When instrumenting memory accesses for plugin, we force memory accesses
to use the slow path for mmu [1]. This create a situation where we end
up calling ptw_setl_slow. This was fixed recently in [2] but the issue
still could appear out of plugins use case.
Since this function gets called during a cpu_exec, start_exclusive then
hangs. This exclusive section was introduced initially for security
reasons [3].
I suspect this code path was never triggered, because ptw_setl_slow
would always be called transitively from cpu_exec, resulting in a hang.
[1] 6d03226b42
[2] 115ade42d5
[3] https://gitlab.com/qemu-project/qemu/-/issues/279
Fixes: https://gitlab.com/qemu-project/qemu/-/issues/2566
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20241025175857.2554252-2-pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Pointers to the x86 CPU state already exist at the function scope,
no need to re-obtain them in individual exit reason cases.
Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
Link: https://lore.kernel.org/r/20241105155800.5461-6-phil@philjordan.eu
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When setting the APICBASE MSR to an illegal value, the APIC
implementation will return an error. This change forwards that report
to the guest as an exception rather than ignoring it when using the hvf
accelerator.
Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
Link: https://lore.kernel.org/r/20241105155800.5461-5-phil@philjordan.eu
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The hvf_caps data structure only exists once as part of the hvf accelerator
state, but it is initialised during vCPU initialisation. This change therefore
adds a check to ensure memory for it is only allocated once.
Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
Link: https://lore.kernel.org/r/20241105155800.5461-4-phil@philjordan.eu
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The handling for CPUID function 0xD (supported XSAVE features) was
improved in a recent patch. Unfortunately, this appears to have
introduced undefined behaviour for cases where ecx > 30, as the result
of (1 << idx) is undefined if idx > 30.
Per Intel SDM section 13.2, the behaviour for ecx values up to and
including 62 are specified. This change therefore specifically sets
all registers returned by the CPUID instruction to 0 for 63 and higher.
Furthermore, the bit shift uses uint64_t, where behaviour for the entire
range of 2..62 is safe and correct.
Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
Link: https://lore.kernel.org/r/20241105155800.5461-3-phil@philjordan.eu
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Support for x2APIC mode was recently introduced in the software emulated
APIC implementation for TCG. Enabling it when using macOS’s hvf
accelerator is useful and significantly helps performance, as Qemu
currently uses the emulated APIC when running on hvf as well.
This change wires up the read & write operations for the MSR VM exits
and allow-lists the CPUID flag in the x86 hvf runtime.
Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
Link: https://lore.kernel.org/r/20241105155800.5461-2-phil@philjordan.eu
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Commit b56617bbcb ("target/i386: Walk NPT in guest real mode") added
logic to run the page table walker even in real mode if we are in NPT
mode. That function then determined whether real mode or paging is
active based on whether the pg_mode variable was 0.
Unfortunately pg_mode is 0 in two situations:
1) Paging is disabled (real mode)
2) Paging is in 2-level paging mode (32bit without PAE)
That means the walker now assumed that 2-level paging mode was real
mode, breaking NetBSD as well as Windows XP.
To fix that, this patch adds a new PG flag to pg_mode which indicates
whether paging is active at all and uses that to determine whether we
are in real mode or not.
Cc: qemu-stable@nongnu.org
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2654
Fixes: b56617bbcb ("target/i386: Walk NPT in guest real mode")
Signed-off-by: Alexander Graf <graf@amazon.com>
Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Link: https://lore.kernel.org/r/20241106154329.67218-1-graf@amazon.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
SHA512, SM3, SM4 (CPUID[EAX=7,ECX=1).EAX bits 0 to 2) is supported by
Clearwater Forest processor, add it to QEMU as it does not need any
specific enablement.
See https://lore.kernel.org/kvm/20241105054825.870939-1-tao1.su@linux.intel.com/
for reference.
Reviewed-by: Tao Su <tao1.su@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cache topology needs to be defined based on CPU topology levels. Thus,
define CPU topology enumeration in qapi/machine.json to make it generic
for all architectures.
To match the general topology naming style, rename CPU_TOPO_LEVEL_* to
CPU_TOPOLOGY_LEVEL_*, and rename SMT and package levels to thread and
socket.
Also, enumerate additional topology levels for non-i386 arches, and add
a CPU_TOPOLOGY_LEVEL_DEFAULT to help future smp-cache object to work
with compatibility requirement of arch-specific cache topology models.
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Tested-by: Yongwei Ma <yongwei.ma@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20241101083331.340178-3-zhao1.liu@intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
In the follow-up change, the CPU topology enumeration will be moved to
QAPI. And considerring "invalid" should not be exposed to QAPI as an
unsettable item, so, as a preparation for future changes, remove
"invalid" level from the current CPU topology enumeration structure
and define it by a macro instead.
Due to the removal of the enumeration of "invalid", bit 0 of
CPUX86State.avail_cpu_topo bitmap will no longer correspond to "invalid"
level, but will start at the SMT level. Therefore, to honor this change,
update the encoding rule for CPUID[0x1F].
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-ID: <20241101083331.340178-2-zhao1.liu@intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Set the NaN propagation rule explicitly for the float_status words
used in the x86 target.
This is a no-behaviour-change commit, so we retain the existing
behaviour of using the x87-style "prefer QNaN over SNaN, then prefer
the NaN with the larger significand" for MMX and SSE. This is
however not the documented hardware behaviour, so we leave a TODO
note about what we should be doing instead.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20241025141254.2141506-16-peter.maydell@linaro.org
AVX10 state enumeration in CPUID leaf D and enabling in XCR0 register
are identical to AVX512 state regardless of the supported vector lengths.
Given that some E-cores will support AVX10 but not support AVX512, add
AVX512 state components to guest when AVX10 is enabled.
Based on a patch by Tao Su <tao1.su@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Tested-by: Xuelian Guo <xuelian.guo@intel.com>
Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Link: https://lore.kernel.org/r/20241031085233.425388-8-tao1.su@linux.intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Since the highest supported vector length for a processor implies that
all lesser vector lengths are also supported, add the dependencies of
the supported vector lengths. If all vector lengths aren't supported,
clear AVX10 enable bit as well.
Note that the order of AVX10 related dependencies should be kept as:
CPUID_24_0_EBX_AVX10_128 -> CPUID_24_0_EBX_AVX10_256,
CPUID_24_0_EBX_AVX10_256 -> CPUID_24_0_EBX_AVX10_512,
CPUID_24_0_EBX_AVX10_VL_MASK -> CPUID_7_1_EDX_AVX10,
CPUID_7_1_EDX_AVX10 -> CPUID_24_0_EBX,
so that prevent user from setting weird CPUID combinations, e.g. 256-bits
and 512-bits are supported but 128-bits is not, no vector lengths are
supported but AVX10 enable bit is still set.
Since AVX10_128 will be reserved as 1, adding these dependencies has the
bonus that when user sets -cpu host,-avx10-128, CPUID_7_1_EDX_AVX10 and
CPUID_24_0_EBX will be disabled automatically.
Tested-by: Xuelian Guo <xuelian.guo@intel.com>
Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Link: https://lore.kernel.org/r/20241028024512.156724-5-tao1.su@linux.intel.com
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20241031085233.425388-7-tao1.su@linux.intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
When AVX10 enable bit is set, the 0x24 leaf will be present as "AVX10
Converged Vector ISA leaf" containing fields for the version number and
the supported vector bit lengths.
Introduce avx10-version property so that avx10 version can be controlled
by user and cpu model. Per spec, avx10 version can never be 0, the default
value of avx10-version is set to 0 to determine whether it is specified by
user. The default can come from the device model or, for the max model,
from KVM's reported value.
Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Link: https://lore.kernel.org/r/20241028024512.156724-3-tao1.su@linux.intel.com
Link: https://lore.kernel.org/r/20241028024512.156724-4-tao1.su@linux.intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Xuelian Guo <xuelian.guo@intel.com>
Link: https://lore.kernel.org/r/20241031085233.425388-5-tao1.su@linux.intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Prepare for filtering non-boolean features such as AVX10 version.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Link: https://lore.kernel.org/r/20241031085233.425388-4-tao1.su@linux.intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Right now, QEMU is using the "feature" and "bits" fields of ExtSaveArea
to query the accelerator for the support status of extended save areas.
This is a problem for AVX10, which attaches two feature bits (AVX512F
and AVX10) to the same extended save states.
To keep the AVX10 hacks to the minimum, limit usage of esa->features
and esa->bits. Instead, just query the accelerator for the 0xD leaf.
Do it in common code and clear esa->size if an extended save state is
unsupported.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20241031085233.425388-3-tao1.su@linux.intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This gives greater opportunity for reassociation on x86 targets,
since addition can use the LEA instruction.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If the operands of the arithmetic instruction fit within a half-register,
it's easiest to use a comparison instruction to compute the carry.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This removes the 256 byte parity table from the executable.
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This makes it easier for the compiler to understand which bits are set,
and it also removes "cltq" instructions to canonicalize the output value
as 32-bit signed.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Mostly used for TEST+JG and TEST+JLE, but it is easy to cover
also JBE/JA and JL/JGE; shaves about 0.5% TCG ops.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Most uses of CC_OP_DYNAMIC are for CMP/JB/JE or similar sequences.
We can optimize many of them to avoid computation of the flags.
This eliminates both TCG ops to set up the new cc_op, and helper
instructions because evaluating just ZF is much cheaper.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Assert that op is known and that cc_op_live_ is populated.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Replace arithmetic on cc_op with a helper function.
Assert that the op has a size and that it is valid
for the configuration.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Link: https://lore.kernel.org/r/20240701025115.1265117-6-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Give the first few enumerators explicit integer constants,
align the BWLQ enumerators.
This will be used to simplify ((op - CC_OP_*B) & 3).
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Link: https://lore.kernel.org/r/20240701025115.1265117-4-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Just use CC_OP_EFLAGS; it is not that likely that the flags computed by
CC_OP_CLR survive the end of the basic block, in which case there is no
need to spill cc_op_src.
cc_op_src now does need spilling if the XOR is followed by a memory
operation, but this only costs 0.2% extra TCG ops. They will be recouped
by simplifications in how QEMU evaluates ZF at runtime, which are even
greater with this change.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Make const. Use the read-only strings directly; do not copy
them into an on-stack buffer with snprintf. Allow for holes
in the cc_op_str array, now present with CC_OP_POPCNT.
Fixes: 460231ad36 ("target/i386: give CC_OP_POPCNT low bits corresponding to MO_TL")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Link: https://lore.kernel.org/r/20240701025115.1265117-2-richard.henderson@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Prefer it to gen_ext_tl in the common case where the destination is known.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The call to xgetbv() is passing the ecx value for cpuid function 0xD,
index 0. The xgetbv call thus returns false (OSXSAVE is bit 27, which is
well out of the range of CPUID[0xD,0].ECX) and eax is not modified. While
fixing it, cache the whole computation of supported XCR0 bits since it
will be used for more than just CPUID leaf 0xD.
Furthermore, unsupported subleafs of CPUID 0xD (including all those
corresponding to zero bits in host's XCR0) must be hidden; if OSXSAVE
is not set at all, the whole of CPUID leaf 0xD plus the XSAVE bit must
be hidden.
Finally, unconditionally drop XSTATE_BNDREGS_MASK and XSTATE_BNDCSR_MASK;
real hardware will only show them if the MPX bit is set in CPUID;
this is never the case for hvf_get_supported_cpuid() because QEMU's
Hypervisor.framework support does not handle the VMX fields related to
MPX (even in the unlikely possibility that the host has MPX enabled).
So hide those bits in the new cache_host_xcr0().
Cc: Phil Dennis-Jordan <lists@philjordan.eu>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Newer AMD CPUs support ERAPS (Enhanced Return Address Prediction Security)
feature that enables the auto-clear of RSB entries on a TLB flush, context
switches and VMEXITs. The number of default RSP entries is reflected in
RapSize.
Add the feature bit and feature word to support these features.
CPUID_Fn80000021_EAX
Bits Feature Description
24 ERAPS:
Indicates support for enhanced return address predictor security.
CPUID_Fn80000021_EBX
Bits Feature Description
31-24 Reserved
23:16 RapSize:
Return Address Predictor size. RapSize x 8 is the minimum number
of CALL instructions software needs to execute to flush the RAP.
15-00 MicrocodePatchSize. Read-only.
Reports the size of the Microcode patch in 16-byte multiples.
If 0, the size of the patch is at most 5568 (15C0h) bytes.
Link: https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/programmer-references/57238.zip
Signed-off-by: Babu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/7c62371fe60af1e9bbd853f5f8e949bf2d908bd0.1729807947.git.babu.moger@amd.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
CPUID leaf 0x80000022, i.e. ExtPerfMonAndDbg, advertises new performance
monitoring features for AMD processors. Bit 0 of EAX indicates support
for Performance Monitoring Version 2 (PerfMonV2) features. If found to
be set during PMU initialization, the EBX bits can be used to determine
the number of available counters for different PMUs. It also denotes the
availability of global control and status registers.
Add the required CPUID feature word and feature bit to allow guests to
make use of the PerfMonV2 features.
Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/a96f00ee2637674c63c61e9fc4dee343ea818053.1729807947.git.babu.moger@amd.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The check of cpu->phys_bits to be in range between
[32, TARGET_PHYS_ADDR_SPACE_BITS] in host_cpu_realizefn()
is duplicated with check in x86_cpu_realizefn().
Since the ckeck in x86_cpu_realizefn() is called later and can cover all
the x86 cases. Remove the one in host_cpu_realizefn().
Opportunistically adjust cpu->phys_bits directly in
host_cpu_adjust_phys_bits(), which matches more with the function name.
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20240929085747.2023198-1-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
LFENCE and SFENCE were introduced with the original SSE instruction set;
marking them incorrectly as cpuid(SSE2) causes failures for CPU models
that lack SSE2, for example pentium3.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This argument is no longer used.
Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20241013184733.1423747-4-richard.henderson@linaro.org>
The probe_access_full_mmu function was designed for this purpose,
and does not report the memory operation event to plugins.
Cc: qemu-stable@nongnu.org
Fixes: 6d03226b42 ("plugins: force slow path when plugins instrument memory ops")
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20241013184733.1423747-3-richard.henderson@linaro.org>
When translating virtual to physical address with a guest CPU that
supports nested paging (NPT), we need to perform every page table walk
access indirectly through the NPT, which we correctly do.
However, we treat real mode (no page table walk) special: In that case,
we currently just skip any walks and translate VA -> PA. With NPT
enabled, we also need to then perform NPT walk to do GVA -> GPA -> HPA
which we fail to do so far.
The net result of that is that TCG VMs with NPT enabled that execute
real mode code (like SeaBIOS) end up with GPA==HPA mappings which means
the guest accesses host code and data. This typically shows as failure
to boot guests.
This patch changes the page walk logic for NPT enabled guests so that we
always perform a GVA -> GPA translation and then skip any logic that
requires an actual PTE.
That way, all remaining logic to walk the NPT stays and we successfully
walk the NPT in real mode.
Cc: qemu-stable@nongnu.org
Fixes: fe441054bb ("target-i386: Add NPT support")
Signed-off-by: Alexander Graf <graf@amazon.com>
Reported-by: Eduard Vlad <evlad@amazon.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20240921085712.28902-1-graf@amazon.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
The error message for a "stepping" value that is out of bounds is a
bit odd:
$ qemu-system-x86_64 -cpu qemu64,stepping=16
qemu-system-x86_64: can't apply global qemu64-x86_64-cpu.stepping=16: Property .stepping doesn't take value 16 (minimum: 0, maximum: 15)
The "can't apply global" part is an unfortunate artifact of -cpu's
implementation. Left for another day.
The remainder feels overly verbose. Change it to
qemu64-x86_64-cpu: can't apply global qemu64-x86_64-cpu.stepping=16: parameter 'stepping' can be at most 15
Likewise for "family", "model", and "tsc-frequency".
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20241010150144.986655-6-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Properties "family", "model", and "stepping" are visited as signed
integers. They are backed by bits in CPUX86State member
@cpuid_version. The code to extract and insert these bits mixes
signed and unsigned. Not actually wrong, but avoiding such mixing is
good practice.
Visit them as unsigned integers instead.
This adds a few mildly ugly cast in arguments of error_setg(). The
next commit will get rid of them again.
Property "tsc-frequency" is also visited as signed integer. The value
ultimately flows into the kernel, where it is 31 bits unsigned. The
QEMU code freely mixes int, uint32_t, int64_t. I elect not to attempt
draining this swamp today.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20241010150144.986655-5-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Stack accesses should be explicit and use the privilege level of the
target stack. This ensures that SMAP is not applied when the target
stack is in ring 3.
This fixes a bug wherein i386/tcg assumed that an interrupt return, or a
far call using the CALL or JMP instruction, was always going from kernel
or user mode to kernel mode when using a call gate. This assumption is
violated if the call gate has a DPL that is greater than 0.
Analyzed-by: Robert R. Henry <rrh.henry@gmail.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/249
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
