In KVM/arm64, values of ID registers for a guest are mostly same as
its host's values except for bits for feature that KVM doesn't support
and for opt-in features that userspace didn't configure. Userspace
can use KVM_SET_ONE_REG to a set ID register value, but it fails
if userspace attempts to modify the register value.
This patch series adds support to allow userspace to modify a value of
ID registers (as long as KVM can support features that are indicated
in the registers) so userspace can have more control of configuring
and unconfiguring features for guests. We need this because we would
like to expose a uniform set/level of features for a group of guests on
systems with different ARM CPUs. Since some features are not binary
in nature (e.g. AA64DFR0_EL1.BRPs fields indicate number of
breakpoints minus 1), using KVM_ARM_VCPU_INIT to control such features
is inconvenient. This will be supported only for AArch64 EL1 guests at
least for now.
The patch series is for both VHE and non-VHE, except for protected VMs,
which have a different way of configuring ID registers based on its
different requirements [1].
There was a patch series that tried to achieve the same thing [2].
A few snippets of codes in this series were inspired by or came from [2].
The initial value of ID registers for a vCPU will be the host's value
with bits cleared for unsupported features and for opt-in features that
were not configured. So, the initial value userspace can see (via
KVM_GET_ONE_REG) is the upper limit that can be set for the register.
Any requests to change the value that conflicts with opt-in features'
configuration will fail (e.g. if KVM_ARM_VCPU_PMU_V3 is configured by
KVM_ARM_VCPU_INIT, ID_AA64DFR0_EL1.PMUVER cannot be set to zero.
Otherwise, the initial value of ID_AA64DFR0_EL1.PMUVER will be zero,
and cannot be changed from zero).
When a guest tries to use a CPU feature that is not exposed to the guest,
trapping it (to emulate a real CPU's behavior) would generally be a
desirable behavior (when it is possible with no or little side effects).
The later patches in the series add codes for this. Only features that
can be trapped independently will be trapped by this series though.
Highest numbered breakpoints must be context aware breakpoints
(as specified by Arm ARM). If the number of non-context aware
breakpoints for the guest is decreased by userspace (e.g. Lower
ID_AA64DFR0.BRPs keeping ID_AA64DFR0.CTX_CMPs the same), simply
narrowing the breakpoints will be problematic because it will
lead to narrowing context aware breakpoints for the guest. In this
case, KVM will always trap and emulate breakpoints/watchpoints
accesses in that case.
This series adds kunit tests for new functions in sys_regs.c (except for
trivial ones), and these tests are enabled with a new configuration
option 'CONFIG_KVM_KUNIT_TEST'.
The series is based on 5.18-rc3.
Patch 01 introduces arm64_check_features(), which will validate
ID registers based on given arm64_ftr_bits[].
Patch 02 introduces id_regs[] to kvm_arch to save values of ID
registers.
Patches 03-04 introduces structure id_reg_desc to manage the ID register
specific control for the guest.
Patch 05 prohibits modifying values of ID regs for 32bit EL1 guests.
Patches 06-11 introduces id_reg_desc for ID_AA64PFR0_EL1, ID_AA64PFR1_EL1,
ID_AA64ISAR0_EL1, ID_AA64ISAR1_EL1, ID_AA64ISAR2_EL1 and ID_AA64MMFR0_EL1
to make them configurable.
Patches 12-14 take cares emulation of dbgbcr/dbgbvr/dbgwcr when the number
of non-context aware breakpoints are reduced for the guest.
Patches 15-19 introduces id_reg_desc for remaining ID registers to
make them configurable.
Patch 20 switches to use id_reg_desc_table[] for ID registers instead
of sys_reg_descs[].
Patch 21 introduces consistency checking of feature fractional
fields of ID registers at the first KVM_RUN.
Patch 22 introduces a new capability KVM_CAP_ARM_ID_REG_WRITABLE
to identify that ID registers are configurable by userspace.
Patch 23 introduces kunit test cases for sys_reg.c changes.
Patches 24-25 change the way of using vcpu->arch.cptr_el2/mdcr_el2 to
track certain bits of cptr_el2/mdcr_el2 in the vcpu->arch fields and use
them when setting them for the guest. The following patches will update
the vcpu->arch fields based on available features for the guest.
Patch 26 introduces struct feature_config_ctrl and some helper
functions to enable trapping of features that are disabled for a guest.
Patches 27-31 add feature_config_ctrl for CPU features, which are
used to program configuration registers to trap each of the features.
Patch 32 adds kunit test cases for changes in patches 26-31.
Patch 33 adds a couple of helpers for selftests to extract a field of
ID registers.
Patch 34 adds a selftest to validate reading/writing ID registers.
Patches 35-38 add test cases for dbgbcr/dbgbvr/dbgwcr emulation
to the debug-exceptions test.
v7:
- Add emulation of dbgbcr/dbgbvr/dbgwcr when the number of non-context
aware breakpoints are reduced for the guest.
- Add an array of arm64_ftr_bits to id_reg_desc so that KVM could
have its own validation policy of ID registers.
- Don't support configurable ID registers for 32bit EL1 guest.
- Change the ID register validation function in cpufeature.c to
accept arm64_ftr_bits as an argument.
- Don't allocate buffers in kvm_arch for ID registers with CRm==0.
[Oliver]
- Change set_default_id_regs() not to walk the entire sys_reg_descs[]
in the patch-2. [Oliver]
- Add id_reg_desc for ID_AA64ISAR0_EL1
v6: https://lore.kernel.org/all/20220311044811.1980336-1-reijiw@xxxxxxxxxx/
- Remove entries for all ID register entries from sys_reg_descs[],
and use id_reg_desc_table[] for ID registers instead. [Oliver]
- Remove sys_reg field from id_reg_info, add reg_desc (sys_reg_desc)
field to id_reg_info, and rename 'id_reg_info' to 'id_reg_desc'.
- Merge the following three patches of v5 into one patch "KVM: arm64:
Make ID_AA64DFR0_EL1/ID_DFR0_EL1 writable" to accept userspace's
request to set ID_AA64DFR0_EL1.PMUVER/ID_DFR0_EL1.PERFMON to 0xf
(they are set to 0 though) even after applying the patch-10. [Oliver]
patch-10 KVM: arm64: Hide IMPLEMENTATION DEFINED PMU support for the guest
patch-11 KVM: arm64: Make ID_AA64DFR0_EL1 writable"
patch-12 KVM: arm64: Make ID_DFR0_EL1 writable"
v5: https://lore.kernel.org/all/20220214065746.1230608-1-reijiw@xxxxxxxxxx/
- Change the return value of kcalloc failure of init_arm64_ftr_bits_kvm
to -ENOMEM from ENOMEM. [Fuad]
- Call init_arm64_ftr_bits_kvm from init_cpu_features(). [Ricardo, Fuad]
- Move is_id_reg() in arch/arm64/kvm/sys_regs.c. [Fuad]
- Remove frac_ftr_check from feature_frac [Fuad]
- Rename kvm_id_regs_consistency_check() [Fuad]
- Add feature_config_ctrl for ID_AA64DFR0_TRACEVER [Fuad]
- Move changes for kvm_set_id_reg_feature and __modify_kvm_id_reg from
patch-4 to patch-3. [Fuad]
- Comment additions and fixes [Fuad]
- Rename arm64_check_features() [Ricardo]
- Run arm64_check_features_kvm() for the default guest value [Ricardo]
- Add ID_AA64MMFR1_EL1.HAFDBS validation
- Cosmetic fixes
v4: https://lore.kernel.org/all/20220106042708.2869332-1-reijiw@xxxxxxxxxx/
- Make ID registers storage per VM instead of per vCPU. [Marc]
- Implement arm64_check_features() in arch/arm64/kernel/cpufeature.c
by using existing codes in the file. [Marc]
- Use a configuration function to enable traps for disabled
features. [Marc]
- Document ID registers become immutable after the first KVM_RUN [Eric]
- Update ID_AA64PFR0.GIC at the point where a GICv3 is created. [Marc]
- Get TGranX's bit position by substracting 12 from TGranX_2's bit
position. [Eric]
- Don't validate AArch32 ID registers when the system doesn't support
32bit EL0. [Eric]
- Add/fixes comments for patches. [Eric]
- Made bug fixes/improvements of the selftest. [Eric]
- Added .kunitconfig for arm64 KUnit tests
v3: https://lore.kernel.org/all/20211117064359.2362060-1-reijiw@xxxxxxxxxx/
- Remove ID register consistency checking across vCPUs. [Oliver]
- Change KVM_CAP_ARM_ID_REG_WRITABLE to
KVM_CAP_ARM_ID_REG_CONFIGURABLE. [Oliver]
- Add KUnit testing for ID register validation and trap initialization.
- Change read_id_reg() to take care of ID_AA64PFR0_EL1.GIC.
- Add a helper of read_id_reg() (__read_id_reg()) and use the helper
instead of directly using __vcpu_sys_reg().
- Change not to run kvm_id_regs_consistency_check() and
kvm_vcpu_init_traps() for protected VMs.
- Update selftest to remove test cases for ID register consistency.
checking across vCPUs and to add test cases for ID_AA64PFR0_EL1.GIC.
v2: https://lore.kernel.org/all/20211103062520.1445832-1-reijiw@xxxxxxxxxx/
- Remove unnecessary line breaks. [Andrew]
- Use @params for comments. [Andrew]
- Move arm64_check_features to arch/arm64/kvm/sys_regs.c and
change that KVM specific feature check function. [Andrew]
- Remove unnecessary raz handling from __set_id_reg. [Andrew]
- Remove sys_val field from the initial id_reg_info and add it
in the later patch. [Andrew]
- Call id_reg->init() from id_reg_info_init(). [Andrew]
- Fix cpuid_feature_cap_perfmon_field() to convert 0xf to 0x0
(and use it in the following patches).
- Change kvm_vcpu_first_run_init to set has_run_once to false
when kvm_id_regs_consistency_check() fails.
- Add a patch to introduce id_reg_info for ID_AA64MMFR0_EL1,
which requires special validity checking for TGran*_2 fields.
- Add patches to introduce id_reg_info for ID_DFR1_EL1 and
ID_MMFR0_EL1, which are required due to arm64_check_features
implementation change.
- Add a new argument, which is a pointer to id_reg_info, for
id_reg_info's validate().
v1: https://lore.kernel.org/all/20211012043535.500493-1-reijiw@xxxxxxxxxx/
[1] https://lore.kernel.org/all/20211010145636.1950948-1-tabba@xxxxxxxxxx/
[2] https://lore.kernel.org/all/20201102033422.657391-1-liangpeng10@xxxxxxxxxx/
[3] https://lore.kernel.org/all/20220127161759.53553-2-alexandru.elisei@xxxxxxx/
Reiji Watanabe (38):
KVM: arm64: Introduce a validation function for an ID register
KVM: arm64: Save ID registers' sanitized value per guest
KVM: arm64: Introduce struct id_reg_desc
KVM: arm64: Generate id_reg_desc's ftr_bits at KVM init when needed
KVM: arm64: Prohibit modifying values of ID regs for 32bit EL1 guests
KVM: arm64: Make ID_AA64PFR0_EL1 writable
KVM: arm64: Make ID_AA64PFR1_EL1 writable
KVM: arm64: Make ID_AA64ISAR0_EL1 writable
KVM: arm64: Make ID_AA64ISAR1_EL1 writable
KVM: arm64: Make ID_AA64ISAR2_EL1 writable
KVM: arm64: Make ID_AA64MMFR0_EL1 writable
KVM: arm64: Add a KVM flag indicating emulating debug regs access is
needed
KVM: arm64: Emulate dbgbcr/dbgbvr accesses
KVM: arm64: Emulate dbgwcr accesses
KVM: arm64: Make ID_AA64DFR0_EL1/ID_DFR0_EL1 writable
KVM: arm64: KVM: arm64: Make ID_DFR1_EL1 writable
KVM: arm64: KVM: arm64: Make ID_MMFR0_EL1 writable
KVM: arm64: Make MVFR1_EL1 writable
KVM: arm64: Add remaining ID registers to id_reg_desc_table
KVM: arm64: Use id_reg_desc_table for ID registers
KVM: arm64: Add consistency checking for frac fields of ID registers
KVM: arm64: Introduce KVM_CAP_ARM_ID_REG_CONFIGURABLE capability
KVM: arm64: Add kunit test for ID register validation
KVM: arm64: Use vcpu->arch cptr_el2 to track value of cptr_el2 for VHE
KVM: arm64: Use vcpu->arch.mdcr_el2 to track value of mdcr_el2
KVM: arm64: Introduce framework to trap disabled features
KVM: arm64: Trap disabled features of ID_AA64PFR0_EL1
KVM: arm64: Trap disabled features of ID_AA64PFR1_EL1
KVM: arm64: Trap disabled features of ID_AA64DFR0_EL1
KVM: arm64: Trap disabled features of ID_AA64MMFR1_EL1
KVM: arm64: Trap disabled features of ID_AA64ISAR1_EL1
KVM: arm64: Add kunit test for trap initialization
KVM: arm64: selftests: Add helpers to extract a field of ID registers
KVM: arm64: selftests: Introduce id_reg_test
KVM: arm64: selftests: Test linked breakpoint and watchpoint
KVM: arm64: selftests: Test breakpoint/watchpoint register access
KVM: arm64: selftests: Test with every breakpoint/watchpoint
KVM: arm64: selftests: Test breakpoint/watchpoint changing
ID_AA64DFR0_EL1
Documentation/virt/kvm/api.rst | 16 +
arch/arm64/include/asm/cpufeature.h | 3 +-
arch/arm64/include/asm/kvm_arm.h | 32 +
arch/arm64/include/asm/kvm_host.h | 17 +
arch/arm64/include/asm/sysreg.h | 14 +-
arch/arm64/kernel/cpufeature.c | 52 +
arch/arm64/kvm/.kunitconfig | 4 +
arch/arm64/kvm/Kconfig | 11 +
arch/arm64/kvm/arm.c | 24 +-
arch/arm64/kvm/debug.c | 20 +-
arch/arm64/kvm/hyp/vhe/switch.c | 14 +-
arch/arm64/kvm/sys_regs.c | 2363 +++++++++++++++--
arch/arm64/kvm/sys_regs_test.c | 1287 +++++++++
arch/arm64/kvm/vgic/vgic-init.c | 9 +
include/uapi/linux/kvm.h | 1 +
tools/arch/arm64/include/asm/sysreg.h | 1 +
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/aarch64/debug-exceptions.c | 649 ++++-
.../selftests/kvm/aarch64/id_reg_test.c | 1297 +++++++++
.../selftests/kvm/include/aarch64/processor.h | 5 +
.../selftests/kvm/lib/aarch64/processor.c | 27 +
21 files changed, 5549 insertions(+), 298 deletions(-)
create mode 100644 arch/arm64/kvm/.kunitconfig
create mode 100644 arch/arm64/kvm/sys_regs_test.c
create mode 100644 tools/testing/selftests/kvm/aarch64/id_reg_test.c
base-commit: b3fa05b7ec851be680eb51b20ddda0b195b7cdb8
--
2.36.0.rc0.470.gd361397f0d-goog
