| Message ID | 1423722898-16110-2-git-send-email-julien.grall@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 2015-02-12 at 06:34 +0000, Julien Grall wrote: > The function irq_of_parse_and_map returns 0 when the IRQ is not found. > > Furthermore xen_events_irq is only read when the CPU is bring up, so > it's not necessary to use the attribute __read_mostly. Part of the purpose of __read_mostly is to move such things out of sharing cachelines with other more hot read/write things, as much as it is to group all the "read only" things together.
Hi Ian, On 18/02/2015 11:27, Ian Campbell wrote: > On Thu, 2015-02-12 at 06:34 +0000, Julien Grall wrote: >> The function irq_of_parse_and_map returns 0 when the IRQ is not found. >> >> Furthermore xen_events_irq is only read when the CPU is bring up, so >> it's not necessary to use the attribute __read_mostly. > > Part of the purpose of __read_mostly is to move such things out of > sharing cachelines with other more hot read/write things, as much as it > is to group all the "read only" things together. Hmmm... You are right. I didn't understand this macro like that. I will resend the series with this patch drop and add Ard's patch [1]. Regards, [1] https://patches.linaro.org/44633/
On 18/02/2015 11:41, Julien Grall wrote: > Hi Ian, > > On 18/02/2015 11:27, Ian Campbell wrote: >> On Thu, 2015-02-12 at 06:34 +0000, Julien Grall wrote: >>> The function irq_of_parse_and_map returns 0 when the IRQ is not found. >>> >>> Furthermore xen_events_irq is only read when the CPU is bring up, so >>> it's not necessary to use the attribute __read_mostly. >> >> Part of the purpose of __read_mostly is to move such things out of >> sharing cachelines with other more hot read/write things, as much as it >> is to group all the "read only" things together. > > Hmmm... You are right. I didn't understand this macro like that. > > I will resend the series with this patch drop and add Ard's patch [1]. Actually I'm stupid... This patch is still useful except the __read_mostly. > > Regards, > > [1] https://patches.linaro.org/44633/ >
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c index 263a204..90101c8 100644 --- a/arch/arm/xen/enlighten.c +++ b/arch/arm/xen/enlighten.c @@ -51,7 +51,7 @@ EXPORT_SYMBOL_GPL(xen_have_vector_callback); int xen_platform_pci_unplug = XEN_UNPLUG_ALL; EXPORT_SYMBOL_GPL(xen_platform_pci_unplug); -static __read_mostly int xen_events_irq = -1; +static unsigned int xen_events_irq; /* map fgmfn of domid to lpfn in the current domain */ static int map_foreign_page(unsigned long lpfn, unsigned long fgmfn, @@ -251,12 +251,14 @@ static int __init xen_guest_init(void) return 0; grant_frames = res.start; xen_events_irq = irq_of_parse_and_map(node, 0); + if (!xen_events_irq) { + pr_debug("Xen event channel interrupt not found\n"); + return -ENODEV; + } + pr_info("Xen %s support found, events_irq=%d gnttab_frame=%pa\n", version, xen_events_irq, &grant_frames); - if (xen_events_irq < 0) - return -ENODEV; - xen_domain_type = XEN_HVM_DOMAIN; xen_setup_features();
The function irq_of_parse_and_map returns 0 when the IRQ is not found. Furthermore xen_events_irq is only read when the CPU is bring up, so it's not necessary to use the attribute __read_mostly. Lastly, move the check before notifying the user that we are running on Xen. Signed-off-by: Julien Grall <julien.grall@linaro.org> --- arch/arm/xen/enlighten.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)