Re: [PATCH v1 2/4] selftests: kvm: Add processor tests for LoongArch KVM

zhaotianrui
2023-08-03T06:32:19Z

在 2023/8/3 上午2:07, Sean Christopherson 写道:
> On Tue, Aug 01, 2023, Tianrui Zhao wrote:
>> Add processor tests for LoongArch KVM, including vcpu initialize
> Nit, AFAICT these aren't tests, this is simply the core KVM selftests support
> for LoongArch.
Thanks, I will fix this comment.
>
>> and tlb refill exception handler.
>>
>> Based-on: <20230720062813.4126751-1-zhaotianrui@loongson.cn>
>> Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
>> ---
>> .../selftests/kvm/lib/loongarch/exception.S | 27 ++
>> .../selftests/kvm/lib/loongarch/processor.c | 367 ++++++++++++++++++
>> 2 files changed, 394 insertions(+)
>> create mode 100644 tools/testing/selftests/kvm/lib/loongarch/exception.S
>> create mode 100644 tools/testing/selftests/kvm/lib/loongarch/processor.c
>>
>> diff --git a/tools/testing/selftests/kvm/lib/loongarch/exception.S b/tools/testing/selftests/kvm/lib/loongarch/exception.S
>> new file mode 100644
>> index 000000000000..19dc50993da4
>> --- /dev/null
>> +++ b/tools/testing/selftests/kvm/lib/loongarch/exception.S
>> @@ -0,0 +1,27 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +
>> +#include "sysreg.h"
>> +
>> +/* address of refill exception should be 4K aligned */
>> +.align 12
> .align works on bytes, not on shifts. I.e. this will make handle_tlb_refill
> 12-byte aligned, not 4096-byte aligned.
Thanks, I will fix it to .balign 4096.
>
>> +.global handle_tlb_refill
>> +handle_tlb_refill:
>> + csrwr t0, LOONGARCH_CSR_TLBRSAVE
>> + csrrd t0, LOONGARCH_CSR_PGD
>> + lddir t0, t0, 3
>> + lddir t0, t0, 1
>> + ldpte t0, 0
>> + ldpte t0, 1
>> + tlbfill
>> + csrrd t0, LOONGARCH_CSR_TLBRSAVE
>> + ertn
>> +
>> +/* address of general exception should be 4K aligned */
>> +.align 12
> Same thing here.
I will fix it too.
>
>> +.global handle_exception
>> +handle_exception:
>> +1:
>> + nop
>> + b 1b
>> + nop
>> + ertn
>> diff --git a/tools/testing/selftests/kvm/lib/loongarch/processor.c b/tools/testing/selftests/kvm/lib/loongarch/processor.c
>> new file mode 100644
>> index 000000000000..2e50b6e2c556
>> --- /dev/null
>> +++ b/tools/testing/selftests/kvm/lib/loongarch/processor.c
>> @@ -0,0 +1,367 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * KVM selftest LoongArch library code, including CPU-related functions.
>> + *
> Again, unnecessary IMO. If you do keep the comment, the extra line with a bare
> asterisk should be dropped.
Thanks, I will remove this comment.
>
>> + */
>> +
>> +#include <assert.h>
>> +#include <linux/bitfield.h>
>> +#include <linux/compiler.h>
>> +
>> +#include "kvm_util.h"
>> +#include "processor.h"
>> +#include "sysreg.h"
>> +
>> +#define DEFAULT_LOONGARCH_GUEST_STACK_VADDR_MIN 0xac0000
> Why diverge from the common?
>
> #define DEFAULT_GUEST_STACK_VADDR_MIN 0xab6000
>
> AFAIK, the common value is also mostly arbitrary, but that just makes it even
> more confusing as to why LoongArch needs to bump the min by 0x4000.
This is reference from ARM, and I will fix it to use the the common value.
>
>> +uint64_t *virt_get_pte_hva(struct kvm_vm *vm, vm_vaddr_t gva)
>> +{
>> + uint64_t *ptep;
>> +
>> + if (!vm->pgd_created)
>> + goto unmapped_gva;
>> +
>> + ptep = addr_gpa2hva(vm, vm->pgd) + pgd_index(vm, gva) * 8;
>> + if (!ptep)
>> + goto unmapped_gva;
>> +
>> + switch (vm->pgtable_levels) {
>> + case 4:
>> + ptep = addr_gpa2hva(vm, pte_addr(vm, *ptep)) + pud_index(vm, gva) * 8;
>> + if (!ptep)
>> + goto unmapped_gva;
> This wants a "fallthrough" annotation.
Thanks, I will add the "fallthrough" annotation.
>
>> + case 3:
>> + ptep = addr_gpa2hva(vm, pte_addr(vm, *ptep)) + pmd_index(vm, gva) * 8;
>> + if (!ptep)
>> + goto unmapped_gva;
>> + case 2:
>> + ptep = addr_gpa2hva(vm, pte_addr(vm, *ptep)) + pte_index(vm, gva) * 8;
>> + if (!ptep)
>> + goto unmapped_gva;
>> + break;
>> + default:
>> + TEST_FAIL("Page table levels must be 2, 3, or 4");
> Obviously it shouldn't come up, but print the actual pgtable_levels to make debug
> a wee bit easier e.g.
> TEST_FAIL("Got %u page table levels, expected 2, 3, or 4",
> vm->pgtable_levels);
Thanks, I will also print the actual pgtable_levels in this debug function.
>
> Mostly out of curiosity, but also because it looks like this was heavily copy+pasted
> from ARM: does LoongArch actually support 2-level page tables?
Yes, this codes are mostly copy pasted from ARM, but LoongArch does not
support 2-levels page tables, it only support 3-level and 4-level page
tables, and I will fix it.
>> +static void loongarch_set_csr(struct kvm_vcpu *vcpu, uint64_t id, uint64_t val)
>> +{
>> + uint64_t csrid;
>> +
>> + csrid = KVM_REG_LOONGARCH_CSR | KVM_REG_SIZE_U64 | 8 * id;
>> + vcpu_set_reg(vcpu, csrid, val);
>> +}
>> +
>> +static void loongarch_vcpu_setup(struct kvm_vcpu *vcpu)
>> +{
>> + unsigned long val;
>> + int width;
>> + struct kvm_vm *vm = vcpu->vm;
>> +
>> + switch (vm->mode) {
>> + case VM_MODE_P48V48_16K:
>> + case VM_MODE_P40V48_16K:
>> + case VM_MODE_P36V48_16K:
>> + case VM_MODE_P36V47_16K:
>> + break;
>> +
>> + default:
>> + TEST_FAIL("Unknown guest mode, mode: 0x%x", vm->mode);
>> + }
>> +
>> + /* user mode and page enable mode */
>> + val = PLV_USER | CSR_CRMD_PG;
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_CRMD, val);
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_PRMD, val);
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_EUEN, 1);
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_ECFG, 0);
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_TCFG, 0);
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_ASID, 1);
>> +
>> + width = vm->page_shift - 3;
>> + val = 0;
>> + switch (vm->pgtable_levels) {
>> + case 4:
>> + /* pud page shift and width */
>> + val = (vm->page_shift + width * 2) << 20 | (width << 25);
>> + case 3:
>> + /* pmd page shift and width */
>> + val |= (vm->page_shift + width) << 10 | (width << 15);
>> + case 2:
>> + /* pte page shift and width */
>> + val |= vm->page_shift | width << 5;
>> + break;
>> + default:
>> + TEST_FAIL("Page table levels must be 2, 3, or 4");
>> + }
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_PWCTL0, val);
>> +
>> + /* pgd page shift and width */
>> + val = (vm->page_shift + width * (vm->pgtable_levels - 1)) | width << 6;
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_PWCTL1, val);
>> +
>> + loongarch_set_csr(vcpu, LOONGARCH_CSR_PGDL, vm->pgd);
>> +
>> + extern void handle_tlb_refill(void);
>> + extern void handle_exception(void);
> Eww. I get that it's probably undesirable to expose these via processor.h, but
> at least declare them outside of the function.
Thanks, I will declare them outside of the function.
>
>> +struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
>> + void *guest_code)
>> +{
>> + return loongarch_vcpu_add(vm, vcpu_id, guest_code);
> Please drop the single-line passthrough, i.e. drop loongarch_vcpu_add(). I'm
> guessing you copy+pasted much of this from ARM. ARM's passthrough isn't a pure
> passthrough, which is directly related to why the "passthrough" is ok: there are
> other callers to aarch64_vcpu_add() that pass a non-NULL @source.
Yes, this is also copy pasted from ARM, and I will drop the
loongarch_vcpu_add() function and move the content of it to here.