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author | Arnaldo Carvalho de Melo <acme@redhat.com> | 2023-02-06 09:25:56 -0300 |
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committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2023-02-06 09:25:56 -0300 |
commit | ab809efaeba0cca20cfcda23852b0ee958f6ea69 (patch) | |
tree | 36b168deb9908cba8605bb8fa026bdacc26560db /arch/x86/include/asm/debugreg.h | |
parent | 17f248aa8664ff5b3643491136283e73b5c18166 (diff) | |
parent | d2d11f342b179f1894a901f143ec7c008caba43e (diff) | |
download | linux-stable-ab809efaeba0cca20cfcda23852b0ee958f6ea69.tar.gz linux-stable-ab809efaeba0cca20cfcda23852b0ee958f6ea69.tar.bz2 linux-stable-ab809efaeba0cca20cfcda23852b0ee958f6ea69.zip |
Merge remote-tracking branch 'torvalds/master' into perf/core
To sync with libbpf, etc.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'arch/x86/include/asm/debugreg.h')
-rw-r--r-- | arch/x86/include/asm/debugreg.h | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h index b049d950612f..ca97442e8d49 100644 --- a/arch/x86/include/asm/debugreg.h +++ b/arch/x86/include/asm/debugreg.h @@ -39,7 +39,20 @@ static __always_inline unsigned long native_get_debugreg(int regno) asm("mov %%db6, %0" :"=r" (val)); break; case 7: - asm("mov %%db7, %0" :"=r" (val)); + /* + * Apply __FORCE_ORDER to DR7 reads to forbid re-ordering them + * with other code. + * + * This is needed because a DR7 access can cause a #VC exception + * when running under SEV-ES. Taking a #VC exception is not a + * safe thing to do just anywhere in the entry code and + * re-ordering might place the access into an unsafe location. + * + * This happened in the NMI handler, where the DR7 read was + * re-ordered to happen before the call to sev_es_ist_enter(), + * causing stack recursion. + */ + asm volatile("mov %%db7, %0" : "=r" (val) : __FORCE_ORDER); break; default: BUG(); @@ -66,7 +79,16 @@ static __always_inline void native_set_debugreg(int regno, unsigned long value) asm("mov %0, %%db6" ::"r" (value)); break; case 7: - asm("mov %0, %%db7" ::"r" (value)); + /* + * Apply __FORCE_ORDER to DR7 writes to forbid re-ordering them + * with other code. + * + * While is didn't happen with a DR7 write (see the DR7 read + * comment above which explains where it happened), add the + * __FORCE_ORDER here too to avoid similar problems in the + * future. + */ + asm volatile("mov %0, %%db7" ::"r" (value), __FORCE_ORDER); break; default: BUG(); |