Re: [PATCH v10 0/9] KVM: mm: fd-based approach for supporting KVM

Kirill A. Shutemov
2023-01-16T13:58:23Z

On Sat, Jan 14, 2023 at 12:37:59AM +0000, Sean Christopherson wrote:
> On Fri, Dec 02, 2022, Chao Peng wrote:
> > This patch series implements KVM guest private memory for confidential
> > computing scenarios like Intel TDX[1]. If a TDX host accesses
> > TDX-protected guest memory, machine check can happen which can further
> > crash the running host system, this is terrible for multi-tenant
> > configurations. The host accesses include those from KVM userspace like
> > QEMU. This series addresses KVM userspace induced crash by introducing
> > new mm and KVM interfaces so KVM userspace can still manage guest memory
> > via a fd-based approach, but it can never access the guest memory
> > content.
> >
> > The patch series touches both core mm and KVM code. I appreciate
> > Andrew/Hugh and Paolo/Sean can review and pick these patches. Any other
> > reviews are always welcome.
> > - 01: mm change, target for mm tree
> > - 02-09: KVM change, target for KVM tree
>
> A version with all of my feedback, plus reworked versions of Vishal's selftest,
> is available here:
>
> git@github.com:sean-jc/linux.git x86/upm_base_support
>
> It compiles and passes the selftest, but it's otherwise barely tested. There are
> a few todos (2 I think?) and many of the commits need changelogs, i.e. it's still
> a WIP.
>
> As for next steps, can you (handwaving all of the TDX folks) take a look at what
> I pushed and see if there's anything horrifically broken, and that it still works
> for TDX?

Minor build fix:

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 6eb5336ccc65..4a9e9fa2552a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7211,8 +7211,8 @@ void kvm_arch_set_memory_attributes(struct kvm *kvm,
int level;
bool mixed;

- lockdep_assert_held_write(kvm->mmu_lock);
- lockdep_assert_held(kvm->slots_lock);
+ lockdep_assert_held_write(&kvm->mmu_lock);
+ lockdep_assert_held(&kvm->slots_lock);

/*
* KVM x86 currently only supports KVM_MEMORY_ATTRIBUTE_PRIVATE, skip
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 467916943c73..4ef60ba7eb1d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2304,7 +2304,7 @@ static inline void kvm_account_pgtable_pages(void *virt, int nr)
#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn)
{
- lockdep_assert_held(kvm->mmu_lock);
+ lockdep_assert_held(&kvm->mmu_lock);

return xa_to_value(xa_load(&kvm->mem_attr_array, gfn));
}
--
Kiryl Shutsemau / Kirill A. Shutemov