Re: [PATCH v3 2/4] KVM: SVM: Add GHCB definitions

Sean Christopherson
2020-08-03T18:17:36Z

On Mon, Aug 03, 2020 at 02:27:06PM +0200, Joerg Roedel wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
>
> Extend the vmcb_safe_area with SEV-ES fields and add a new
> 'struct ghcb' which will be used for guest-hypervisor communication.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
> arch/x86/include/asm/svm.h | 45 +++++++++++++++++++++++++++++++++++++-
> arch/x86/kvm/svm/svm.c | 2 ++
> 2 files changed, 46 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
> index 8a1f5382a4ea..9a3e0b802716 100644
> --- a/arch/x86/include/asm/svm.h
> +++ b/arch/x86/include/asm/svm.h
> @@ -200,13 +200,56 @@ struct __attribute__ ((__packed__)) vmcb_save_area {
> u64 br_to;
> u64 last_excp_from;
> u64 last_excp_to;
> +
> + /*
> + * The following part of the save area is valid only for
> + * SEV-ES guests when referenced through the GHCB.
> + */
> + u8 reserved_7[104];
> + u64 reserved_8; /* rax already available at 0x01f8 */
> + u64 rcx;
> + u64 rdx;
> + u64 rbx;
> + u64 reserved_9; /* rsp already available at 0x01d8 */
> + u64 rbp;
> + u64 rsi;
> + u64 rdi;
> + u64 r8;
> + u64 r9;
> + u64 r10;
> + u64 r11;
> + u64 r12;
> + u64 r13;
> + u64 r14;
> + u64 r15;
> + u8 reserved_10[16];
> + u64 sw_exit_code;
> + u64 sw_exit_info_1;
> + u64 sw_exit_info_2;
> + u64 sw_scratch;
> + u8 reserved_11[56];
> + u64 xcr0;
> + u8 valid_bitmap[16];
> + u64 x87_state_gpa;
> +};
> +
> +struct __attribute__ ((__packed__)) ghcb {

IMO this should use __packed straightaway, but I can also appreciate the
desire for consistency within a given snapshot in time so I'm a-ok if you
want to keep it as is.

> + struct vmcb_save_area save;
> + u8 reserved_save[2048 - sizeof(struct vmcb_save_area)];
> +
> + u8 shared_buffer[2032];
> +
> + u8 reserved_1[10];
> + u16 protocol_version; /* negotiated SEV-ES/GHCB protocol version */
> + u32 ghcb_usage;
> };
>
>
> static inline void __unused_size_checks(void)
> {
> - BUILD_BUG_ON(sizeof(struct vmcb_save_area) != 0x298);
> + BUILD_BUG_ON(sizeof(struct vmcb_save_area) != 1032);
> BUILD_BUG_ON(sizeof(struct vmcb_control_area) != 256);
> + BUILD_BUG_ON(sizeof(struct ghcb) != 4096);
> }
>
> struct __attribute__ ((__packed__)) vmcb {
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 783330d0e7b8..953cf947f022 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4161,6 +4161,8 @@ static struct kvm_x86_init_ops svm_init_ops __initdata = {
>
> static int __init svm_init(void)
> {
> + __unused_size_checks();
> +
> return kvm_init(&svm_init_ops, sizeof(struct vcpu_svm),
> __alignof__(struct vcpu_svm), THIS_MODULE);
> }
> --
> 2.17.1
>