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Message-ID: <CAAhR5DH9UJ+fFbePPbKsdUiyk63dhE6-f-uazu-s60dPe_Rfrg@mail.gmail.com>
Date: Tue, 23 Jul 2024 14:55:37 -0500
From: Sagi Shahar <sagis@...gle.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: linux-kselftest@...r.kernel.org, Ackerley Tng <ackerleytng@...gle.com>,
Erdem Aktas <erdemaktas@...gle.com>, Isaku Yamahata <isaku.yamahata@...el.com>,
Ryan Afranji <afranji@...gle.com>, Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, Peter Gonda <pgonda@...gle.com>,
Haibo Xu <haibo1.xu@...el.com>, Chao Peng <chao.p.peng@...ux.intel.com>,
Vishal Annapurve <vannapurve@...gle.com>, Roger Wang <runanwang@...gle.com>,
Vipin Sharma <vipinsh@...gle.com>, jmattson@...gle.com, dmatlack@...gle.com,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH v5 01/29] KVM: selftests: Add function to allow
one-to-one GVA to GPA mappings
On Tue, Feb 20, 2024 at 7:43 PM Binbin Wu <binbin.wu@...ux.intel.com> wrote:
>
>
>
> On 12/13/2023 4:46 AM, Sagi Shahar wrote:
> > From: Ackerley Tng <ackerleytng@...gle.com>
> >
> > One-to-one GVA to GPA mappings can be used in the guest to set up boot
> > sequences during which paging is enabled, hence requiring a transition
> > from using physical to virtual addresses in consecutive instructions.
> >
> > Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
> > Signed-off-by: Ryan Afranji <afranji@...gle.com>
> > Signed-off-by: Sagi Shahar <sagis@...gle.com>
> > ---
> > .../selftests/kvm/include/kvm_util_base.h | 2 +
> > tools/testing/selftests/kvm/lib/kvm_util.c | 63 ++++++++++++++++---
> > 2 files changed, 55 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
> > index 1426e88ebdc7..c2e5c5f25dfc 100644
> > --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> > +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> > @@ -564,6 +564,8 @@ vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min);
> > vm_vaddr_t __vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min,
> > enum kvm_mem_region_type type);
> > vm_vaddr_t vm_vaddr_alloc_shared(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min);
> > +vm_vaddr_t vm_vaddr_alloc_1to1(struct kvm_vm *vm, size_t sz,
> > + vm_vaddr_t vaddr_min, uint32_t data_memslot);
> > vm_vaddr_t vm_vaddr_alloc_pages(struct kvm_vm *vm, int nr_pages);
> > vm_vaddr_t __vm_vaddr_alloc_page(struct kvm_vm *vm,
> > enum kvm_mem_region_type type);
> > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> > index febc63d7a46b..4f1ae0f1eef0 100644
> > --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> > @@ -1388,17 +1388,37 @@ vm_vaddr_t vm_vaddr_unused_gap(struct kvm_vm *vm, size_t sz,
> > return pgidx_start * vm->page_size;
> > }
> >
> > +/*
> > + * VM Virtual Address Allocate Shared/Encrypted
> > + *
> > + * Input Args:
> > + * vm - Virtual Machine
> > + * sz - Size in bytes
> > + * vaddr_min - Minimum starting virtual address
> > + * paddr_min - Minimum starting physical address
> > + * data_memslot - memslot number to allocate in
> > + * encrypt - Whether the region should be handled as encrypted
> > + *
> > + * Output Args: None
> > + *
> > + * Return:
> > + * Starting guest virtual address
> > + *
> > + * Allocates at least sz bytes within the virtual address space of the vm
> > + * given by vm. The allocated bytes are mapped to a virtual address >=
> > + * the address given by vaddr_min. Note that each allocation uses a
> > + * a unique set of pages, with the minimum real allocation being at least
> > + * a page.
> > + */
> > static vm_vaddr_t ____vm_vaddr_alloc(struct kvm_vm *vm, size_t sz,
> > - vm_vaddr_t vaddr_min,
> > - enum kvm_mem_region_type type,
> > - bool encrypt)
> > + vm_vaddr_t vaddr_min, vm_paddr_t paddr_min,
> > + uint32_t data_memslot, bool encrypt)
> > {
> > uint64_t pages = (sz >> vm->page_shift) + ((sz % vm->page_size) != 0);
> >
> > virt_pgd_alloc(vm);
> > - vm_paddr_t paddr = _vm_phy_pages_alloc(vm, pages,
> > - KVM_UTIL_MIN_PFN * vm->page_size,
> > - vm->memslots[type], encrypt);
> > + vm_paddr_t paddr = _vm_phy_pages_alloc(vm, pages, paddr_min,
> > + data_memslot, encrypt);
> >
> > /*
> > * Find an unused range of virtual page addresses of at least
> > @@ -1408,8 +1428,7 @@ static vm_vaddr_t ____vm_vaddr_alloc(struct kvm_vm *vm, size_t sz,
> >
> > /* Map the virtual pages. */
> > for (vm_vaddr_t vaddr = vaddr_start; pages > 0;
> > - pages--, vaddr += vm->page_size, paddr += vm->page_size) {
> > -
> > + pages--, vaddr += vm->page_size, paddr += vm->page_size) {
> > virt_pg_map(vm, vaddr, paddr);
> >
> > sparsebit_set(vm->vpages_mapped, vaddr >> vm->page_shift);
> > @@ -1421,12 +1440,16 @@ static vm_vaddr_t ____vm_vaddr_alloc(struct kvm_vm *vm, size_t sz,
> > vm_vaddr_t __vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min,
> > enum kvm_mem_region_type type)
> > {
> > - return ____vm_vaddr_alloc(vm, sz, vaddr_min, type, vm->protected);
> > + return ____vm_vaddr_alloc(vm, sz, vaddr_min,
> > + KVM_UTIL_MIN_PFN * vm->page_size,
> > + vm->memslots[type], vm->protected);
> > }
> >
> > vm_vaddr_t vm_vaddr_alloc_shared(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min)
> > {
> > - return ____vm_vaddr_alloc(vm, sz, vaddr_min, MEM_REGION_TEST_DATA, false);
> > + return ____vm_vaddr_alloc(vm, sz, vaddr_min,
> > + KVM_UTIL_MIN_PFN * vm->page_size,
> > + vm->memslots[MEM_REGION_TEST_DATA], false);
> > }
> >
> > /*
> > @@ -1453,6 +1476,26 @@ vm_vaddr_t vm_vaddr_alloc(struct kvm_vm *vm, size_t sz, vm_vaddr_t vaddr_min)
> > return __vm_vaddr_alloc(vm, sz, vaddr_min, MEM_REGION_TEST_DATA);
> > }
> >
> > +/**
> > + * Allocate memory in @vm of size @sz in memslot with id @data_memslot,
> > + * beginning with the desired address of @vaddr_min.
> > + *
> > + * If there isn't enough memory at @vaddr_min, find the next possible address
> > + * that can meet the requested size in the given memslot.
> > + *
> > + * Return the address where the memory is allocated.
> > + */
> > +vm_vaddr_t vm_vaddr_alloc_1to1(struct kvm_vm *vm, size_t sz,
> > + vm_vaddr_t vaddr_min, uint32_t data_memslot)
> > +{
> > + vm_vaddr_t gva = ____vm_vaddr_alloc(vm, sz, vaddr_min,
> > + (vm_paddr_t)vaddr_min, data_memslot,
> > + vm->protected);
> > + TEST_ASSERT_EQ(gva, addr_gva2gpa(vm, gva));
>
> How can this be guaranteed?
> For ____vm_vaddr_alloc(), generically there is no enforcement about the
> identity of virtual and physical address.
The problem is that if the allocation won't be 1-to-1 the tests won't
work. So we figured it's better to fail early.
The way this is used in practice generally guarantees that the mapping
can be 1-to-1 since we create these mappings at an early stage.
>
> > +
> > + return gva;
> > +}
> > +
> > /*
> > * VM Virtual Address Allocate Pages
> > *
>
>
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