Re: [PATCH 2/4] KVM: x86: Replace kvm_read_{cr0,cr4}_bits() with kvm_is_{cr0,cr4}_bit_set()

[Sean Christopherson <seanjc@google.com>]

On Wed, Mar 22, 2023, Binbin Wu wrote:
> Replace kvm_read_{cr0,cr4}_bits() with kvm_is_{cr0,cr4}_bit_set() when only
> one bit is checked and bool is preferred as return value type.
> Also change the return value type from int to bool of is_pae(), is_pse() and
> is_paging().

I'm going to squash the obvious/direct changes with the introduction of the helpers,
and isolate is_{pae,pse,paging}() as those are more risky due to the multiple
casts (ulong=>int=>bool), and because the end usage isn't visible in the patch.

Case in point, there is a benign but in svm_set_cr0() that would be silently
fixed by converting is_paging() to return a bool:

	bool old_paging = is_paging(vcpu);

	...

	vcpu->arch.cr0 = cr0;

	if (!npt_enabled) {
		hcr0 |= X86_CR0_PG | X86_CR0_WP;
		if (old_paging != is_paging(vcpu))

The "old_paging != is_paging(vcpu)" compares a bool (1/0) against an int that
was an unsigned long (X86_CR0_PG/0), i.e. gets a false positive when paging is
enabled.

I'll post a fix and slot it in before this patch, both so that there's no silent
fixes and so that this changelog can reference the commit.

> ---
>  arch/x86/kvm/cpuid.c      |  4 ++--
>  arch/x86/kvm/mmu.h        |  2 +-
>  arch/x86/kvm/vmx/nested.c |  2 +-
>  arch/x86/kvm/vmx/vmx.c    |  2 +-
>  arch/x86/kvm/x86.c        | 20 ++++++++++----------
>  arch/x86/kvm/x86.h        | 16 ++++++++--------

This misses a few conversions in kvm_pmu_rdpmc(), I'll fix those when applying too.