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um: Enable preemption in UML

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Since userspace state is saved in the MM process, kernel using
FPU still doesn't really need to do anything, so this really
is as simple as enabling preemption. The irq critical section
in sigio_handler() needs preempt_disable()/preempt_enable().

Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Link: https://patch.msgid.link/20240702102549.d2fcea450854.I12f5a53d80ec1e425e66ef272b1e95cb523b608e@changeid
[rebase, remove FPU save/restore, fix x86/um Makefile,
 rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Anton Ivanov 2024-07-02 10:25:50 +02:00 committed by Johannes Berg
parent bcf3d957c6
commit cd01672d64
3 changed files with 3 additions and 2 deletions
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2
arch/um/Kconfig
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@ -11,7 +11,7 @@ config UML
select ARCH_HAS_KCOV
select ARCH_HAS_STRNCPY_FROM_USER
select ARCH_HAS_STRNLEN_USER
select ARCH_NO_PREEMPT
select ARCH_NO_PREEMPT_DYNAMIC
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_KASAN if X86_64
select HAVE_ARCH_KASAN_VMALLOC if HAVE_ARCH_KASAN

2
arch/um/kernel/irq.c
View File

@ -238,7 +238,9 @@ static void _sigio_handler(struct uml_pt_regs *regs,
void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
{
preempt_disable();
_sigio_handler(regs, irqs_suspended);
preempt_enable();
}
static struct irq_entry *get_irq_entry_by_fd(int fd)

1
arch/x86/um/Makefile
View File

@ -31,7 +31,6 @@ obj-y += syscalls_64.o vdso/
subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o \
../lib/memmove_64.o ../lib/memset_64.o
subarch-$(CONFIG_PREEMPTION) += ../entry/thunk_64.o
endif