Hi all,
Today's linux-next merge of the kvm-arm tree got a conflict in:
arch/arm64/include/asm/assembler.h
between commits:
27248fe1abb2 ("arm64: assembler: remove conditional NEON yield macros")
13150149aa6d ("arm64: fpsimd: run kernel mode NEON with softirqs disabled")
from the arm64 tree and commits:
8f4de66e247b ("arm64: asm: Provide set_sctlr_el2 macro")
755db23420a1 ("KVM: arm64: Generate final CTR_EL0 value when running in Protected mode")
from the kvm-arm tree.
I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging. You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.
--
Cheers,
Stephen Rothwell
diff --cc arch/arm64/include/asm/assembler.h
index ab569b0b45fc,34ddd8a0f3dd..000000000000
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@@ -15,7 -15,7 +15,8 @@@
#include <asm-generic/export.h>
#include <asm/asm-offsets.h>
+#include <asm/alternative.h>
+ #include <asm/asm-bug.h>
#include <asm/cpufeature.h>
#include <asm/cputype.h>
#include <asm/debug-monitors.h>
@@@ -701,25 -705,95 +714,33 @@@ USER(\label, ic ivau, \tmp2) // inval
isb
.endm
+ .macro set_sctlr_el1, reg
+ set_sctlr sctlr_el1, \reg
+ .endm
+
+ .macro set_sctlr_el2, reg
+ set_sctlr sctlr_el2, \reg
+ .endm
+
-/*
- * Check whether to yield to another runnable task from kernel mode NEON code
- * (which runs with preemption disabled).
- *
- * if_will_cond_yield_neon
- * // pre-yield patchup code
- * do_cond_yield_neon
- * // post-yield patchup code
- * endif_yield_neon <label>
- *
- * where <label> is optional, and marks the point where execution will resume
- * after a yield has been performed. If omitted, execution resumes right after
- * the endif_yield_neon invocation. Note that the entire sequence, including
- * the provided patchup code, will be omitted from the image if
- * CONFIG_PREEMPTION is not defined.
- *
- * As a convenience, in the case where no patchup code is required, the above
- * sequence may be abbreviated to
- *
- * cond_yield_neon <label>
- *
- * Note that the patchup code does not support assembler directives that change
- * the output section, any use of such directives is undefined.
- *
- * The yield itself consists of the following:
- * - Check whether the preempt count is exactly 1 and a reschedule is also
- * needed. If so, calling of preempt_enable() in kernel_neon_end() will
- * trigger a reschedule. If it is not the case, yielding is pointless.
- * - Disable and re-enable kernel mode NEON, and branch to the yield fixup
- * code.
- *
- * This macro sequence may clobber all CPU state that is not guaranteed by the
- * AAPCS to be preserved across an ordinary function call.
- */
-
- .macro cond_yield_neon, lbl
- if_will_cond_yield_neon
- do_cond_yield_neon
- endif_yield_neon \lbl
- .endm
-
- .macro if_will_cond_yield_neon
-#ifdef CONFIG_PREEMPTION
- get_current_task x0
- ldr x0, [x0, #TSK_TI_PREEMPT]
- sub x0, x0, #PREEMPT_DISABLE_OFFSET
- cbz x0, .Lyield_\@
- /* fall through to endif_yield_neon */
- .subsection 1
-.Lyield_\@ :
-#else
- .section ".discard.cond_yield_neon", "ax"
-#endif
- .endm
-
- .macro do_cond_yield_neon
- bl kernel_neon_end
- bl kernel_neon_begin
- .endm
-
- .macro endif_yield_neon, lbl
- .ifnb \lbl
- b \lbl
- .else
- b .Lyield_out_\@
- .endif
- .previous
-.Lyield_out_\@ :
- .endm
-
/*
- * Check whether preempt-disabled code should yield as soon as it
- * is able. This is the case if re-enabling preemption a single
- * time results in a preempt count of zero, and the TIF_NEED_RESCHED
- * flag is set. (Note that the latter is stored negated in the
- * top word of the thread_info::preempt_count field)
+ * Check whether preempt/bh-disabled asm code should yield as soon as
+ * it is able. This is the case if we are currently running in task
+ * context, and either a softirq is pending, or the TIF_NEED_RESCHED
+ * flag is set and re-enabling preemption a single time would result in
+ * a preempt count of zero. (Note that the TIF_NEED_RESCHED flag is
+ * stored negated in the top word of the thread_info::preempt_count
+ * field)
*/
- .macro cond_yield, lbl:req, tmp:req
-#ifdef CONFIG_PREEMPTION
+ .macro cond_yield, lbl:req, tmp:req, tmp2:req
get_current_task \tmp
ldr \tmp, [\tmp, #TSK_TI_PREEMPT]
+ /*
+ * If we are serving a softirq, there is no point in yielding: the
+ * softirq will not be preempted no matter what we do, so we should
+ * run to completion as quickly as we can.
+ */
+ tbnz \tmp, #SOFTIRQ_SHIFT, .Lnoyield_\@
+#ifdef CONFIG_PREEMPTION
sub \tmp, \tmp, #PREEMPT_DISABLE_OFFSET
cbz \tmp, \lbl
#endif
On Tue, 13 Apr 2021 at 07:43, Stephen Rothwell <[email protected]> wrote:
>
> Hi all,
>
> Today's linux-next merge of the kvm-arm tree got a conflict in:
>
> arch/arm64/include/asm/assembler.h
>
> between commits:
>
> 27248fe1abb2 ("arm64: assembler: remove conditional NEON yield macros")
> 13150149aa6d ("arm64: fpsimd: run kernel mode NEON with softirqs disabled")
>
> from the arm64 tree
Those patches are on a topic branch 'for-next/neon-softirqs-disabled'
in the arm64 tree, so probably best to just pull that into kvm-arm and
fix the conflicts there.
> and commits:
>
> 8f4de66e247b ("arm64: asm: Provide set_sctlr_el2 macro")
> 755db23420a1 ("KVM: arm64: Generate final CTR_EL0 value when running in Protected mode")
>
> from the kvm-arm tree.
>
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging. You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
>
> --
> Cheers,
> Stephen Rothwell
>
> diff --cc arch/arm64/include/asm/assembler.h
> index ab569b0b45fc,34ddd8a0f3dd..000000000000
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@@ -15,7 -15,7 +15,8 @@@
> #include <asm-generic/export.h>
>
> #include <asm/asm-offsets.h>
> +#include <asm/alternative.h>
> + #include <asm/asm-bug.h>
> #include <asm/cpufeature.h>
> #include <asm/cputype.h>
> #include <asm/debug-monitors.h>
> @@@ -701,25 -705,95 +714,33 @@@ USER(\label, ic ivau, \tmp2) // inval
> isb
> .endm
>
> + .macro set_sctlr_el1, reg
> + set_sctlr sctlr_el1, \reg
> + .endm
> +
> + .macro set_sctlr_el2, reg
> + set_sctlr sctlr_el2, \reg
> + .endm
> +
> -/*
> - * Check whether to yield to another runnable task from kernel mode NEON code
> - * (which runs with preemption disabled).
> - *
> - * if_will_cond_yield_neon
> - * // pre-yield patchup code
> - * do_cond_yield_neon
> - * // post-yield patchup code
> - * endif_yield_neon <label>
> - *
> - * where <label> is optional, and marks the point where execution will resume
> - * after a yield has been performed. If omitted, execution resumes right after
> - * the endif_yield_neon invocation. Note that the entire sequence, including
> - * the provided patchup code, will be omitted from the image if
> - * CONFIG_PREEMPTION is not defined.
> - *
> - * As a convenience, in the case where no patchup code is required, the above
> - * sequence may be abbreviated to
> - *
> - * cond_yield_neon <label>
> - *
> - * Note that the patchup code does not support assembler directives that change
> - * the output section, any use of such directives is undefined.
> - *
> - * The yield itself consists of the following:
> - * - Check whether the preempt count is exactly 1 and a reschedule is also
> - * needed. If so, calling of preempt_enable() in kernel_neon_end() will
> - * trigger a reschedule. If it is not the case, yielding is pointless.
> - * - Disable and re-enable kernel mode NEON, and branch to the yield fixup
> - * code.
> - *
> - * This macro sequence may clobber all CPU state that is not guaranteed by the
> - * AAPCS to be preserved across an ordinary function call.
> - */
> -
> - .macro cond_yield_neon, lbl
> - if_will_cond_yield_neon
> - do_cond_yield_neon
> - endif_yield_neon \lbl
> - .endm
> -
> - .macro if_will_cond_yield_neon
> -#ifdef CONFIG_PREEMPTION
> - get_current_task x0
> - ldr x0, [x0, #TSK_TI_PREEMPT]
> - sub x0, x0, #PREEMPT_DISABLE_OFFSET
> - cbz x0, .Lyield_\@
> - /* fall through to endif_yield_neon */
> - .subsection 1
> -.Lyield_\@ :
> -#else
> - .section ".discard.cond_yield_neon", "ax"
> -#endif
> - .endm
> -
> - .macro do_cond_yield_neon
> - bl kernel_neon_end
> - bl kernel_neon_begin
> - .endm
> -
> - .macro endif_yield_neon, lbl
> - .ifnb \lbl
> - b \lbl
> - .else
> - b .Lyield_out_\@
> - .endif
> - .previous
> -.Lyield_out_\@ :
> - .endm
> -
> /*
> - * Check whether preempt-disabled code should yield as soon as it
> - * is able. This is the case if re-enabling preemption a single
> - * time results in a preempt count of zero, and the TIF_NEED_RESCHED
> - * flag is set. (Note that the latter is stored negated in the
> - * top word of the thread_info::preempt_count field)
> + * Check whether preempt/bh-disabled asm code should yield as soon as
> + * it is able. This is the case if we are currently running in task
> + * context, and either a softirq is pending, or the TIF_NEED_RESCHED
> + * flag is set and re-enabling preemption a single time would result in
> + * a preempt count of zero. (Note that the TIF_NEED_RESCHED flag is
> + * stored negated in the top word of the thread_info::preempt_count
> + * field)
> */
> - .macro cond_yield, lbl:req, tmp:req
> -#ifdef CONFIG_PREEMPTION
> + .macro cond_yield, lbl:req, tmp:req, tmp2:req
> get_current_task \tmp
> ldr \tmp, [\tmp, #TSK_TI_PREEMPT]
> + /*
> + * If we are serving a softirq, there is no point in yielding: the
> + * softirq will not be preempted no matter what we do, so we should
> + * run to completion as quickly as we can.
> + */
> + tbnz \tmp, #SOFTIRQ_SHIFT, .Lnoyield_\@
> +#ifdef CONFIG_PREEMPTION
> sub \tmp, \tmp, #PREEMPT_DISABLE_OFFSET
> cbz \tmp, \lbl
> #endif