linux-kernel - Re: [PATCH 13/18] KVM: selftests: Drop superfluous switch() on vm->mode in vcpu_init

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Message-ID: <diqz7chnm6n0.fsf@ctop-sg.c.googlers.com>
Date: Thu, 28 Mar 2024 02:28:51 +0000
From: Ackerley Tng <ackerleytng@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Paolo Bonzini <pbonzini@...hat.com>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>, Anup Patel <anup@...infault.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/18] KVM: selftests: Drop superfluous switch() on
 vm->mode in vcpu_init_sregs()

Sean Christopherson <seanjc@...gle.com> writes:

> Replace the switch statement on vm->mode in x86's vcpu_init_sregs()'s with
> a simple assert that the VM has a 48-bit virtual address space.  A switch
> statement is both overkill and misleading, as the existing code incorrectly
> implies that VMs with LA57 would need different to configuration for the
> LDT, TSS, and flat segments.  In all likelihood, the only difference that
> would be needed for selftests is CR4.LA57 itself.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  .../selftests/kvm/lib/x86_64/processor.c      | 25 ++++++++-----------
>  1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> index 8547833ffa26..561c0aa93608 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> @@ -555,6 +555,8 @@ static void vcpu_init_sregs(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_sregs sregs;
>  
> +	TEST_ASSERT_EQ(vm->mode, VM_MODE_PXXV48_4K);
> +
>  	/* Set mode specific system register values. */
>  	vcpu_sregs_get(vcpu, &sregs);
>  
> @@ -562,22 +564,15 @@ static void vcpu_init_sregs(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
>  
>  	kvm_setup_gdt(vm, &sregs.gdt);
>  
> -	switch (vm->mode) {
> -	case VM_MODE_PXXV48_4K:
> -		sregs.cr0 = X86_CR0_PE | X86_CR0_NE | X86_CR0_PG;
> -		sregs.cr4 |= X86_CR4_PAE | X86_CR4_OSFXSR;
> -		sregs.efer |= (EFER_LME | EFER_LMA | EFER_NX);
> +	sregs.cr0 = X86_CR0_PE | X86_CR0_NE | X86_CR0_PG;
> +	sregs.cr4 |= X86_CR4_PAE | X86_CR4_OSFXSR;
> +	sregs.efer |= (EFER_LME | EFER_LMA | EFER_NX);
>  
> -		kvm_seg_set_unusable(&sregs.ldt);
> -		kvm_seg_set_kernel_code_64bit(vm, DEFAULT_CODE_SELECTOR, &sregs.cs);
> -		kvm_seg_set_kernel_data_64bit(vm, DEFAULT_DATA_SELECTOR, &sregs.ds);
> -		kvm_seg_set_kernel_data_64bit(vm, DEFAULT_DATA_SELECTOR, &sregs.es);
> -		kvm_setup_tss_64bit(vm, &sregs.tr, 0x18);
> -		break;
> -
> -	default:
> -		TEST_FAIL("Unknown guest mode, mode: 0x%x", vm->mode);
> -	}
> +	kvm_seg_set_unusable(&sregs.ldt);
> +	kvm_seg_set_kernel_code_64bit(vm, DEFAULT_CODE_SELECTOR, &sregs.cs);
> +	kvm_seg_set_kernel_data_64bit(vm, DEFAULT_DATA_SELECTOR, &sregs.ds);
> +	kvm_seg_set_kernel_data_64bit(vm, DEFAULT_DATA_SELECTOR, &sregs.es);
> +	kvm_setup_tss_64bit(vm, &sregs.tr, 0x18);
>  
>  	sregs.cr3 = vm->pgd;
>  	vcpu_sregs_set(vcpu, &sregs);
> -- 
> 2.44.0.291.gc1ea87d7ee-goog

Reviewed-by: Ackerley Tng <ackerleytng@...gle.com>