From: Mark Brown <broonie@kernel.org>
To: kbuild-all@lists.01.org
Subject: Re: arch/arm64/kernel/fpsimd.c:1944:55: sparse: sparse: dereference of noderef expression
Date: Thu, 02 Jun 2022 10:22:52 +0200 [thread overview]
Message-ID: <YphzXEcBKARluNVM@sirena.org.uk> (raw)
In-Reply-To: <YpeZ0M5we/0yzxVC@arm.com>
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On Wed, Jun 01, 2022 at 05:54:40PM +0100, Catalin Marinas wrote:
> On Wed, Jun 01, 2022 at 09:50:39AM +0200, Mark Brown wrote:
> > On Tue, May 31, 2022 at 05:57:42PM +0100, Catalin Marinas wrote:
> > Yes, that looks right - feel free to add my Reviewed-by or I'll
> > do that when I see the patch sent properly.
> I'm no longer convinced that's the right fix. In __efi_fpsimd_begin(),
> ffr is true if either !system_supports_fa64() or SVCR.SM is set. The FFR
> state would be saved in this case.
That's the wrong way round - we should only save FFR if we have
FA64 or SVCR.SM is *not* set. Checking again efi_fpsimd_begin()
is wrong.
> In __efi_fpsimd_end(), shouldn't we just restore the FFR state if
> efi_sm_state, irrespective of system_supports_fa64() (as it was checked
> in the beginning). Something like:
No, we should restore it only if we saved it. The below should
resolve things but it's completely untested:
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 819979398127..3c66a061ff6f 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1916,10 +1916,11 @@ void __efi_fpsimd_begin(void)
if (system_supports_sme()) {
svcr = read_sysreg_s(SYS_SVCR);
- if (!system_supports_fa64())
- ffr = svcr & SVCR_SM_MASK;
+ __this_cpu_write(efi_sm_state,
+ svcr & SVCR_SM_MASK);
- __this_cpu_write(efi_sm_state, ffr);
+ if (!system_supports_fa64())
+ ffr = !(svcr & SVCR_SM_MASK);
}
sve_save_state(sve_state + sve_ffr_offset(sve_max_vl()),
@@ -1965,7 +1966,7 @@ void __efi_fpsimd_end(void)
0,
SVCR_SM_MASK);
if (!system_supports_fa64())
- ffr = efi_sm_state;
+ ffr = false;
}
}
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WARNING: multiple messages have this Message-ID (diff)
From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: kernel test robot <lkp@intel.com>,
kbuild-all@lists.01.org, linux-kernel@vger.kernel.org
Subject: Re: arch/arm64/kernel/fpsimd.c:1944:55: sparse: sparse: dereference of noderef expression
Date: Thu, 2 Jun 2022 10:22:52 +0200 [thread overview]
Message-ID: <YphzXEcBKARluNVM@sirena.org.uk> (raw)
In-Reply-To: <YpeZ0M5we/0yzxVC@arm.com>
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On Wed, Jun 01, 2022 at 05:54:40PM +0100, Catalin Marinas wrote:
> On Wed, Jun 01, 2022 at 09:50:39AM +0200, Mark Brown wrote:
> > On Tue, May 31, 2022 at 05:57:42PM +0100, Catalin Marinas wrote:
> > Yes, that looks right - feel free to add my Reviewed-by or I'll
> > do that when I see the patch sent properly.
> I'm no longer convinced that's the right fix. In __efi_fpsimd_begin(),
> ffr is true if either !system_supports_fa64() or SVCR.SM is set. The FFR
> state would be saved in this case.
That's the wrong way round - we should only save FFR if we have
FA64 or SVCR.SM is *not* set. Checking again efi_fpsimd_begin()
is wrong.
> In __efi_fpsimd_end(), shouldn't we just restore the FFR state if
> efi_sm_state, irrespective of system_supports_fa64() (as it was checked
> in the beginning). Something like:
No, we should restore it only if we saved it. The below should
resolve things but it's completely untested:
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 819979398127..3c66a061ff6f 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1916,10 +1916,11 @@ void __efi_fpsimd_begin(void)
if (system_supports_sme()) {
svcr = read_sysreg_s(SYS_SVCR);
- if (!system_supports_fa64())
- ffr = svcr & SVCR_SM_MASK;
+ __this_cpu_write(efi_sm_state,
+ svcr & SVCR_SM_MASK);
- __this_cpu_write(efi_sm_state, ffr);
+ if (!system_supports_fa64())
+ ffr = !(svcr & SVCR_SM_MASK);
}
sve_save_state(sve_state + sve_ffr_offset(sve_max_vl()),
@@ -1965,7 +1966,7 @@ void __efi_fpsimd_end(void)
0,
SVCR_SM_MASK);
if (!system_supports_fa64())
- ffr = efi_sm_state;
+ ffr = false;
}
}
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next prev parent reply other threads:[~2022-06-02 8:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-27 22:49 arch/arm64/kernel/fpsimd.c:1944:55: sparse: sparse: dereference of noderef expression kernel test robot
2022-05-31 16:57 ` Catalin Marinas
2022-05-31 16:57 ` Catalin Marinas
2022-06-01 7:50 ` Mark Brown
2022-06-01 7:50 ` Mark Brown
2022-06-01 16:54 ` Catalin Marinas
2022-06-01 16:54 ` Catalin Marinas
2022-06-02 8:22 ` Mark Brown [this message]
2022-06-02 8:22 ` Mark Brown
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