From 4efb1ca7d2a44cfb33d7f9e18bd92f8d68dcfee0 Mon Sep 17 00:00:00 2001 From: Brandon Bergren Date: Wed, 23 Sep 2020 00:09:29 +0000 Subject: [PATCH] [PowerPC64LE] Work around qemu TCG bug in mtmsrd emulation. The TCG implementation of mtmsrd in qemu blindly copies the entire register to the MSR, instead of the specific bit positions listed in the ISA. This means that qemu will prematurely switch endian out from under the running code instead of waiting for the rfid, causing an immediate trap as it attempts to interpret the next instruction in the wrong endianness. To work around this, ensure PSL_LE is still set before doing the mtmsrd. In the future, we may wish to just turn off translation and unconditionally use rfid to switch to the ofmsr instead of quasi-switching to the ofmsr. Add a new platform option so this can be disabled. (And so that we can conditonalize additional QEMU-specific hacks in the platform code.) Sponsored by: Tag1 Consulting, Inc. --- sys/conf/options.powerpc | 1 + sys/powerpc/conf/GENERIC64 | 1 + sys/powerpc/conf/NOTES | 1 + sys/powerpc/ofw/ofwcall64.S | 10 ++++++++++ sys/powerpc/powernv/opalcall.S | 11 +++++++++++ 5 files changed, 24 insertions(+) diff --git a/sys/conf/options.powerpc b/sys/conf/options.powerpc index 6e9eb81ecaf..1a22f931450 100644 --- a/sys/conf/options.powerpc +++ b/sys/conf/options.powerpc @@ -29,6 +29,7 @@ MAMBO POWERNV opt_platform.h PSERIES PSIM +QEMU opt_platform.h SC_OFWFB opt_ofwfb.h diff --git a/sys/powerpc/conf/GENERIC64 b/sys/powerpc/conf/GENERIC64 index a70cd0db605..18eedb7f927 100644 --- a/sys/powerpc/conf/GENERIC64 +++ b/sys/powerpc/conf/GENERIC64 @@ -30,6 +30,7 @@ makeoptions WITH_CTF=1 options POWERMAC #NewWorld Apple PowerMacs options PS3 #Sony Playstation 3 options MAMBO #IBM Mambo Full System Simulator +options QEMU #QEMU processor emulator options PSERIES #PAPR-compliant systems (e.g. IBM p) options POWERNV #Non-virtualized OpenPOWER systems diff --git a/sys/powerpc/conf/NOTES b/sys/powerpc/conf/NOTES index 74a03f2cedc..c41a0a61184 100644 --- a/sys/powerpc/conf/NOTES +++ b/sys/powerpc/conf/NOTES @@ -44,6 +44,7 @@ options POWERMAC #NewWorld Apple PowerMacs #options PS3 #Sony Playstation 3 options PSIM #GDB PSIM ppc simulator options MAMBO #IBM Mambo Full System Simulator +options QEMU #QEMU processor emulator # The cpufreq(4) driver provides support for CPU frequency control device cpufreq diff --git a/sys/powerpc/ofw/ofwcall64.S b/sys/powerpc/ofw/ofwcall64.S index 481c109affd..3230cdf79c3 100644 --- a/sys/powerpc/ofw/ofwcall64.S +++ b/sys/powerpc/ofw/ofwcall64.S @@ -32,6 +32,8 @@ #include #include +#include "opt_platform.h" + #define OFWSTKSZ 4096 /* 4K Open Firmware stack */ /* @@ -119,6 +121,10 @@ ASENTRY_NOPROF(ofwcall) addis %r5,%r2,TOC_REF(ofmsr)@ha ld %r5,TOC_REF(ofmsr)@l(%r5) ld %r5,0(%r5) +#if defined(__LITTLE_ENDIAN__) && defined(QEMU) + /* QEMU hack: qemu does not emulate mtmsrd correctly! */ + ori %r5,%r5,1 /* Leave PSR_LE set */ +#endif mtmsrd %r5 isync @@ -270,6 +276,10 @@ ASENTRY_NOPROF(rtascall) addis %r7,%r2,TOC_REF(rtasmsr)@ha ld %r7,TOC_REF(rtasmsr)@l(%r7) ld %r7,0(%r7) +#ifdef __LITTLE_ENDIAN__ + /* QEMU hack: qemu does not emulate mtmsrd correctly! */ + ori %r7,%r7,1 /* Leave PSR_LE set */ +#endif mtmsrd %r7 isync diff --git a/sys/powerpc/powernv/opalcall.S b/sys/powerpc/powernv/opalcall.S index 1d1f60353ad..56ba5c7f186 100644 --- a/sys/powerpc/powernv/opalcall.S +++ b/sys/powerpc/powernv/opalcall.S @@ -27,6 +27,8 @@ #include +#include "opt_platform.h" + GLOBAL(opal_entrypoint) .llong 0 GLOBAL(opal_data) @@ -70,8 +72,17 @@ ASENTRY(opal_call) ld %r2,TOC_REF(opal_data)@l(%r2) ld %r2,0(%r2) + +#if defined(__LITTLE_ENDIAN__) && defined(QEMU) + /* QEMU hack: qemu does not emulate mtmsrd correctly! */ + ori %r3,%r3,1 /* Leave PSR_LE set */ +#endif mtmsrd %r3 isync +#if defined(__LITTLE_ENDIAN__) && defined(QEMU) + /* Clean up from qemu hack */ + xori %r3,%r3,1 +#endif /* Shift registers over */ mr %r3,%r4