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SubjectRe: [RFC PATCH 5/6] kvm: x86: add KVM_EXIT_MEMORY_ERROR exit
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On 11.11.2021 16.13, Chao Peng wrote:
> Currently support to exit to userspace for private/shared memory
> conversion.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> ---
> arch/x86/kvm/mmu/mmu.c | 20 ++++++++++++++++++++
> include/uapi/linux/kvm.h | 15 +++++++++++++++
> 2 files changed, 35 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index af5ecf4ef62a..780868888aa8 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3950,6 +3950,17 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
>
> slot = __kvm_vcpu_gfn_to_memslot(vcpu, gfn, private);
>
> + /*
> + * Exit to userspace to map the requested private/shared memory region
> + * if there is no memslot and (a) the access is private or (b) there is
> + * an existing private memslot. Emulated MMIO must be accessed through
> + * shared GPAs, thus a memslot miss on a private GPA is always handled
> + * as an implicit conversion "request".
> + */
> + if (!slot &&
> + (private || __kvm_vcpu_gfn_to_memslot(vcpu, gfn, true)))
> + goto out_convert;
> +
> /* Don't expose aliases for no slot GFNs or private memslots */
> if ((cr2_or_gpa & vcpu_gpa_stolen_mask(vcpu)) &&
> !kvm_is_visible_memslot(slot)) {
> @@ -3994,6 +4005,15 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
> *pfn = __gfn_to_pfn_memslot(slot, gfn, false, NULL,
> write, writable, hva);
> return false;
> +
> +out_convert:
> + vcpu->run->exit_reason = KVM_EXIT_MEMORY_ERROR;
> + vcpu->run->mem.type = private ? KVM_EXIT_MEM_MAP_PRIVATE
> + : KVM_EXIT_MEM_MAP_SHARE;
> + vcpu->run->mem.u.map.gpa = cr2_or_gpa;
> + vcpu->run->mem.u.map.size = PAGE_SIZE;
> + return true;
> +
>
I think this does just retry, no exit to user space?




> }
>
> static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8d20caae9180..470c472a9451 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -233,6 +233,18 @@ struct kvm_xen_exit {
> } u;
> };
>
> +struct kvm_memory_exit {
> +#define KVM_EXIT_MEM_MAP_SHARE 1
> +#define KVM_EXIT_MEM_MAP_PRIVATE 2
> + __u32 type;
> + union {
> + struct {
> + __u64 gpa;
> + __u64 size;
> + } map;
> + } u;
> +};
> +
> #define KVM_S390_GET_SKEYS_NONE 1
> #define KVM_S390_SKEYS_MAX 1048576
>
> @@ -272,6 +284,7 @@ struct kvm_xen_exit {
> #define KVM_EXIT_X86_BUS_LOCK 33
> #define KVM_EXIT_XEN 34
> #define KVM_EXIT_TDVMCALL 35
> +#define KVM_EXIT_MEMORY_ERROR 36
>
> /* For KVM_EXIT_INTERNAL_ERROR */
> /* Emulate instruction failed. */
> @@ -455,6 +468,8 @@ struct kvm_run {
> __u64 subfunc;
> __u64 param[4];
> } tdvmcall;
> + /* KVM_EXIT_MEMORY_ERROR */
> + struct kvm_memory_exit mem;
> /* Fix the size of the union. */
> char padding[256];
> };

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