| Message ID | 20210125183203.376765980@linuxfoundation.org |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
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> Similar to 5.10.11, we also need https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e45122893a9870813f9bd7b4add4f613e6f29008 in 5.4.93: Otherwise, the kernel will fail to compile if CONFIG_X86_USE_3DNOW=y arch/x86/lib/mmx_32.c: In function '_mmx_memcpy': arch/x86/lib/mmx_32.c:50:2: error: implicit declaration of function 'kernel_fpu_begin_mask'; did you mean 'kernel_fpu_begin'? [-Werror=implicit-function-declaration] 50 | kernel_fpu_begin_mask(KFPU_387); | ^~~~~~~~~~~~~~~~~~~~~ | kernel_fpu_begin arch/x86/lib/mmx_32.c:50:24: error: 'KFPU_387' undeclared (first use in this function) 50 | kernel_fpu_begin_mask(KFPU_387); | ^~~~~~~~ arch/x86/lib/mmx_32.c:50:24: note: each undeclared identifier is reported only once for each function it appears in arch/x86/lib/mmx_32.c: In function 'fast_clear_page': arch/x86/lib/mmx_32.c:140:24: error: 'KFPU_387' undeclared (first use in this function) 140 | kernel_fpu_begin_mask(KFPU_387); | ^~~~~~~~ arch/x86/lib/mmx_32.c: In function 'fast_copy_page': arch/x86/lib/mmx_32.c:173:24: error: 'KFPU_387' undeclared (first use in this function) 173 | kernel_fpu_begin_mask(KFPU_387); | ^~~~~~~~ Thanks, Krzysztof
--- 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"