On 13/05/2015 13:31, Andrew Jones wrote:
> Commit 1050dcda30529 introduced KVM_MEMSLOT_INCOHERENT to flag memory
> regions that may have coherency issues due to mapping host system RAM
> as non-cacheable. This was introduced as a KVM internal flag, but now
> give KVM userspace access to it so that it may use it for hinting
> likely problematic regions. Also rename to KVM_MEM_UNCACHED.
>
> Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> ---
> Documentation/virtual/kvm/api.txt | 20 ++++++++++++++------
> arch/arm/include/uapi/asm/kvm.h | 1 +
> arch/arm/kvm/arm.c | 1 +
> arch/arm/kvm/mmu.c | 4 ++--
> arch/arm64/include/uapi/asm/kvm.h | 1 +
> include/linux/kvm_host.h | 1 -
> include/uapi/linux/kvm.h | 2 ++
> virt/kvm/kvm_main.c | 7 ++++++-
> 8 files changed, 27 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 9fa2bf8c3f6f1..04ffd9f5db5f2 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -905,6 +905,7 @@ struct kvm_userspace_memory_region {
> /* for kvm_memory_region::flags */
> #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
> #define KVM_MEM_READONLY (1UL << 1)
> +#define KVM_MEM_UNCACHED (1UL << 2)
>
> This ioctl allows the user to create or modify a guest physical memory
> slot. When changing an existing slot, it may be moved in the guest
> @@ -920,12 +921,19 @@ It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
> be identical. This allows large pages in the guest to be backed by large
> pages in the host.
>
> -The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and
> -KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of
> -writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to
> -use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it,
> -to make a new slot read-only. In this case, writes to this memory will be
> -posted to userspace as KVM_EXIT_MMIO exits.
> +The flags field supports the following flags. All flags may be used in
> +combination.
> + - KVM_MEM_LOG_DIRTY_PAGES: no capability required
> + Set this to instruct KVM to keep track of writes to memory within
> + the slot. (See the KVM_GET_DIRTY_LOG ioctl)
> + - KVM_MEM_READONLY: depends on capability KVM_CAP_READONLY_MEM
> + Set this to make a new slot read-only. In this case, writes to
> + this memory will be posted to userspace as KVM_EXIT_MMIO exits.
> + EINVAL will be returned if the slot is not new.
> + - KVM_MEM_UNCACHED: depends on capability KVM_CAP_UNCACHED_MEM
> + Set this to make a new slot uncached, i.e. userspace will always
> + directly read/write RAM for this memory region. EINVAL will be
> + returned if the slot is not new.
>
> When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of
> the memory region are automatically reflected into the guest. For example, an
> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
> index df3f60cb1168a..893a331655115 100644
> --- a/arch/arm/include/uapi/asm/kvm.h
> +++ b/arch/arm/include/uapi/asm/kvm.h
> @@ -26,6 +26,7 @@
> #define __KVM_HAVE_GUEST_DEBUG
> #define __KVM_HAVE_IRQ_LINE
> #define __KVM_HAVE_READONLY_MEM
> +#define __KVM_HAVE_UNCACHED_MEM
>
> #define KVM_REG_SIZE(id) \
> (1U << (((id) & KVM_REG_SIZE_MASK) >> KVM_REG_SIZE_SHIFT))
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index d9631ecddd56e..cbb532de9c8b5 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -182,6 +182,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_ARM_PSCI_0_2:
> case KVM_CAP_READONLY_MEM:
> case KVM_CAP_MP_STATE:
> + case KVM_CAP_UNCACHED_MEM:
> r = 1;
> break;
> case KVM_CAP_COALESCED_MMIO:
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 1d5accbd3dcf2..bc1665acd73e7 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -1307,7 +1307,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> if (!hugetlb && !force_pte)
> hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa);
>
> - fault_ipa_uncached = memslot->flags & KVM_MEMSLOT_INCOHERENT;
> + fault_ipa_uncached = memslot->flags & KVM_MEM_UNCACHED;
>
> if (hugetlb) {
> pmd_t new_pmd = pfn_pmd(pfn, mem_type);
> @@ -1834,7 +1834,7 @@ int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot,
> * regions as incoherent.
> */
> if (slot->flags & KVM_MEM_READONLY)
> - slot->flags |= KVM_MEMSLOT_INCOHERENT;
> + slot->flags |= KVM_MEM_UNCACHED;
> return 0;
> }
>
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index d26832022127e..be46855ca01b7 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -38,6 +38,7 @@
> #define __KVM_HAVE_GUEST_DEBUG
> #define __KVM_HAVE_IRQ_LINE
> #define __KVM_HAVE_READONLY_MEM
> +#define __KVM_HAVE_UNCACHED_MEM
>
> #define KVM_REG_SIZE(id) \
> (1U << (((id) & KVM_REG_SIZE_MASK) >> KVM_REG_SIZE_SHIFT))
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index ad45054309a0f..74d6a14529f53 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -39,7 +39,6 @@
> * include/linux/kvm_h.
> */
> #define KVM_MEMSLOT_INVALID (1UL << 16)
> -#define KVM_MEMSLOT_INCOHERENT (1UL << 17)
>
> /* Two fragments for cross MMIO pages. */
> #define KVM_MAX_MMIO_FRAGMENTS 2
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 4b60056776d14..ceb6e805e5f77 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -108,6 +108,7 @@ struct kvm_userspace_memory_region {
> */
> #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
> #define KVM_MEM_READONLY (1UL << 1)
> +#define KVM_MEM_UNCACHED (1UL << 2)
>
> /* for KVM_IRQ_LINE */
> struct kvm_irq_level {
> @@ -814,6 +815,7 @@ struct kvm_ppc_smmu_info {
> #define KVM_CAP_S390_INJECT_IRQ 113
> #define KVM_CAP_S390_IRQ_STATE 114
> #define KVM_CAP_PPC_HWRNG 115
> +#define KVM_CAP_UNCACHED_MEM 116
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 90977418aeb6e..d1d535d80a075 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -719,6 +719,10 @@ static int check_memory_region_flags(struct kvm_userspace_memory_region *mem)
> valid_flags |= KVM_MEM_READONLY;
> #endif
>
> +#ifdef __KVM_HAVE_UNCACHED_MEM
> + valid_flags |= KVM_MEM_UNCACHED;
> +#endif
> +
> if (mem->flags & ~valid_flags)
> return -EINVAL;
>
> @@ -816,7 +820,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
> else { /* Modify an existing slot. */
> if ((mem->userspace_addr != old.userspace_addr) ||
> (npages != old.npages) ||
> - ((new.flags ^ old.flags) & KVM_MEM_READONLY))
> + ((new.flags ^ old.flags) &
> + (KVM_MEM_READONLY | KVM_MEM_UNCACHED)))
> goto out;
>
> if (base_gfn != old.base_gfn)
>
Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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