Re: [PATCH v8 15/18] KVM: x86: Add guest support for detecting and enabling SEV Live Migration feature.

Steve Rutherford
2020-05-30T02:08:43Z

On Tue, May 5, 2020 at 2:20 PM Ashish Kalra <Ashish.Kalra@amd.com> wrote:
>
> From: Ashish Kalra <ashish.kalra@amd.com>
>
> The guest support for detecting and enabling SEV Live migration
> feature uses the following logic :
>
> - kvm_init_plaform() checks if its booted under the EFI
>
> - If not EFI,
>
> i) check for the KVM_FEATURE_CPUID
>
> ii) if CPUID reports that migration is support then issue wrmsrl
> to enable the SEV migration support
>
> - If EFI,
>
> i) Check the KVM_FEATURE_CPUID.
>
> ii) If CPUID reports that migration is supported, then reads the UEFI enviroment variable which
> indicates OVMF support for live migration.
>
> iii) If variable is set then wrmsr to enable the SEV migration support.
>
> The EFI live migration check is done using a late_initcall() callback.
>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---
> arch/x86/include/asm/mem_encrypt.h | 11 ++++++
> arch/x86/kernel/kvm.c | 62 ++++++++++++++++++++++++++++++
> arch/x86/mm/mem_encrypt.c | 11 ++++++
> 3 files changed, 84 insertions(+)
>
> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> index 848ce43b9040..d10e92ae5ca1 100644
> --- a/arch/x86/include/asm/mem_encrypt.h
> +++ b/arch/x86/include/asm/mem_encrypt.h
> @@ -20,6 +20,7 @@
>
> extern u64 sme_me_mask;
> extern bool sev_enabled;
> +extern bool sev_live_mig_enabled;
>
> void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr,
> unsigned long decrypted_kernel_vaddr,
> @@ -42,6 +43,8 @@ void __init sme_enable(struct boot_params *bp);
>
> int __init early_set_memory_decrypted(unsigned long vaddr, unsigned long size);
> int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size);
> +void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages,
> + bool enc);
>
> /* Architecture __weak replacement functions */
> void __init mem_encrypt_init(void);
> @@ -55,6 +58,7 @@ bool sev_active(void);
> #else /* !CONFIG_AMD_MEM_ENCRYPT */
>
> #define sme_me_mask 0ULL
> +#define sev_live_mig_enabled false
>
> static inline void __init sme_early_encrypt(resource_size_t paddr,
> unsigned long size) { }
> @@ -76,6 +80,8 @@ static inline int __init
> early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; }
> static inline int __init
> early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; }
> +static inline void __init
> +early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, bool enc) {}
>
> #define __bss_decrypted
>
> @@ -102,6 +108,11 @@ static inline u64 sme_get_me_mask(void)
> return sme_me_mask;
> }
>
> +static inline bool sev_live_migration_enabled(void)
> +{
> + return sev_live_mig_enabled;
> +}
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* __X86_MEM_ENCRYPT_H__ */
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 6efe0410fb72..4b29815de873 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -24,6 +24,7 @@
> #include <linux/debugfs.h>
> #include <linux/nmi.h>
> #include <linux/swait.h>
> +#include <linux/efi.h>
> #include <asm/timer.h>
> #include <asm/cpu.h>
> #include <asm/traps.h>
> @@ -403,6 +404,53 @@ static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
> early_set_memory_decrypted((unsigned long) ptr, size);
> }
>
> +#ifdef CONFIG_EFI
> +static bool setup_kvm_sev_migration(void)
> +{
> + efi_char16_t efi_Sev_Live_Mig_support_name[] = L"SevLiveMigrationEnabled";
> + efi_guid_t efi_variable_guid = MEM_ENCRYPT_GUID;
> + efi_status_t status;
> + unsigned long size;
> + bool enabled;
> +
> + if (!sev_live_migration_enabled())
> + return false;
> +
> + size = sizeof(enabled);
> +
> + if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
> + pr_info("setup_kvm_sev_migration: no efi\n");
> + return false;
> + }
> +
> + /* Get variable contents into buffer */
> + status = efi.get_variable(efi_Sev_Live_Mig_support_name,
> + &efi_variable_guid, NULL, &size, &enabled);
> +
> + if (status == EFI_NOT_FOUND) {
> + pr_info("setup_kvm_sev_migration: variable not found\n");
> + return false;
> + }
> +
> + if (status != EFI_SUCCESS) {
> + pr_info("setup_kvm_sev_migration: get_variable fail\n");
> + return false;
> + }
> +
> + if (enabled == 0) {
> + pr_info("setup_kvm_sev_migration: live migration disabled in OVMF\n");
> + return false;
> + }
> +
> + pr_info("setup_kvm_sev_migration: live migration enabled in OVMF\n");
> + wrmsrl(MSR_KVM_SEV_LIVE_MIG_EN, KVM_SEV_LIVE_MIGRATION_ENABLED);
> +
> + return true;
> +}
> +
> +late_initcall(setup_kvm_sev_migration);
> +#endif
> +
> /*
> * Iterate through all possible CPUs and map the memory region pointed
> * by apf_reason, steal_time and kvm_apic_eoi as decrypted at once.
> @@ -725,6 +773,20 @@ static void __init kvm_apic_init(void)
>
> static void __init kvm_init_platform(void)
> {
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
> + if (sev_active() &&
> + kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)) {
> + printk(KERN_INFO "KVM enable live migration\n");
> + sev_live_mig_enabled = true;
> + /*
> + * If not booted using EFI, enable Live migration support.
> + */
> + if (!efi_enabled(EFI_BOOT))
> + wrmsrl(MSR_KVM_SEV_LIVE_MIG_EN,
> + KVM_SEV_LIVE_MIGRATION_ENABLED);
> + } else
> + printk(KERN_INFO "KVM enable live migration feature unsupported\n");
> +#endif
> kvmclock_init();
> x86_platform.apic_post_init = kvm_apic_init;
> }
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index c9800fa811f6..f54be71bc75f 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -46,6 +46,8 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
>
> bool sev_enabled __section(.data);
>
> +bool sev_live_mig_enabled __section(.data);
> +
> /* Buffer used for early in-place encryption by BSP, no locking needed */
> static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE);
>
> @@ -204,6 +206,9 @@ static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,
> unsigned long sz = npages << PAGE_SHIFT;
> unsigned long vaddr_end, vaddr_next;
>
> + if (!sev_live_migration_enabled())
> + return;
> +
> vaddr_end = vaddr + sz;
>
> for (; vaddr < vaddr_end; vaddr = vaddr_next) {
> @@ -374,6 +379,12 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
> return early_set_memory_enc_dec(vaddr, size, true);
> }
>
> +void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages,
> + bool enc)
> +{
> + set_memory_enc_dec_hypercall(vaddr, npages, enc);
> +}
> +
> /*
> * SME and SEV are very similar but they are not the same, so there are
> * times that the kernel will need to distinguish between SME and SEV. The
> --
> 2.17.1
>

Reviewed-by: Steve Rutherford <srutherford@google.com>