| Subject | Re: [PATCH 5.10 119/199] x86/mmx: Use KFPU_387 for MMX string operations | From | Krzysztof Olędzki <> | Date | Mon, 25 Jan 2021 19:24:56 -0800 |
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Hi,
I think for both 5.4-stable and 5.10-stable we also need https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e45122893a9870813f9bd7b4add4f613e6f29008 - "x86/fpu: Add kernel_fpu_begin_mask() to selectively initialize state"
Without this, there is no kernel_fpu_begin_mask().
Thanks, Krzysztof
On 2021-01-25 at 10:39, Greg Kroah-Hartman wrote: > From: Andy Lutomirski <luto@kernel.org> > > commit 67de8dca50c027ca0fa3b62a488ee5035036a0da upstream. > > The default kernel_fpu_begin() doesn't work on systems that support XMM but > haven't yet enabled CR4.OSFXSR. This causes crashes when _mmx_memcpy() is > called too early because LDMXCSR generates #UD when the aforementioned bit > is clear. > > Fix it by using kernel_fpu_begin_mask(KFPU_387) explicitly. > > Fixes: 7ad816762f9b ("x86/fpu: Reset MXCSR to default in kernel_fpu_begin()") > Reported-by: Krzysztof Mazur <krzysiek@podlesie.net> > Signed-off-by: Andy Lutomirski <luto@kernel.org> > Signed-off-by: Borislav Petkov <bp@suse.de> > Tested-by: Krzysztof Piotr Olędzki <ole@ans.pl> > Tested-by: Krzysztof Mazur <krzysiek@podlesie.net> > Cc: <stable@vger.kernel.org> > Link: https://lkml.kernel.org/r/e7bf21855fe99e5f3baa27446e32623358f69e8d.1611205691.git.luto@kernel.org > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > --- > arch/x86/lib/mmx_32.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > --- a/arch/x86/lib/mmx_32.c > +++ b/arch/x86/lib/mmx_32.c > @@ -26,6 +26,16 @@ > #include <asm/fpu/api.h> > #include <asm/asm.h> > > +/* > + * Use KFPU_387. MMX instructions are not affected by MXCSR, > + * but both AMD and Intel documentation states that even integer MMX > + * operations will result in #MF if an exception is pending in FCW. > + * > + * EMMS is not needed afterwards because, after calling kernel_fpu_end(), > + * any subsequent user of the 387 stack will reinitialize it using > + * KFPU_387. > + */ > + > void *_mmx_memcpy(void *to, const void *from, size_t len) > { > void *p; > @@ -37,7 +47,7 @@ void *_mmx_memcpy(void *to, const void * > p = to; > i = len >> 6; /* len/64 */ > > - kernel_fpu_begin(); > + kernel_fpu_begin_mask(KFPU_387); > > __asm__ __volatile__ ( > "1: prefetch (%0)\n" /* This set is 28 bytes */ > @@ -127,7 +137,7 @@ static void fast_clear_page(void *page) > { > int i; > > - kernel_fpu_begin(); > + kernel_fpu_begin_mask(KFPU_387); > > __asm__ __volatile__ ( > " pxor %%mm0, %%mm0\n" : : > @@ -160,7 +170,7 @@ static void fast_copy_page(void *to, voi > { > int i; > > - kernel_fpu_begin(); > + kernel_fpu_begin_mask(KFPU_387); > > /* > * maybe the prefetch stuff can go before the expensive fnsave... > @@ -247,7 +257,7 @@ static void fast_clear_page(void *page) > { > int i; > > - kernel_fpu_begin(); > + kernel_fpu_begin_mask(KFPU_387); > > __asm__ __volatile__ ( > " pxor %%mm0, %%mm0\n" : : > @@ -282,7 +292,7 @@ static void fast_copy_page(void *to, voi > { > int i; > > - kernel_fpu_begin(); > + kernel_fpu_begin_mask(KFPU_387); > > __asm__ __volatile__ ( > "1: prefetch (%0)\n" > >
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