| Message ID | 20151027154424.GG1689@arm.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Oct 27, 2015 at 03:44:24PM +0000, Will Deacon wrote: > On Fri, Oct 16, 2015 at 11:37:29AM +0100, Catalin Marinas wrote: > > On Fri, Oct 16, 2015 at 08:52:24AM +0100, Vladimir Murzin wrote: > > > > On 15/10/15 14:02, Will Deacon wrote: > > > >> diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c > > > >> index bcee7abac68e..6039d1eb5912 100644 > > > >> --- a/arch/arm64/kernel/armv8_deprecated.c > > > >> +++ b/arch/arm64/kernel/armv8_deprecated.c > > > >> @@ -284,12 +284,12 @@ static void register_insn_emulation_sysctl(struct ctl_table *table) > > > >> __asm__ __volatile__( \ > > > >> ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \ > > > >> CONFIG_ARM64_PAN) \ > > > >> - " mov %w2, %w1\n" \ > > > >> - "0: ldxr"B" %w1, [%3]\n" \ > > > >> - "1: stxr"B" %w0, %w2, [%3]\n" \ > > > >> + "0: ldxr"B" %w2, [%3]\n" \ > > > >> + "1: stxr"B" %w0, %w1, [%3]\n" \ > > > >> " cbz %w0, 2f\n" \ > > > >> " mov %w0, %w4\n" \ > > > >> "2:\n" \ > > > >> + " mov %w1, %w2\n" \ > > > >> " .pushsection .fixup,\"ax\"\n" \ > > > >> " .align 2\n" \ > > > >> "3: mov %w0, %w5\n" \ > > > > > > On the second thought looks like we still update *data in case stxr > > > fails (or I need more coffee). > > > > I'm on the second cup and I see the same problem. Even if stxr fails, we > > fall back through "mov %w1, %w2", so *data is always updated with the > > loaded value. Maybe something like below on top of Will's patch: > > Yeah, sorry, my original patch was an untested mess. I think we can avoid > the "cc" clobber by adding a branch to the slow-path, as below. > > Still needs testing, mind. Right, it passes the simple test case I wrote (which fails under mainline). Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c index 6039d1eb5912..937f5e58a4d3 100644 --- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -288,17 +288,19 @@ static void register_insn_emulation_sysctl(struct ctl_table *table) "1: stxr"B" %w0, %w1, [%3]\n" \ " cbz %w0, 2f\n" \ " mov %w0, %w4\n" \ + " b 3f\n" \ "2:\n" \ " mov %w1, %w2\n" \ + "3:\n" \ " .pushsection .fixup,\"ax\"\n" \ " .align 2\n" \ - "3: mov %w0, %w5\n" \ - " b 2b\n" \ + "4: mov %w0, %w5\n" \ + " b 3b\n" \ " .popsection" \ " .pushsection __ex_table,\"a\"\n" \ " .align 3\n" \ - " .quad 0b, 3b\n" \ - " .quad 1b, 3b\n" \ + " .quad 0b, 4b\n" \ + " .quad 1b, 4b\n" \ " .popsection\n" \ ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, \ CONFIG_ARM64_PAN) \