asm/io.h        |   24 ++----------------------
>  drivers/acpi/apei/einj.c         |    8 ++++++++
>  drivers/acpi/atomicio.c          |    4 ++++
>  drivers/edac/i3200_edac.c        |   13 +++++++++++++
>  drivers/platform/x86/ibm_rtl.c   |   13 +++++++++++++
>  drivers/platform/x86/intel_ips.c |   13 +++++++++++++
>  drivers/scsi/qla4xxx/ql4_nx.c    |   21 +++++++++++++++++++++
>  8 files changed, 74 insertions(+), 24 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index cc6c53a..ceb41f3 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -16,8 +16,6 @@ config X86_64
>  config X86
>        def_bool y
>        select HAVE_AOUT if X86_32
> -       select HAVE_READQ
> -       select HAVE_WRITEQ
>        select HAVE_UNSTABLE_SCHED_CLOCK
>        select HAVE_IDE
>        select HAVE_OPROFILE
> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
> index 0722730..d02804d 100644
> --- a/arch/x86/include/asm/io.h
> +++ b/arch/x86/include/asm/io.h
> @@ -38,7 +38,6 @@
>
>  #include <linux/string.h>
>  #include <linux/compiler.h>
> -#include <asm-generic/int-ll64.h>
>  #include <asm/page.h>
>
>  #include <xen/xen.h>
> @@ -87,27 +86,6 @@ build_mmio_write(__writel, "l", unsigned int, "r", )
>  build_mmio_read(readq, "q", unsigned long, "=r", :"memory")
>  build_mmio_write(writeq, "q", unsigned long, "r", :"memory")
>
> -#else
> -
> -static inline __u64 readq(const volatile void __iomem *addr)
> -{
> -       const volatile u32 __iomem *p = addr;
> -       u32 low, high;
> -
> -       low = readl(p);
> -       high = readl(p + 1);
> -
> -       return low + ((u64)high << 32);
> -}
> -
> -static inline void writeq(__u64 val, volatile void __iomem *addr)
> -{
> -       writel(val, addr);
> -       writel(val >> 32, addr+4);
> -}
> -
> -#endif
> -
>  #define readq_relaxed(a)       readq(a)
>
>  #define __raw_readq(a)         readq(a)
> @@ -117,6 +95,8 @@ static inline void writeq(__u64 val, volatile void __iomem *addr)
>  #define readq                  readq
>  #define writeq                 writeq
>
> +#endif
> +
>  /**
>  *     virt_to_phys    -       map virtual addresses to physical
>  *     @address: address to remap
> diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
> index 096aebf..f74b2ea 100644
> --- a/drivers/acpi/apei/einj.c
> +++ b/drivers/acpi/apei/einj.c
> @@ -101,6 +101,14 @@ static DEFINE_MUTEX(einj_mutex);
>
>  static struct einj_parameter *einj_param;
>
> +#ifndef writeq
> +static inline void writeq(__u64 val, volatile void __iomem *addr)
> +{
> +       writel(val, addr);
> +       writel(val >> 32, addr+4);
> +}
> +#endif
> +
>  static void einj_exec_ctx_init(struct apei_exec_context *ctx)
>  {
>        apei_exec_ctx_init(ctx, einj_ins_type, ARRAY_SIZE(einj_ins_type),
> diff --git a/drivers/acpi/atomicio.c b/drivers/acpi/atomicio.c
> index 542e539..7489b89 100644
> --- a/drivers/acpi/atomicio.c
> +++ b/drivers/acpi/atomicio.c
> @@ -280,9 +280,11 @@ static int acpi_atomic_read_mem(u64 paddr, u64 *val, u32 width)
>        case 32:
>                *val = readl(addr);
>                break;
> +#ifdef readq
>        case 64:
>                *val = readq(addr);
>                break;
> +#endif
>        default:
>                return -EINVAL;
>        }
> @@ -307,9 +309,11 @@ static int acpi_atomic_write_mem(u64 paddr, u64 val, u32 width)
>        case 32:
>                writel(val, addr);
>                break;
> +#ifdef writeq
>        case 64:
>                writeq(val, addr);
>                break;
> +#endif
>        default:
>                return -EINVAL;
>        }
> diff --git a/drivers/edac/i3200_edac.c b/drivers/edac/i3200_edac.c
> index d41f900..aa08497 100644
> --- a/drivers/edac/i3200_edac.c
> +++ b/drivers/edac/i3200_edac.c
> @@ -101,6 +101,19 @@ struct i3200_priv {
>
>  static int nr_channels;
>
> +#ifndef readq
> +static inline __u64 readq(const volatile void __iomem *addr)
> +{
> +       const volatile u32 __iomem *p = addr;
> +       u32 low, high;
> +
> +       low = readl(p);
> +       high = readl(p + 1);
> +
> +       return low + ((u64)high << 32);
> +}
> +#endif
> +
>  static int how_many_channels(struct pci_dev *pdev)
>  {
>        unsigned char capid0_8b; /* 8th byte of CAPID0 */
> diff --git a/drivers/platform/x86/ibm_rtl.c b/drivers/platform/x86/ibm_rtl.c
> index 94a114a..b1396e5 100644
> --- a/drivers/platform/x86/ibm_rtl.c
> +++ b/drivers/platform/x86/ibm_rtl.c
> @@ -81,6 +81,19 @@ static void __iomem *rtl_cmd_addr;
>  static u8 rtl_cmd_type;
>  static u8 rtl_cmd_width;
>
> +#ifndef readq
> +static inline __u64 readq(const volatile void __iomem *addr)
> +{
> +       const volatile u32 __iomem *p = addr;
> +       u32 low, high;
> +
> +       low = readl(p);
> +       high = readl(p + 1);
> +
> +       return low + ((u64)high << 32);
> +}
> +#endif
> +
>  static void __iomem *rtl_port_map(phys_addr_t addr, unsigned long len)
>  {
>        if (rtl_cmd_type == RTL_ADDR_TYPE_MMIO)
> diff --git a/drivers/platform/x86/intel_ips.c b/drivers/platform/x86/intel_ips.c
> index 85c8ad4..5ffe7c3 100644
> --- a/drivers/platform/x86/intel_ips.c
> +++ b/drivers/platform/x86/intel_ips.c
> @@ -344,6 +344,19 @@ struct ips_driver {
>  static bool
>  ips_gpu_turbo_enabled(struct ips_driver *ips);
>
> +#ifndef readq
> +static inline __u64 readq(const volatile void __iomem *addr)
> +{
> +       const volatile u32 __iomem *p = addr;
> +       u32 low, high;
> +
> +       low = readl(p);
> +       high = readl(p + 1);
> +
> +       return low + ((u64)high << 32);
> +}
> +#endif
> +
>  /**
>  * ips_cpu_busy - is CPU busy?
>  * @ips: IPS driver struct
> diff --git a/drivers/scsi/qla4xxx/ql4_nx.c b/drivers/scsi/qla4xxx/ql4_nx.c
> index 35381cb..03e522b 100644
> --- a/drivers/scsi/qla4xxx/ql4_nx.c
> +++ b/drivers/scsi/qla4xxx/ql4_nx.c
> @@ -655,6 +655,27 @@ static int qla4_8xxx_pci_is_same_window(struct scsi_qla_host *ha,
>        return 0;
>  }
>
> +#ifndef readq
> +static inline __u64 readq(const volatile void __iomem *addr)
> +{
> +       const volatile u32 __iomem *p = addr;
> +       u32 low, high;
> +
> +       low = readl(p);
> +       high = readl(p + 1);
> +
> +       return low + ((u64)high << 32);
> +}
> +#endif
> +
> +#ifndef writeq
> +static inline void writeq(__u64 val, volatile void __iomem *addr)
> +{
> +       writel(val, addr);
> +       writel(val >> 32, addr+4);
> +}
> +#endif
> +
>  static int qla4_8xxx_pci_mem_read_direct(struct scsi_qla_host *ha,
>                u64 off, void *data, int size)
>  {
>



-- 
Hitoshi Mitake
h.mitake@gmail.com